Glucocorticoid Signaling and the Aging Heart

Glucocorticoid receptor signaling in the brain and its involvement in cognitive function

The hypothalamic-pituitary-adrenal axis regulates the secretion of glucocorticoids in response to environmental challenges. In the brain, a nuclear receptor transcription factor, the glucocorticoid receptor, is an important component of the hypothalamic-pituitary-adrenal axis's negative feedback loop and plays a key role in regulating cognitive equilibrium and neuroplasticity. The glucocorticoid receptor influences cognitive processes, including glutamate neurotransmission, calcium signaling, and the activation of brain-derived neurotrophic factor-mediated pathways, through a combination of genomic and non-genomic mechanisms. Protein interactions within the central nervous system can alter the expression and activity of the glucocorticoid receptor, thereby affecting the hypothalamic-pituitary-adrenal axis and stress-related cognitive functions. An appropriate level of glucocorticoid receptor expression can improve cognitive function, while excessive glucocorticoid receptors or long-term exposure to glucocorticoids may lead to cognitive impairment. Patients with cognitive impairment-associated diseases, such as Alzheimer's disease, aging, depression, Parkinson's disease, Huntington's disease, stroke, and addiction, often present with dysregulation of the hypothalamic-pituitary-adrenal axis and glucocorticoid receptor expression. This review provides a comprehensive overview of the functions of the glucocorticoid receptor in the hypothalamic-pituitary-adrenal axis and cognitive activities. It emphasizes that appropriate glucocorticoid receptor signaling facilitates learning and memory, while its dysregulation can lead to cognitive impairment. This provides clues about how glucocorticoid receptor signaling can be targeted to overcome cognitive disability-related disorders.

Molecular interactions of glucocorticoid and mineralocorticoid receptors define novel transcription and biological functions

Glucocorticoids are primary stress hormones necessary for life that function to maintain homeostasis. These hormones and their synthetic derivatives are widely used in the clinic to combat disease but are limited by development of resistance and by severe side effects. Understanding how glucocorticoids signal is crucial for developing safer and more effective glucocorticoids. Mechanistically glucocorticoid ligands induce glucocorticoid receptor (GR) homodimerization and regulation of gene expression. Here we show that GR and mineralocorticoid receptor (MR) form molecular complexes with distinct transcriptional responses that alter the biological roles of GR. MR inhibited GR interaction with genomic DNA and diminished glucocorticoid-regulated gene expression as well as suppressed cell apoptosis induced by GR signaling. Provocatively, multiple therapeutic glucocorticoids differentially induced the GR-MR interaction revealing unknown drug effects that are exploitable for fine-tuning glucocorticoid drug treatments. Molecular modeling of the GR-MR complex predicted an interaction interface residing in the LBD of both GR and MR. Mutation of a key amino acid in the interface of GR compromised GR - MR interaction without affecting GR activity in a gene reporter assay. Overall, our findings uncovered unique crosstalk mechanisms between distinct nuclear receptors providing a novel mechanism of diversity in the action of glucocorticoids that may contribute to context-dependent GR signaling in human health and disease.

Exploring Anti-Inflammatory Treatment as Upstream Therapy in the Management of Atrial Fibrillation

Inflammation has been widely recognized as one of the major pathophysiological drivers of the development of atrial fibrillation (AF), which works in tandem with other risk factors of AF including obesity, diabetes, hypertension, and heart failure (HF). Our current understanding of the role of inflammation in the natural history of AF remains elusive; however, several key players, including the NLRP3 (NLR family pyrin domain containing 3) inflammasome, have been acknowledged to be heavily influential on chronic inflammation in the atrial myocardium, which leads to fibrosis and eventual degradation of its electrical function. Nevertheless, our current methods of pharmacological modalities with reported immunomodulatory properties, including well-established classes of drugs e.g., drugs targeting the renin-angiotensin-aldosterone system (RAAS), statins, and vitamin D, have proven effective in reducing the overall risk of developing AF, the onset of postoperative atrial fibrillation (POAF), and reducing overall mortality among patients with AF. This might bring hope for further progress in developing new treatment modalities targeting cellular checkpoints of the NLRP3 inflammasome pathway, or revisiting other well-known anti-inflammatory drugs e.g., colchicine, vitamin C, nonsteroidal anti-inflammatory drugs (NSAIDs), glucocorticosteroids, and antimalarial drugs. In our review, we aim to find relevant upstream anti-inflammatory treatment methods for the management of AF and present the most current real-world evidence of their clinical utility.

Cardiometabolic Aspects of Congenital Adrenal Hyperplasia

Treatment of classic congenital adrenal hyperplasia (CAH) is directed at replacing deficient hormones and reducing androgen excess. However, even in the era of early diagnosis and lifelong hormonal substitution, the presence of CAH is still associated with numerous complications and also with increased mortality. The aim of this article was to create an authoritative and balanced review concerning cardiometabolic risk in patients with CAH. The authors searched all major databases and scanned reference lists of all potentially eligible articles to find relevant articles. The risk was compared with that in other forms of adrenal insufficiency. The reviewed articles, most of which were published recently, provided conflicting results, which can be partially explained by differences in the inclusion criteria and treatment, small sample sizes, and gene-environment interactions. However, many studies showed that the presence of CAH is associated with an increased risk of weight gain, worsening of insulin sensitivity, high blood pressure, endothelial dysfunction, early atherosclerotic changes in the vascular wall, and left ventricular diastolic dysfunction. These complications were more consistently reported in patients with classic than nonclassic CAH and were in part related to hormonal and functional abnormalities associated with this disorder and/or to the impact of overtreatment and undertreatment. An analysis of available studies suggests that individuals with classic CAH are at increased cardiometabolic risk. Excess cardiovascular and metabolic morbidity is likely multifactorial, related to glucocorticoid overtreatment, imperfect adrenal hormone replacement therapy, androgen excess, and adrenomedullary failure. Cardiometabolic effects of new therapeutic approaches require future targeted studies.

Glucocorticoids with or without fludrocortisone in septic shock: a narrative review from a biochemical and molecular perspective

Two randomised controlled trials have reported a reduction in mortality when adjunctive hydrocortisone is administered in combination with fludrocortisone compared with placebo in septic shock. A third trial did not support this finding when hydrocortisone administered in combination with fludrocortisone was compared with hydrocortisone alone. The underlying mechanisms for this mortality benefit remain poorly understood. We review the clinical implications and potential mechanisms derived from laboratory and clinical data underlying the beneficial role of adjunctive fludrocortisone with hydrocortisone supplementation in septic shock. Factors including distinct biological effects of glucocorticoids and mineralocorticoids, tissue-specific and mineralocorticoid receptor-independent effects of mineralocorticoids, and differences in downstream signalling pathways between mineralocorticoid and glucocorticoid binding at the mineralocorticoid receptor could contribute to this interaction. Furthermore, pharmacokinetic and pharmacodynamic disparities exist between aldosterone and its synthetic counterpart fludrocortisone, potentially influencing their effects. Pending publication of well-designed, randomised controlled trials, a molecular perspective offers valuable insights and guidance to help inform clinical strategies.

Glucocorticoids, their uses, sexual dimorphisms, and diseases: new concepts, mechanisms, and discoveries

The normal stress response in humans is governed by the hypothalamic-pituitary-adrenal (HPA) axis through heightened mechanisms during stress, raising blood levels of the glucocorticoid hormone cortisol. Glucocorticoids are quintessential compounds that balance the proper functioning of numerous systems in the mammalian body. They are also generated synthetically and are the preeminent therapy for inflammatory diseases. They act by binding to the nuclear receptor transcription factor glucocorticoid receptor (GR), which has two main isoforms (GRα and GRβ). Our classical understanding of glucocorticoid signaling is from the GRα isoform, which binds the hormone, whereas GRβ has no known ligands. With glucocorticoids being involved in many physiological and cellular processes, even small disruptions in their release via the HPA axis, or changes in GR isoform expression, can have dire ramifications on health. Long-term chronic glucocorticoid therapy can lead to a glucocorticoid-resistant state, and we deliberate how this impacts disease treatment. Chronic glucocorticoid treatment can lead to noticeable side effects such as weight gain, adiposity, diabetes, and others that we discuss in detail. There are sexually dimorphic responses to glucocorticoids, and women tend to have a more hyperresponsive HPA axis than men. This review summarizes our understanding of glucocorticoids and critically analyzes the GR isoforms and their beneficial and deleterious mechanisms and the sexual differences that cause a dichotomy in responses. We also discuss the future of glucocorticoid therapy and propose a new concept of dual GR isoform agonist and postulate why activating both isoforms may prevent glucocorticoid resistance.

Epigenetics of the far northern Yakutian population

BACKGROUND

Yakuts are one of the indigenous populations of the subarctic and arctic territories of Siberia characterized by a continental subarctic climate with severe winters, with the regular January average temperature in the regional capital city of Yakutsk dipping below - 40 °C. The epigenetic mechanisms of adaptation to such ecologies and environments and, in particular, epigenetic age acceleration in the local population have not been studied before.

RESULTS

This work reports the first epigenetic study of the Yakutian population using whole-blood DNA methylation data, supplemented with the comparison to the residents of Central Russia. Gene set enrichment analysis revealed, among others, geographic region-specific differentially methylated regions associated with adaptation to climatic conditions (water consumption, digestive system regulation), aging processes (actin filament activity, cell fate), and both of them (channel activity, regulation of steroid and corticosteroid hormone secretion). Further, it is demonstrated that the epigenetic age acceleration of the Yakutian representatives is significantly higher than that of Central Russia counterparts. For both geographic regions, we showed that epigenetically males age faster than females, whereas no significant sex differences were found between the regions.

CONCLUSIONS

We performed the first study of the epigenetic data of the Yakutia cohort, paying special attention to region-specific features, aging processes, age acceleration, and sex specificity.

Immunosuppressive Agents-Effects on the Cardiovascular System and Selected Metabolic Aspects: A Review

The widespread use of immunosuppressive drugs makes it possible to reduce inflammation in autoimmune diseases, as well as prevent transplant rejection in organ recipients. Despite their key action in blocking the body's immune response, these drugs have many side effects. These actions primarily affect the cardiovascular system, and the incidence of complications in patients using immunosuppressive drugs is significant, being associated with a higher incidence of cardiovascular incidents such as myocardial infarction and stroke. This paper analyzes the mechanisms of action of commonly used immunosuppressive drugs and their impact on the cardiovascular system. The adverse effect of immunosuppressive drugs is associated with toxicity within the cardiovascular system, which may be a problem in the clinical management of patients after transplantation. Immunosuppressants act on the cardiovascular system in a variety of ways, including fibrosis and myocardial remodeling, endothelium disfunction, hypertension, atherosclerosis, dyslipidemia or hyperglycaemia, metabolic syndrome, and hyperuricemia. The use of multidrug protocols makes it possible to develop regimens that can reduce the incidence of cardiovascular events. A better understanding of their mechanism of action and the range of complications could enable physicians to select the appropriate therapy for a given patient, as well as to reduce complications and prolong life.

Selective Modulation of the Keratoconic Stromal Microenvironment by FSH and LH

Keratoconus (KC) affects the corneal structure, with thinning and bulging outward into a conelike shape. Irregular astigmatism and decreased visual acuity appear during puberty and progress into the mid-30s, with unpredictable disease severity. The cause of KC is recognized as multifactorial, but remains poorly understood. Hormone imbalances are a significant modulator of the onset of KC. This study sought to investigate the role of gonadotropins, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in KC, using a three-dimensional, self-assembled matrix in vitro model. Healthy corneal fibroblasts and human KC cells in the corneal stroma were isolated, cultured, and stimulated with stable vitamin C to promote extracellular matrix assembly. Cultures were further stimulated with 2.5 or 10 mIU/mL FSH and 5 or 35 mIU/mL LH. Samples were evaluated for cell proliferation and morphology via BrdU assay and imaging; protein expression was assessed via Western blot analysis. Proliferation was significantly greater in human KC cells compared to healthy corneal fibroblasts with LH stimulation, but no changes were found with FSH stimulation. Additionally, in sex hormone receptors, fibrotic markers, proteoglycans, and members of the gonadotropin signaling pathway were significantly changed, largely driven by exogenous LH. The impact of exogenous FSH/LH in the KC stromal microenvironment was demonstrated. These results highlight the need to further examine the role of FSH/LH in KC and in human corneal homeostasis.

The accelerated organ senescence and proteotoxicity in thyrotoxicosis mice

The mechanism of aging has always been the focus of research, because aging is related to disease susceptibility and seriously affects people's quality of life. The diseases also accelerate the aging process, especially the pathological changes of substantive organs, such as cardiac hypertrophy, severely shortened lifespan. So, lesions in organs are both a consequence and a cause of aging. However, the disease in a given organ is not in isolation but is a systemic problem. Our previous study found that thyrotoxicosis mice model has aging characteristics including immunosenescence, lipotoxicity, malnutrition. But all these characteristics will lead to organ senescence, therefore, this study continued to study the aging changes of important organs such as heart, liver, and kidney in thyrotoxicosis mice using tandem mass tags (TMT) proteomics method. The results showed that the excess thyroxine led to cardiac hypertrophy. In the liver, the ability to synthesize functional proteins, detoxify, and metabolism were declined. The effect on the kidney was the decreased ability of detoxify and metabolism. The main finding of the present study was that the acceleration of organ senescence by excess thyroxine was due to proteotoxicity. The shared cause of proteotoxicity in the three organs included the intensify of oxidative phosphorylation, the redundancy production of ribosomes, and the lack of splicing and ubiquitin proteasome system function. Totally, proteotoxicity was another parallel between thyrotoxicosis and aging in addition to lipotoxicity. Our research provided a convenient and appropriate animal model for exploring aging mechanism and antiaging drugs.

Synergistic effects of hormones on structural and functional maturation of cardiomyocytes and implications for heart regeneration

The limited endogenous regenerative capacity of the human heart renders cardiovascular diseases a major health threat, thus motivating intense research on in vitro heart cell generation and cell replacement therapies. However, so far, in vitro-generated cardiomyocytes share a rather fetal phenotype, limiting their utility for drug testing and cell-based heart repair. Various strategies to foster cellular maturation provide some success, but fully matured cardiomyocytes are still to be achieved. Today, several hormones are recognized for their effects on cardiomyocyte proliferation, differentiation, and function. Here, we will discuss how the endocrine system impacts cardiomyocyte maturation. After detailing which features characterize a mature phenotype, we will contemplate hormones most promising to induce such a phenotype, the routes of their action, and experimental evidence for their significance in this process. Due to their pleiotropic effects, hormones might be not only valuable to improve in vitro heart cell generation but also beneficial for in vivo heart regeneration. Accordingly, we will also contemplate how the presented hormones might be exploited for hormone-based regenerative therapies.

CmPn/CmP Signaling Networks in the Maintenance of the Blood Vessel Barrier

Cerebral cavernous malformations (CCMs) arise when capillaries within the brain enlarge abnormally, causing the blood-brain barrier (BBB) to break down. The BBB serves as a sophisticated interface that controls molecular interactions between the bloodstream and the central nervous system. The neurovascular unit (NVU) is a complex structure made up of neurons, astrocytes, endothelial cells (ECs), pericytes, microglia, and basement membranes, which work together to maintain blood-brain barrier (BBB) permeability. Within the NVU, tight junctions (TJs) and adherens junctions (AJs) between endothelial cells play a critical role in regulating the permeability of the BBB. Disruptions to these junctions can compromise the BBB, potentially leading to a hemorrhagic stroke. Understanding the molecular signaling cascades that regulate BBB permeability through EC junctions is, therefore, essential. New research has demonstrated that steroids, including estrogens (ESTs), glucocorticoids (GCs), and metabolites/derivatives of progesterone (PRGs), have multifaceted effects on blood-brain barrier (BBB) permeability by regulating the expression of tight junctions (TJs) and adherens junctions (AJs). They also have anti-inflammatory effects on blood vessels. PRGs, in particular, have been found to play a significant role in maintaining BBB integrity. PRGs act through a combination of its classic and non-classic PRG receptors (nPR/mPR), which are part of a signaling network known as the CCM signaling complex (CSC). This network couples both nPR and mPR in the CmPn/CmP pathway in endothelial cells (ECs).

Glucocorticoid regulation of cancer development and progression

Glucocorticoids are steroid hormones that regulate a host of cellular and physiological functions. However, they are arguably best known for their potent anti-inflammatory properties. Chronic inflammation is well-known to promote the development and progression of numerous types of cancer, and emerging evidence suggests that glucocorticoid regulation of inflammation affects cancer development. However, the timing, intensity, and duration of glucocorticoid signaling have important but often contradictory effects on cancer development. Moreover, glucocorticoids are widely used in parallel with radiation and chemotherapy to control pain, dyspnea, and swelling, but their use may compromise anti-tumor immunity. This review will explore the effects of glucocorticoids on cancer development and progression with particular focus on pro and anti-tumor immunity.

Identification of glucocorticoid receptors as potential modulators of parasympathetic and sympathetic neurons within rat intracardiac ganglia

Background

Emerging evidences indicate that glucocorticoid receptors (GR) play a regulatory role in cardiac function, particularly with regard to the autonomic nervous system. Therefore, this study aimed to demonstrate the expression and the precise anatomical location of GR in relation to the parasympathetic and sympathetic innervations of the heart.

Methods

The present study used tissue samples from rat heart atria to perform conventional reverse-transcriptase polymerase chain reaction (RT-PCR), Western blot, and double immunofluorescence confocal analysis of GR with the neuronal markers vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP) as well as the mineralocorticoid receptor (MR).

Results

Double immunofluorescence labeling revealed that GRs were co-expressed with VAChT in parasympathetic principal neuronal somata and nerve terminals innervating atrium. Also, GR colocalized with the sympathetic neuronal marker TH in a cluster of small intensely fluorescent (SIF) cells, on intracardiac nerve terminals and in the atrial myocardium. GR immunoreactivity was scarcely identified on CGRP-immunoreactive sensory nerve terminals. Approximately 20% of GR immunoreactive neuronal somata co-localized with MR. Finally, conventional RT-PCR and Western blot confirmed the presence of GR and MR in rat heart atria.

Conclusion

This study provides evidence for the existence of GR predominantly on cardiac parasympathetic neurons and TH-immunoreactive SIF cells suggesting a functional role of cardiac GR on cardiovascular function by modulation of the cardiac autonomic nervous system.

Analysis of Genetic Variants in the Glucocorticoid Receptor Gene NR3C1 and Stenosis of the Carotid Artery in a Polish Population with Coronary Artery Disease

Background: Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Early diagnosis and elimination of risk factors are crucial for better managing CVDs. Atherosclerosis, whose development might be associated with glucocorticoids (GCs), is a critical factor in the development of carotid artery (CA) stenosis and most other CVDs. Aim: To investigate the association of Tth111I, N363S, and ER22/23EK-NR3C1 polymorphisms and the incidence of CA stenosis. Methods: The study group consisted of 117 patients diagnosed with coronary artery disease (CAD) and CA stenosis and 88 patients with CAD and ruled out CA stenosis. Genomic DNA was extracted from blood, and genotyping was carried out using Tth111I, N363S, and ER22/23EK-NR3C1 polymorphism sequencing. Results: No significant association between studied polymorphisms and the incidence or the severity of CA stenosis in the Polish population with CAD was found. Conclusion: This is the first study that proves that common NR3C1 gene variants do not influence CA stenosis and probably are not associated with atherosclerosis. The search for genes that can act as prognostic markers in predicting CA stenosis is still ongoing.

Endocrine Influence on Cardiac Metabolism in Development and Regeneration

Mammalian cardiomyocytes mostly utilize oxidation of fatty acids to generate ATP. The fetal heart, in stark contrast, mostly uses anaerobic glycolysis. During perinatal development, thyroid hormone drives extensive metabolic remodeling in the heart for adaptation to extrauterine life. These changes coincide with critical functional maturation and exit of the cell cycle, making the heart a post-mitotic organ. Here, we review the current understanding on the perinatal shift in metabolism, hormonal status, and proliferative potential in cardiomyocytes. Thyroid hormone and glucocorticoids have roles in adult cardiac metabolism, and both pathways have been implicated as regulators of myocardial regeneration. We discuss the evidence that suggests these processes could be interrelated and how this can help explain variation in cardiac regeneration across ontogeny and phylogeny, and we note what breakthroughs are still to be made.

Associations of Serum Cortisol with Cardiovascular Risk and Mortality in Patients Referred to Coronary Angiography

CONTEXT

Serum cortisol may be associated with cardiovascular risk factors and mortality in patients undergoing coronary angiography, but previous data on this topic are limited and controversial.

OBJECTIVE

We evaluated whether morning serum cortisol is associated with cardiovascular risk factors, lymphocyte subtypes, and mortality.

METHODS

This is a prospective cohort study performed at a tertiary care centre in south-west Germany between 1997 and 2000. We included 3052 study participants who underwent coronary angiography. The primary outcome measures were cardiovascular risk factors, lymphocyte subtypes, and all-cause and cardiovascular mortality.

RESULTS

Serum cortisol was associated with an adverse cardiovascular risk profile, but there was no significant association with coronary artery disease or acute coronary syndrome. In a subsample of 2107 participants, serum cortisol was positively associated with certain lymphocyte subsets, including CD16+CD56+ (natural killer) cells (P < 0.001). Comparing the fourth versus the first serum cortisol quartile, the crude Cox proportional hazard ratios (with 95% CIs) were 1.22 (1.00-1.47) for all-cause and 1.32 (1.04-1.67) for cardiovascular mortality, respectively. After adjustments for various cardiovascular risk factors, these associations were attenuated to 0.93 (0.76-1.14) for all-cause, and 0.97 (0.76-1.25) for cardiovascular mortality, respectively.

CONCLUSIONS

Despite significant associations with classic cardiovascular risk factors and natural killer cells, serum cortisol was not a significant and independent predictor of mortality in patients referred to coronary angiography. These findings might reflect that adverse cardiovascular effects of cortisol could be counterbalanced by some cardiovascular protective actions.

Hormonal control of cardiac regenerative potential

Research conducted across phylogeny on cardiac regenerative responses following heart injury implicates endocrine signaling as a pivotal regulator of both cardiomyocyte proliferation and heart regeneration. Three prominently studied endocrine factors are thyroid hormone, vitamin D, and glucocorticoids, which canonically regulate gene expression through their respective nuclear receptors thyroid hormone receptor, vitamin D receptor, and glucocorticoid receptor. The main animal model systems of interest include humans, mice, and zebrafish, which vary in cardiac regenerative responses possibly due to the differential onsets and intensities of endocrine signaling levels throughout their embryonic to postnatal organismal development. Zebrafish and lower vertebrates tend to retain robust cardiac regenerative capacity into adulthood while mice and other higher vertebrates experience greatly diminished cardiac regenerative potential in their initial postnatal period that is sustained throughout adulthood. Here, we review recent progress in understanding how these three endocrine signaling pathways regulate cardiomyocyte proliferation and heart regeneration with a particular focus on the controversial findings that may arise from different assays, cellular-context, age, and species. Further investigating the role of each endocrine nuclear receptor in cardiac regeneration from an evolutionary perspective enables comparative studies between species in hopes of extrapolating the findings to novel therapies for human cardiovascular disease.