Dexamethasone induces transcriptional activation of Bcl-xL gene and inhibits cardiac injury by myocardial ischemia

Efficacy of preoperative single-dose dexamethasone in preventing postoperative pulmonary complications following minimally invasive esophagectomy: a retrospective propensity score-matched study

BACKGROUND

The study was performed to investigate the efficacy and safety of preoperative dexamethasone (DXM) in preventing postoperative pulmonary complications (PPCs) after minimally invasive esophagectomy (MIE).

METHODS

Patients who underwent total MIE with two-field lymph node dissection from February 2018 to February 2023 were included in this study. Patients who were given either 5 mg or 10 mg DXM as preoperative prophylactic medication before induction of general anesthesia were assigned to the DXM group, while patients who did not receive DXM were assigned to the control group. Preoperative evaluations, intraoperative data, and occurrence of postoperative complications were analyzed. The primary outcome was the incidence of PPCs occurring by day 7 after surgery.

RESULTS

In total, 659 patients were included in the study; 453 patients received preoperative DXM, while 206 patients did not. Propensity score-matched analysis created a matched cohort of 366 patients, with 183 patients each in the DXM and control groups. A total of 24.6% of patients in the DXM group and 30.6% of patients in the control group had PPCs (P = 0.198). The incidence of respiratory failure was significantly lower in the DXM group than in the control group (1.1% vs 5.5%, P = 0.019). Fewer patients were re-intubated during their hospital stay in the DXM group than in the control group (1.1% vs 5.5%, P = 0.019).

CONCLUSIONS

Preoperative DXM before induction of anesthesia did not reduce overall PPC development after MIE. Nevertheless, the occurrence of early respiratory failure and the incidence of re-intubation during hospitalization were decreased.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (No. ChiCTR2300071674; Date of registration, 22/05/2023).

Effects of prenatal dexamethasone exposure on adult C57BL/6J mouse metabolism and oxidative stress

Prenatal glucocorticoid exposure has been shown to alter hypothalamic-pituitary-adrenal axis function resulting in altered fetal development that can persist through adulthood. Fetal exposure to excess dexamethasone, a synthetic glucocorticoid, has been shown to alter adult behaviour and metabolism. This study investigated the effects prenatal dexamethasone exposure had on adult offspring cardiac and liver metabolism and oxidative stress. Pregnant C57BL/6 mice received a dose of 0.4 mg/kg dexamethasone on gestational days 15-17. Once pups were approximately 7 months old, glucose uptake was determined using positron emission tomography and insulin resistance (IR) was determined by homeostatic model assessment (HOMA) IR calculation. Oxidative stress was assessed by measuring 4-hydroxynonenal protein adduct formation and total reactive oxygen species. Female dexamethasone group had significantly increased glucose uptake when insulin stimulated compared to vehicle-treated mice. HOMA IR revealed no evidence of IR in either male or female offspring. There was also no change in oxidative stress markers in either cardiac or liver tissues of male or female offspring. These data suggest that prenatal dexamethasone exposure in male mice does not alter oxidative stress or metabolism. However, prenatal dexamethasone exposure increased glucocorticoids, cardiac glucose uptake, and pAkt signaling in female heart tissues in adult mice, suggesting there are sex differences in prenatal dexamethasone exposure.

Glucocorticoid Receptor Antagonism and Cardiomyocyte Regeneration Following Myocardial Infarction: A Systematic Review

Myocardial regeneration has been a topic of interest in literature and research in recent years. An evolving approach reported is glucocorticoid (GC) receptor antagonism and its role in the regeneration of cardiomyocytes. The authors of this study aim to explore the reported literature on GC receptor antagonism and its effects on cardiomyocyte remodeling, hypertrophy, scar formation, and ongoing cardiomyocyte death following cardiac injury. This article overviews cellular biology, mechanisms of action, clinical implications, challenges, and future considerations. The authors of this study conducted a systematic review utilizing the Cochrane methodology and PRISMA guidelines. This study includes data collected and interpreted from 30 peer-reviewed articles from 3 databases with the topic of interest. The mammalian heart has regenerative potential during its embryonic and fetal phases which is lost during its developmental processes. The microenvironment, intrinsic molecular mechanisms, and systemic and external factors impact cardiac regeneration. GCs influence these aspects in some cases. Consequently, GC receptor antagonism is emerging as a promising potential target for stimulating endogenous cardiomyocyte proliferation, aiding in cardiomyocyte regeneration following a cardiac injury such as a myocardial infarction (MI). Experimental studies on neonatal mice and zebrafish have shown promising results with GC receptor ablation (or brief pharmacological antagonism) promoting the survival of myocardial cells, re-entry into the cell cycle, and cellular division, resulting in cardiac muscle regeneration and diminished scar formation. Transient GC receptor antagonism has the potential to stimulate cardiomyocyte regeneration and help prevent the dreaded complications of MI. More trials based on human populations are encouraged to justify their applications and weigh the risk-benefit ratio.

Long-term Dexamethasone Treatment Increases Cardiac Galectin-3 Levels

PURPOSE

Glucocorticoids, which are widely prescribed around the world, cause cardiac remodeling in long-term treatment by triggering insulin resistance and increasing blood pressure. However, its role in cardiac remodeling remains unclear. Galectin-3 (gal-3) is a member of a beta-galactoside-binding animal lectins, upregulated as a result of insulin resistance and in the pressure-overloaded myocardium and regulate cardiac remodeling. We hypothesized that gal-3 may be upregulated in the myocardium with prolonged use of glucocorticoids and associated with cardiac hypertrophy.

METHODS

To examine the involvement of glucocorticoids in gal-3 levels in rat myocardium, sixteen female Wistar Albino rats were assigned to control (C; n = 8) and dexamethasone (Dex; n = 8) groups. Daily dexamethasone was injected subcutaneously for 28 days at a dose of 1 mg.kg-1. Control animals were injected with the same volume of saline. The body weight and heart weights were determined. Gal-3 levels in myocardium were determined by Western blot.

RESULTS

Our data shows that dexamethasone administration resulted in significant increase in heart weight (p < 0.05) and HW/BW ratios (p < 0.001) and 28 days of dexamethasone administration with the dose of 1 mg.kg-1 caused a twofold increase in the gal-3 expression in the left ventricle (p < 0.001).

CONCLUSION

The finding of the current study is the first to show that dexamethasone causes an increase in gal-3 levels in myocardium. Our study provides an important step in the development of possible therapeutics by determining that dexamethasone causes an increase in gal-3 levels in the myocardium and raises awareness about the follow-up of patients receiving long-term glucocorticoid therapy.

Effect of Dexamethasone on Myocardial Injury After Total Knee Arthroplasty: A Substudy of the Randomized Clinical DEX-2-TKA Trial

BACKGROUND

Myocardial injury after noncardiac surgery (MINS) carries a high postoperative mortality. In this preplanned, subgroup analysis of the randomized DEX-2-TKA Trial, we investigated the effect of dexamethasone versus placebo on the concentration of cardiac troponin I and T (TnI and TnT) on the first postoperative morning after total knee arthroplasty. In addition, frequency of MINS, myocardial infarction, and major adverse cardiovascular events where evaluated.

METHODS

We included 290 patients who received either 24 mg of dexamethasone intravenously (given perioperatively) or placebo. Blood samples were analyzed as either TnI or T depending on trial site.

RESULTS

A total of 236 samples were eligible for analysis of TnI and 38 samples for TnT on the first postoperative morning. The median (IQR) TnI concentration was 4.6 ng/L (0-7.2 ng/L) in the dexamethasone group and 4.5ng/l (0-7.0 ng/L) in the placebo group (P = .96) on the first postoperative morning. The median TnT was 9 ng/L (6-11 ng/L) in the dexamethasone group and 8 ng/L (5-10 ng/L) in the placebo group (P = .68). The frequencies of MINS, myocardial infarction, and major adverse cardiovascular events were similar in the compared groups, but these analyses were underpowered.

CONCLUSION

We found no effect of dexamethasone on postoperative concentration of troponin I or T on the first postoperative morning after total knee arthroplasty.

Benefits of combined exercise training on arterial stiffness and blood pressure in spontaneously hypertensive rats treated or not with dexamethasone

Dexamethasone (DEX)-induced arterial stiffness is an important side-effect, associated with hypertension and future cardiovascular events, which can be counteracted by exercise training. The aim of this study was to evaluate the mechanisms induced by combined training to attenuate arterial stiffness and hypertension in spontaneously hypertensive rats treated or not with dexamethasone. Spontaneously hypertensive rats (SHR) underwent combined training for 74 days and were treated with dexamethasone (50 µg/kg s. c.) or saline solution during the last 14 days. Wistar rats were used as controls. Echocardiographic parameters, blood pressure (BP) and pulse wave velocity (PWV), as well as histological analyses of the heart and aorta, carotid and femoral arteries were performed. At the beginning, SHR had higher BP and PWV compared with Wistar rats. After 60 days, while BP increased in sedentary SHR, combined exercise training decreased BP and PWV. After 74d, the higher BP and PWV of sedentary SHR was accompanied by autonomic imbalance to the heart, cardiac remodeling, and higher arterial collagen deposition. DEX treatment did not change these parameters. On the other hand, trained SHR had reduced BP and PWV, which was associated with better autonomic balance to the heart, reduced myocardial collagen deposition, as well as lower arterial collagen deposition. The results of this study suggest that combined training, through the reduction of aortic collagen deposition, is an important strategy to reduce arterial stiffness in spontaneously hypertensive rats, and these lower responses were maintained regardless of dexamethasone treatment.

Histone methyltransferase KMT2D contributes to the protection of myocardial ischemic injury

Histone H3 lysine 4 (H3K4) methyltransferase 2D (KMT2D) plays an important role in cell development in early life. However, the function of KMT2D in adult cells such as cardiomyocytes or neurons has not been reported. In this study, cardiomyocyte-specific KMT2D knockout (KMT2D-cKO) and control (KMT2D-Ctl) mice were exposed to sham or myocardial ischemia (MI) surgery. Depletion of KMT2D aggravated the ischemic area, led to the increased mortality (26.5% in KMT2D-cKO vs 12.5% in KMT2D-Ctl) of the mice, and weakened the left ventricular systolic function. RNA-seq analysis in cardiac tissues identified genes whose expression was changed by MI and KMT2D deletion. Combined with the genome-wide association study (GWAS) analysis, cardiac disease-associated genes Rasd1, Thsd7a, Ednra, and Tns1 were identified. The expression of the Rasd1 was significantly decreased by MI or the loss of KMT2D in vivo. Meanwhile, ChIP assays demonstrated that either MI or loss of KMT2D attenuated monomethylated H3K4 (H3K4me1) enrichment on the enhancer of Rasd1. By generating a KMT2D knockout (H9C2-KO) H9C2 monoclone, we verified that the expression of Rasd1 was controlled by KMT2D, and the expression of Rasd1 was decreased by serum starvation but not low-(O₂) treatment in H9C2 cells. KMT2D has a protective effect on ischemic myocardium by regulating cardiac disease-associated genes including Rasd1. KMT2D is required for the H3K4me1 deposition on the enhancer of Rasd1. Our data for the first time suggest that KMT2D-mediated Rasd1 expression may play an important protective effect on adult cells during nutritional deficiency caused by ischemic injury.

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.

Dexamethasone Alleviates Myocardial Injury in a Rat Model of Acute Myocardial Infarction Supported by Venoarterial Extracorporeal Membrane Oxygenation

Myocardial ischemia causes myocardial inflammation. Research indicates that the venoarterial extracorporeal membrane oxygenation (VA ECMO) provides cardiac support; however, the inflammatory response caused by myocardial ischemia remains unresolved. Dexamethasone (Dex), a broad anti-inflammatory agent, exhibits a cardioprotective effect. This study aims to investigate the effect of Dex on a rat model of acute myocardial infarction (AMI) supported by VA ECMO. Male Sprague-Dawley rats (300–350 g) were randomly divided into three groups: Sham group (n = 5), ECMO group (n = 6), and ECMO + Dex group (n = 6). AMI was induced by ligating the left anterior descending (LAD) coronary artery. Sham group only thoracotomy was performed but LAD was not ligated. The ECMO and ECMO + Dex groups were subjected to 1 h of AMI and 2 h of VA ECMO. In the ECMO + Dex group, Dex (0.2 mg/kg) was intravenously injected into the rats after 1 h of AMI. Lastly, myocardial tissue and blood samples were harvested for further evaluation. The ECMO + Dex group significantly reduced infarct size and levels of cTnI, cTnT, and CK-MB. Apoptotic cells and the expression levels of Bax, Caspase3, and Cle-Caspase3 proteins were markedly lower in the ECMO + Dex group than that in the ECMO group. Neutrophil and macrophage infiltration was lower in the ECMO + Dex group than in the ECMO group. A significant reduction was noted in ICAM-1, C5a, MMP-9, IL-1β, IL-6, and TNF-α. In summary, our findings revealed that Dex alleviates myocardial injury in a rat model of AMI supported by VA ECMO.

The Development of Novel Drug Treatments for Stroke Patients: A Review

Acute ischemic stroke is a critical condition that can result in disability and death. The consequences of this medical condition depend on various factors, including the size of the stroke, affected brain region, treatment onset, and the type of treatment. The primary objective of stroke treatment is to restart ischemic penumbra tissue perfusion and reduce infarct volume by sustaining blood flow. Recent research on the condition’s pathological pathways and processes has significantly improved treatment options beyond restoring perfusion. Many studies have concentrated on limiting injury severity via the manipulation of molecular mechanisms of ischemia, particularly in animal research. This article reviews completed and ongoing research on the development of acute ischemic stroke drugs. This study focuses on three main categories of antithrombotic drugs, thrombolytic drugs, and neuroprotective agents. The paper outlines findings from animal and clinical trials and explores the working mechanisms of these drugs.

Corticosteroid plus glycyrrhizin therapy for chronic drug- or herb-induced liver injury achieves biochemical and histological improvements: a randomised open-label trial

BACKGROUND

Treatment of chronic drug-induced liver injury (DILI) or herb-induced liver injury(HILI) is an important and unresolved challenge. There is no consensus regarding the indications for corticosteroids for chronic DILI/HILI.

AIMS

To investigate the efficacy and safety of corticosteroid plus glycyrrhizin for patients with chronic DILI/HILI.

METHODS

This was a randomised open-label trial. Eligible patients with causality assessment using the updated RUCAM were randomly assigned (1:1) either to the steroid treatment group (48-week stepwise dose reduction of methylprednisolone plus glycyrrhizin) or control group (glycyrrhizin alone). Liver biopsies were performed at baseline and at the end of the 48-week treatment period. The primary outcome was the proportion of patients with sustained biochemical response (SBR). The secondary outcomes were improvement in liver histology, time to biochemical normalisation and safety.

RESULTS

Of 80 participants, 70 (87.5%) completed the trial. The patients were predominantly female (77.5%), aged >40 years (77.5%) and had a hepatocellular injury pattern of DILI (71.2%). Compared to the control group, the treatment group showed a higher proportion of SBR (94.3% vs. 71.4%, p = 0.023), shorter biochemical normalisation time and histological improvements in both histological activity and fibrosis. The DILI and HILI subgroups, as well as the autoimmune hepatitis (AIH)-like DILI and non-AIH-like subgroups, showed comparable responses. No severe adverse events were observed during the trial.

CONCLUSION

This study provides the first clinical evidence that corticosteroid plus glycyrrhizin therapy for chronic DILI with or without AIH-like features can achieve both biochemical response and histological improvements with good safety. (ClinicalTrials.gov, NCT02651350).

Chemotherapy-Free Targeted Anti-BCR-ABL+ Acute Lymphoblastic Leukemia Therapy May Benefit the Heart

Simple Summary

Risk-adapted multiagent chemotherapy has led to a remarkable improvement in the life expectancy of patients with acute lymphoblastic leukemia (ALL). Nevertheless, in high-risk subgroups such as BCR-ABL+ ALL, relapse rates remain high without allogeneic hematopoietic stem cell transplantation, and the adverse effects of chemotherapy may cause acute and chronic cardiac complications or dysfunction. Here, we demonstrated that chemotherapy-free targeted therapies designed to optimize apoptosis induction in BCR-ABL+ ALL may circumvent cardiac on-target side effects and may even activate cardiac recovery.

Abstract

Targeted therapies are currently considered the best cost–benefit anti-cancer treatment. In hematological malignancies, however, relapse rates and non-hematopoietic side effects including cardiotoxicity remain high. Here, we describe significant heart damage due to advanced acute lymphoblastic leukemia (ALL) with t(9;22) encoding the bcr-abl oncogene (BCR-ABL+ ALL) in murine xenotransplantation models. Echocardiography reveals severe cardiac dysfunction with impaired left ventricular function and reduced heart and cardiomyocyte dimensions associated with increased apoptosis. This cardiac damage is fully reversible, but cardiac recovery depends on the therapy used to induce ALL remission. Chemotherapy-free combination therapy with dasatinib (DAS), venetoclax (VEN) (targeting the BCR-ABL oncoprotein and mitochondrial B-cell CLL/Lymphoma 2 (BCL2), respectively), and dexamethasone (DEX) can fully revert cardiac defects, whereas the depletion of otherwise identical ALL in a genetic model using herpes simplex virus type 1 thymidine kinase (HSV-TK) cannot. Mechanistically, dexamethasone induces a pro-apoptotic BCL2-interacting mediator of cell death (BIM) expression and apoptosis in ALL cells but enhances pro-survival B-cell lymphoma extra-large (BCLXL) expression in cardiomyocytes and clinical recovery with the reversion of cardiac atrophy. These data demonstrate that therapies designed to optimize apoptosis induction in ALL may circumvent cardiac on-target side effects and may even activate cardiac recovery. In the future, combining the careful clinical monitoring of cardiotoxicity in leukemic patients with the further characterization of organ-specific side effects and signaling pathways activated by malignancy and/or anti-tumor therapies seems reasonable.

Corticosteroid Receptors in Cardiac Health and Disease

Nuclear receptors play a central role in both energy metabolism and cardiomyocyte death and survival in the heart. Recent evidence suggests they may also influence cardiomyocyte endowment. Although several members of the nuclear receptor family play key roles in heart maturation (including thyroid hormone receptors) and cardiac metabolism, here, the focus will be on the corticosteroid receptors, the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). The heart is an important target for the actions of corticosteroids, yet the homeostatic role of GR and MR in the healthy heart has been elusive. However, MR antagonists are important in the treatment of heart failure, a condition associated with mitochondrial dysfunction and energy failure in cardiomyocytes leading to mitochondria-initiated cardiomyocyte death (Ingwall and Weiss, Circ Res 95:135-145, 2014; Ingwall , Cardiovasc Res 81:412-419, 2009; Zhou and Tian , J Clin Invest 128:3716-3726, 2018). In contrast, animal studies suggest GR activation in cardiomyocytes has a cardioprotective role, including in heart failure.

Cyanide Poisoning Compromises Gene Pathways Modulating Cardiac Injury in Vivo

Smoke inhalation from a structure fire is a common route of cyanide poisoning in the U.S. Cyanide inhibits cellular respiration, often leading to death. Its rapid distribution throughout the body can result in injuries to multiple organs, and cyanide victims were reported to experience myocardial infarction and other cardiac complications. However, molecular mechanisms of such complications are yet to be elucidated. While FDA-approved CN antidotes such as sodium thiosulfate and hydroxocobalamin are clinically used, they have foreseeable limitations during mass casualty situations because they require intravenous administration. To facilitate the development of better antidotes and therapeutic treatments, a global view of molecular changes induced by cyanide exposure is necessary. As an exploratory pursuit, we performed oligonucleotide microarrays to establish cardiac transcriptomes of an animal model of nose-only inhalation exposure to hydrogen cyanide (HCN), which is relevant to smoke inhalation. We also profiled cardiac transcriptomes after subcutaneous injection of potassium cyanide (KCN). Although the KCN injection model has often been used to evaluate medical countermeasures, this study demonstrated that cardiac transcriptomes are largely different from that of the HCN inhalation model at multiple time points within 24 h after exposure. Pathway analysis identified that HCN-induced transcriptomes were enriched with genes encoding mediators of pathways critical in modulation of cardiac complications and that a large number of such genes were significantly decreased in expression. We utilized the upstream regulatory analysis to propose drugs that can be potentially employed to treat cyanide-induced cardiac complications.

Differential effects of dexamethasone on arterial stiffness, myocardial remodeling and blood pressure between normotensive and spontaneously hypertensive rats

Dexamethasone (DEX)-induced hypertension is observed in normotensive rats, but little is known about the effects of DEX on spontaneously hypertensive animals (SHR). This study aimed to evaluate the effects of DEX on hemodynamics, cardiac hypertrophy and arterial stiffness in normotensive and hypertensive rats. Wistar rats and SHR were treated with DEX (50 μg/kg s.c., 14 d) or saline. Pulse wave velocity (PWV), echocardiographic parameters, blood pressure (BP), autonomic modulation and histological analyses of heart and thoracic aorta were performed. SHR had higher BP compared with Wistar, associated with autonomic unbalance to the heart. Echocardiographic changes in SHR (vs. Wistar) were suggestive of cardiac remodeling: higher relative wall thickness (RWT, +28%) and left ventricle mass index (LVMI, +26%) and lower left ventricle systolic diameter (LVSD, -19%) and LV diastolic diameter (LVDD, -10%), with slightly systolic dysfunction and preserved diastolic dysfunction. Also, SHR had lower myocardial capillary density and similar collagen deposition area. PWV was higher in SHR due to higher aortic collagen deposition. DEX-treated Wistar rats presented higher BP (~23%) and autonomic unbalance. DEX did not change cardiac structure in Wistar, but PWV (+21%) and aortic collagen deposition area (+21%) were higher compared with control. On the other side, DEX did not change BP or autonomic balance to the heart in SHR, but reduced RWT and LV collagen deposition area (-12% vs. SHR_CT ). In conclusion, the results suggest a differential effect of dexamethasone on arterial stiffness, myocardial remodeling and blood pressure between normotensive and spontaneously hypertensive rats.

Quantitative evaluation of dexamethasone treatment effects in renal ischemia-reperfusion injury using contrast enhanced ultrasonography in rats

BACKGROUND

Renal ischemia-reperfusion (I/R) injury often occurs in various clinical events, and its incidence and mortality have been increasing.

OBJECTIVE

To investigate the value of contrast enhanced ultrasonography (CEUS) in the monitoring of dexamethasone in the improvement of renal I/R injury in rats.

METHODS

Eighteen healthy male Sprague-Dawley rats were randomly divided into sham-operated, I/R, and I/R surgery plus dexamethasone treatment (Dexa) groups. In the I/R group 45-minute renal ischemia with 24 h reperfusion period was monitored. Time-intensity curve (TIC)-derived parameters, which included peak value, time to peak (TP), area under the curve (AUC), and mean transit time (MTT) were compared to the blood creatinine, urea, Caspase-1, and NLRP3 levels.

RESULTS

The I/R group showed an increased peak value, prolonged TP and MTT, and greater AUC (P < 0.05). The Dexa group showed shorter TP and MTT, and smaller AUC (P < 0.05). Results show that the associations between (i) TP, AUC, and MTT and (ii) creatinine, urea, Caspase-1, and NLRP3 levels were significant (P < 0.05).

CONCLUSION

Dexamethasone can alleviate renal I/R injury in rats, which may be related to the inhibition of NLRP3 and caspase-1. CEUS can quantitatively measure this change, in which the changes in TP, AUC and MMT values have considerable reference values.

Dexamethasone and Training-Induced Cardiac Remodeling Improve Cardiac Function and Arterial Pressure in Spontaneously Hypertensive Rats

INTRODUCTION

Dexamethasone (DEX)-induced hypertension and cardiac remodeling are still unclear, especially in spontaneously hypertensive rats (SHR). On the other side, exercise training is a good strategy to control hypertension. Therefore, this study investigated the effects of DEX treatment and physical training on arterial pressure and cardiac remodeling in SHR.

MATERIAL AND METHODS

SHR underwent treadmill training (5 days/week, 1h/session, at 50-60% of maximal capacity, 0% degree, 75 days) and received low-dose of DEX (50µg/kg, s.c.) during the last 15 days. Sedentary Wistar rats (W) were used as control. Echocardiography and artery catheterization were performed for cardiac remodeling and function, arterial pressure and autonomic nervous system analyses. In addition, left ventricle (LV) capillary density, myocyte diameter and collagen deposition area were analyzed using specific histological staining.

RESULTS

Low-dose of DEX treatment did not exacerbate arterial pressure of SHR and trained groups had lower values, regardless of DEX. DEX and training decreased relative left ventricle wall thickness (RWT) and determined LV angiogenesis (+19%) and lower collagen deposition area (-22%). In addition, it determined increased left ventricular diastolic diameter. These changes were followed by improvements on systolic and diastolic function, since it was observed increased posterior wall shortening velocity (PWSV) and reduced isovolumetric relaxation time (IVRT).

CONCLUSION

In conclusion, this study is unique to indicate that low-dose of DEX treatment does not exacerbate arterial pressure in SHR and, when associated with training, it improves LV systolic and diastolic function, which may be due to LV angiogenesis and reduction of wall collagen deposition area.

Bioactive Lipid Signaling in Cardiovascular Disease, Development, and Regeneration

Cardiovascular disease (CVD) remains a leading cause of death globally. Understanding and characterizing the biochemical context of the cardiovascular system in health and disease is a necessary preliminary step for developing novel therapeutic strategies aimed at restoring cardiovascular function. Bioactive lipids are a class of dietary-dependent, chemically heterogeneous lipids with potent biological signaling functions. They have been intensively studied for their roles in immunity, inflammation, and reproduction, among others. Recent advances in liquid chromatography-mass spectrometry techniques have revealed a staggering number of novel bioactive lipids, most of them unknown or very poorly characterized in a biological context. Some of these new bioactive lipids play important roles in cardiovascular biology, including development, inflammation, regeneration, stem cell differentiation, and regulation of cell proliferation. Identifying the lipid signaling pathways underlying these effects and uncovering their novel biological functions could pave the way for new therapeutic strategies aimed at CVD and cardiovascular regeneration.

ROS-responsive polyurethane fibrous patches loaded with methylprednisolone (MP) for restoring structures and functions of infarcted myocardium in vivo

Reactive oxygen species (ROS) play an important role in the pathogenesis of numerous diseases including atherosclerosis, diabetes, inflammation and myocardial infarction (MI). In this study, a ROS-responsive biodegradable elastomeric polyurethane containing thioketal (PUTK) linkages was synthesized from polycaprolactone diol (PCL-diol ), 1,6-hexamethylene diisocyanate (HDI), and ROS-cleavable chain extender. The PUTK was electrospun into fibrous patches with the option to load glucocorticoid methylprednisolone (MP), which were then used to treat MI of rats in vivo. The fibrous patches exhibited suitable mechanical properties and high elasticity. The molecular weight of PUTK was decreased significantly after incubation in 1 mM H₂O₂ solution for 2 weeks due to the degradation of thioketal bonds on the polymer backbone. Both the PUTK and PUTK/MP fibrous patches showed good antioxidant property in an oxidative environment in vitro. Implantation of the ROS-responsive polyurethane patches in MI of rats in vivo could better protect cardiomyocytes from death in the earlier stage (24 h) than the non ROS-responsive ones. Implantation of the PUTK/MP fibrous patches for 28 days could effectively improve the reconstruction of cardiac functions including increased ejection fraction, decreased infarction size, and enhanced revascularization of the infarct myocardium.

Glucocorticoids preserve the t-tubular system in ventricular cardiomyocytes by upregulation of autophagic flux

A major contributor to contractile dysfunction in heart failure is remodelling and loss of the cardiomyocyte transverse tubular system (t-system), but underlying mechanisms and signalling pathways remain elusive. It has been shown that dexamethasone promotes t-tubule development in stem cell-derived cardiomyocytes and that cardiomyocyte-specific glucocorticoid receptor (GR) knockout (GRKO) leads to heart failure. Here, we studied if the t-system is altered in GRKO hearts and if GR signalling is required for t-system preservation in adult cardiomyocytes. Confocal and 3D STED microscopy of myocardium from cardiomyocyte-specific GRKO mice revealed decreased t-system density and increased distances between ryanodine receptors (RyR) and L-type Ca²⁺ channels (LTCC). Because t-system remodelling and heart failure are intertwined, we investigated the underlying mechanisms in vitro. Ventricular cardiomyocytes from failing human and healthy adult rat hearts cultured in the absence of glucocorticoids (CTRL) showed distinctively lower t-system density than cells treated with dexamethasone (EC₅₀ 1.1 nM) or corticosterone. The GR antagonist mifepristone abrogated the effect of dexamethasone. Dexamethasone improved RyR-LTCC coupling and synchrony of intracellular Ca²⁺ release, but did not alter expression levels of t-system-associated proteins junctophilin-2 (JPH2), bridging integrator-1 (BIN1) or caveolin-3 (CAV3). Rather, dexamethasone upregulated LC3B and increased autophagic flux. The broad-spectrum protein kinase inhibitor staurosporine prevented dexamethasone-induced upregulation of autophagy and t-system preservation, and autophagy inhibitors bafilomycin A and chloroquine accelerated t-system loss. Conversely, induction of autophagy by rapamycin or amino acid starvation preserved the t-system. These findings suggest that GR signalling and autophagy are critically involved in t-system preservation and remodelling in the heart.

The Glucocorticoid Receptor in Cardiovascular Health and Disease

The glucocorticoid receptor is a member of the nuclear receptor family that controls many distinct gene networks, governing various aspects of development, metabolism, inflammation, and the stress response, as well as other key biological processes in the cardiovascular system. Recently, research in both animal models and humans has begun to unravel the profound complexity of glucocorticoid signaling and convincingly demonstrates that the glucocorticoid receptor has direct effects on the heart and vessels in vivo and in vitro. This research has contributed directly to improving therapeutic strategies in human disease. The glucocorticoid receptor is activated either by the endogenous steroid hormone cortisol or by exogenous glucocorticoids and acts within the cardiovascular system via both genomic and non-genomic pathways. Polymorphisms of the glucocorticoid receptor are also reported to influence the progress and prognosis of cardiovascular disease. In this review, we provide an update on glucocorticoid signaling and highlight the critical role of this signaling in both physiological and pathological conditions of the cardiovascular system. With increasing in-depth understanding of glucocorticoid signaling, the future is promising for the development of targeted glucocorticoid treatments and improved clinical outcomes.

Anti-inflammatory therapies in myocardial infarction: failures, hopes and challenges

In the infarcted heart, the damage-associated molecular pattern proteins released by necrotic cells trigger both myocardial and systemic inflammatory responses. Induction of chemokines and cytokines and up-regulation of endothelial adhesion molecules mediate leukocyte recruitment in the infarcted myocardium. Inflammatory cells clear the infarct of dead cells and matrix debris and activate repair by myofibroblasts and vascular cells, but may also contribute to adverse fibrotic remodelling of viable segments, accentuate cardiomyocyte apoptosis and exert arrhythmogenic actions. Excessive, prolonged and dysregulated inflammation has been implicated in the pathogenesis of complications and may be involved in the development of heart failure following infarction. Studies in animal models of myocardial infarction (MI) have suggested the effectiveness of pharmacological interventions targeting the inflammatory response. This article provides a brief overview of the cell biology of the post-infarction inflammatory response and discusses the use of pharmacological interventions targeting inflammation following infarction. Therapy with broad anti-inflammatory and immunomodulatory agents may also inhibit important repair pathways, thus exerting detrimental actions in patients with MI. Extensive experimental evidence suggests that targeting specific inflammatory signals, such as the complement cascade, chemokines, cytokines, proteases, selectins and leukocyte integrins, may hold promise. However, clinical translation has proved challenging. Targeting IL-1 may benefit patients with exaggerated post-MI inflammatory responses following infarction, not only by attenuating adverse remodelling but also by stabilizing the atherosclerotic plaque and by inhibiting arrhythmia generation. Identification of the therapeutic window for specific interventions and pathophysiological stratification of MI patients using inflammatory biomarkers and imaging strategies are critical for optimal therapeutic design.

Hypothalamic-Pituitary-Adrenal Axis Modulation of Glucocorticoids in the Cardiovascular System

The collective of endocrine organs acting in homeostatic regulation—known as the hypothalamic-pituitary-adrenal (HPA) axis—comprises an integration of the central nervous system as well as peripheral tissues. These organs respond to imminent or perceived threats that elicit a stress response, primarily culminating in the release of glucocorticoids into the systemic circulation by the adrenal glands. Although the secretion of glucocorticoids serves to protect and maintain homeostasis in the typical operation at baseline levels, inadequate regulation can lead to physiologic and psychologic pathologies. The cardiovascular system is especially susceptible to prolonged dysregulation of the HPA axis and glucocorticoid production. There is debate about whether cardiovascular health risks arise from the direct detrimental effects of stress axis activation or whether pathologies develop secondary to the accompanying metabolic strain of excess glucocorticoids. In this review, we will explore the emerging research that indicates stress does have direct effects on the cardiovascular system via the HPA axis activation, with emphasis on the latest research on the impact of glucocorticoids signaling in the vasculature and the heart.

Gender-specific impairment of in vitro sinoatrial node chronotropic responses and of myocardial ischemia tolerance in rats exposed prenatally to betamethasone

Excessive fetal glucocorticoid exposure has been linked to increased susceptibility to hypertension and cardiac diseases in the adult life, a process called fetal programming. The cardiac contribution to the hypertensive phenotype of glucocorticoid-programmed progeny is less known, therefore, we investigated in vitro cardiac functional parameters from rats exposed in utero to betamethasone. Pregnant Wistar rats received vehicle (VEH) or betamethasone (BET, 0.1mg/kg, i.m.) at gestational days 12, 13, 18 and 19. Male and female offspring were killed at post-natal day 30 and the right atrium (RA) was isolated to in vitro evaluation of drug-induced chronotropic responses. Additionally, whole hearts were retrograde-perfused in a Langendorff apparatus and infarct size in response to in vitro ischemia/reperfusion (I/R) protocol was evaluated. Male and female progeny from BET-exposed pregnant rats had reduced birth weight, a hallmark of fetal programming. Male BET-progeny had increased basal RA rate, impaired chronotropic responses to noradrenaline and adenosine, and increased myocardial damage to I/R. Though a 12-fold reduction in the negative chronotropic responses to adenosine, the effects of non-metabolisable adenosine receptor agonists 5'-(N-ethylcarboxamido)adenosine or 2-Chloro-adenosine were not different between VEH- and BET-exposed male rats. BET-exposed female offspring presented no cardiac dysfunction. Prenatal BET exposure engenders male-specific impairment of sinoatrial node function and on myocardial ischemia tolerance resulting, at least in part, from an increased adenosine metabolism in the heart. In light of the importance of adenosine in the cardiac physiology our results suggest a link between reduced adenosinergic signaling and the cardiac dysfunctions observed in glucocorticoid-induced fetal programming.

Effect of Glucocorticoids on Ultrastructure of Myocardial Muscle in the Course of Experimentally Induced Acute Myocardial Ischemia

The search for effective methods of myocardial cytoprotection against ischemia is the most significant issue in modern cardiology and cardiac surgery. Glucocorticoids are deemed very strong modulators of inflammatory response and thus can potentially protect heart muscle from postreperfusion injury and myocardial ischemia during cardiac surgery. Ultrastructural examination of the left ventricle heart samples revealed that the intravenous application of dexamethasone and hydrocortisone proved to exert cytoprotective effect on cardiomyocytes during experimentally induced acute ischemia in rats.

MicroRNA-210 suppresses glucocorticoid receptor expression in response to hypoxia in fetal rat cardiomyocytes

Hypoxia is a common intrauterine stressor, often resulting in intrauterine growth restriction and increased risk for cardiovascular disease later in life. The aim of this work was to test the hypothesis that microRNA-210 (miR-210) mediates the detrimental suppression of glucocorticoid receptor (GR) in response to hypoxia in fetal rat cardiomyocytes. Cardiomyocytes isolated from gestational day 21 Sprague Dawley fetal rats showed increased miR-210 levels and reduced GR abundance after exposure to ex vivo hypoxia (1% O2). In regard to mechanisms, the different contributions of hypoxia response elements (HREs) motifs in the regulation of miR-210 promoter activity and the miR-210-mediated repression of GR expression were determined in rat embryonic heart-derived myogenic cell line H9c2. Moreover, using a cell culture-based model of hypoxia-reoxygenation injury, we assessed the cytotoxic effects of GR suppression under hypoxic conditions. The results showed that hypoxia induced HIF-1α-dependent miR-210 production, as well as miR-210-mediated GR suppression, in cardiomyocytes. Furthermore, inhibition or knockdown of GR exacerbated cell death in response to hypoxia-reoxygenation injury. Altogether, the present study demonstrates that the HIF-1α-dependent miR-210-mediated suppression of GR in fetal rat cardiomyocytes increases cell death in response to hypoxia, providing novel evidence for a possible mechanistic link between fetal hypoxia and programming of ischemic-sensitive phenotype in the developing heart.

Differential Regulation of Bcl-xL Gene Expression by Corticosterone, Progesterone, and Retinoic Acid

Corticosterone (CT), progesterone (PG), and retinoic acid (RA) are capable of inhibiting Doxorubicin (Dox) from inducing apoptosis in rat cardiomyocytes. Mechanistically, CT, PG, and RA induce increases of Bcl-xL protein and mRNA, and activate a 3.2 kb bcl-x gene promoter. CT and RA, but not PG, induced the activity of a 0.9 kb bcl-x promoter, containing sequences for AP-1 and NF-kB binding. RA, but not CT or PG, induced NF-kB activation. CT, but not PG or RA, induced AP-1 activation, and induction of the 0.9 kb bcl-x reporter by CT was inhibited by dominant negative c-Jun TAM-67 or removal of AP-1 binding site. Therefore, although CT, PG, and RA all induce Bcl-xL mRNA and protein, three independent mechanisms are in operation: while CT induces Bcl-xL via AP-1 transcription factor, and RA induces NF-kB activation and bcl-x promoter activity, PG induces Bcl-xL via a mechanism independent of NF-kB or AP-1.

Glucocorticoid signaling in the heart: A cardiomyocyte perspective

Heart failure is one of the leading causes of death in the Western world. Glucocorticoids are primary stress hormones that regulate a vast array of biological processes, and synthetic derivatives of these steroids have been mainstays in the clinic for the last half century. Abnormal levels of glucocorticoids are known to negatively impact the cardiovascular system; however, surprisingly little is known about the direct role of glucocorticoid signaling in the heart. The actions of glucocorticoids are mediated classically by the glucocorticoid receptor (GR). In certain cells, such as cardiomyocytes, glucocorticoid occupancy and activation of the mineralocorticoid receptor (MR) may also contribute to the observed response. Recently, there has been a surge of reports investigating the in vivo function of glucocorticoid signaling in the heart using transgenic mice that specifically target GR or MR in cardiomyocytes. Results from these studies suggest that GR signaling in cardiomyocytes is critical for the normal development and function of the heart. In contrast, MR signaling in cardiomyocytes participates in the development and progression of cardiac disease. In the following review, we discuss these genetic mouse models and the new insights they are providing into the direct role cardiomyocyte glucocorticoid signaling plays in heart physiology and pathophysiology. This article is part of a Special Issue entitled 'Steroid Perspectives'.

Correlation of serum- and glucocorticoid-regulated kinase 1 expression with ischemia-reperfusion injury after heart transplantation

IRI of a transplanted heart may result in serious early and late disadvantageous effects such as increased allograft immunogenicity, primary graft dysfunction, and initiation of fibroproliferative cascades that compromise the survival of the recipient. Sgk-1 has recently been linked to cell growth and survival. It has been reported that through a renal transplantation model, Dexa increases Sgk-1 expression and therefore protects from renal IRI. In our current study, we aim to assess the expression of Sgk-1 and its protective effects on cardiomyocyte IRI after heart transplantation. Heart allograft model was performed from Wistar into Lewis, and isograft model was from Lewis into Lewis. Grafts were then harvested at one, six, 12, or 24 h post-transplantation for Sgk-1 expression analyses. In some groups, part donors were treated with Dexa 2 h prior at doses of 0.05, 0.5 and 2 mg/BWkg, respectively. Sgk-1 expression was markedly increased in grafted heart 6-12 h post-transplantation in both the allogenic and isogenic models. Immunostaining experiments confirmed that Sgk-1 was expressed in cardiomyocytes rather than infiltrated immune cells. Furthermore, Dexa treatment significantly increased Sgk-1 expression and the donor cardiomyocyte injury was greatly minimized by Dexa treatment. These results suggest that induction of Sgk-1 might explain some of the beneficial impact of corticosteroids in IRI and hence might have therapeutic implications.

A combination of methylprednisolone and quercetin is effective for the treatment of cardiac contusion following blunt chest trauma in rats

Cardiac contusion is a potentially fatal complication of blunt chest trauma. The effects of a combination of quercetin and methylprednisolone against trauma-induced cardiac contusion were studied. Thirty-five female Sprague-Dawley rats were divided into five groups (n=7) as follows: sham, cardiac contusion with no therapy, treated with methylprednisolone (30 mg/kg on the first day, and 3 mg/kg on the following days), treated with quercetin (50 mg·kg⁻¹·day⁻¹), and treated with a combination of methylprednisolone and quercetin. Serum troponin I (Tn-I) and tumor necrosis factor-alpha (TNF-α) levels and cardiac histopathological findings were evaluated. Tn-I and TNF-α levels were elevated after contusion (P=0.001 and P=0.001). Seven days later, Tn-I and TNF-α levels decreased in the rats treated with methylprednisolone, quercetin, and the combination of methylprednisolone and quercetin compared to the rats without therapy, but a statistical significance was found only with the combination therapy (P=0.001 and P=0.011, respectively). Histopathological degeneration and necrosis scores were statistically lower in the methylprednisolone and quercetin combination group compared to the group treated only with methylprednisolone (P=0.017 and P=0.007, respectively). However, only degeneration scores were lower in the combination therapy group compared to the group treated only with quercetin (P=0.017). Inducible nitric oxide synthase positivity scores were decreased in all treatment groups compared to the untreated groups (P=0.097, P=0.026, and P=0.004, respectively). We conclude that a combination of quercetin and methylprednisolone can be used for the specific treatment of cardiac contusion.

Glucocorticoid induced leucine zipper inhibits apoptosis of cardiomyocytes by doxorubicin

Doxorubicin (Dox) is an indispensable chemotherapeutic agent for the treatment of various forms of neoplasia such as lung, breast, ovarian, and bladder cancers. Cardiotoxicity is a major concern for patients receiving Dox therapy. Previous work from our laboratory indicated that glucocorticoids (GCs) alleviate Dox-induced apoptosis in cardiomyocytes. Here we have found glucocorticoid-induced leucine zipper (GILZ) to be a mediator of GC-induced cytoprotection. GILZ was found to be induced in cardiomyocytes by GC treatment. Knocking down of GILZ using siRNA resulted in cancelation of GC-induced cytoprotection against apoptosis by Dox treatment. Overexpressing GILZ by transfection was able to protect cells from apoptosis induced by Dox as measured by caspase activation, Annexin V binding and morphologic changes. Western blot analyses indicate that GILZ overexpression prevented cytochrome c release from mitochondria and cleavage of caspase-3. When bcl-2 family proteins were examined, we found that GILZ overexpression causes induction of the pro-survival protein Bcl-xL. Since siRNA against Bcl-xL reverses GC induced cytoprotection, Bcl-xL induction represents an important event in GILZ-induced cytoprotection. Our data suggest that GILZ functions as a cytoprotective gene in cardiomyocytes.

Expression of glucocorticoid-induced leucine zipper (GILZ) in cardiomyocytes

Glucocorticoids (GCs) are frequently prescribed pharmacological agents most notably for their immunosuppressive effects. Endogenous GCs mediate biological processes such as energy metabolism and tissue development. At the cellular level, GCs bind to the glucocorticoid receptor (GR), a cytosolic protein that translocates to the nuclei and functions to alter transcription upon ligand binding. Among a long list of genes activated by GCs is the glucocorticoid-induced leucine zipper (GILZ). GC-induced GILZ expression has been well established in lymphocytes and mediates GC-induced apoptosis. Unlike lymphocytes, cardiomyocytes respond to GCs by gaining resistance against apoptosis. We determined GILZ expression in cardiomyocytes in vivo and in vitro. Expression of GILZ in mouse hearts as a result of GC administration was confirmed by Western blot analyses. GCs induced dose- and time-dependent elevation of GILZ expression in primary cultured rat cardiomyocytes, with dexamethasone (Dex) as low as 0.1 μM being effective. Time course analysis indicated that GILZ protein levels increased at 8 h and peaked at 48 h after exposure to 1 μM Dex. H9c2(2-1) cell line showed a similar response of GILZ induction by Dex as primary cultured rat cardiomyocytes, providing a convenient model for studying the biological significance of GILZ expression. With corticosterone (CT), an endogenous form of corticosteroids in rodents, 0.1-2.5 μM was found to induce GILZ in H9c2(2-1) cells. Time course analysis with 1 μM CT indicated induction of GILZ at 6 h with peak expression at 18 h. Inhibition of the GR by mifepristone led to blunting of GILZ induction by GCs. Our data demonstrate GILZ induction in cardiomyocytes both in vivo and in vitro by GCs, pointing to H9c2(2-1) cells as a valid model for studying the biological function of GILZ in cardiomyocytes.

Zebrafish Expression Ontology of Gene Sets (ZEOGS): a tool to analyze enrichment of zebrafish anatomical terms in large gene sets

The zebrafish (Danio rerio) is an established model organism for developmental and biomedical research. It is frequently used for high-throughput functional genomics experiments, such as genome-wide gene expression measurements, to systematically analyze molecular mechanisms. However, the use of whole embryos or larvae in such experiments leads to a loss of the spatial information. To address this problem, we have developed a tool called Zebrafish Expression Ontology of Gene Sets (ZEOGS) to assess the enrichment of anatomical terms in large gene sets. ZEOGS uses gene expression pattern data from several sources: first, in situ hybridization experiments from the Zebrafish Model Organism Database (ZFIN); second, it uses the Zebrafish Anatomical Ontology, a controlled vocabulary that describes connected anatomical structures; and third, the available connections between expression patterns and anatomical terms contained in ZFIN. Upon input of a gene set, ZEOGS determines which anatomical structures are overrepresented in the input gene set. ZEOGS allows one for the first time to look at groups of genes and to describe them in terms of shared anatomical structures. To establish ZEOGS, we first tested it on random gene selections and on two public microarray datasets with known tissue-specific gene expression changes. These tests showed that ZEOGS could reliably identify the tissues affected, whereas only very few enriched terms to none were found in the random gene sets. Next we applied ZEOGS to microarray datasets of 24 and 72 h postfertilization zebrafish embryos treated with beclomethasone, a potent glucocorticoid. This analysis resulted in the identification of several anatomical terms related to glucocorticoid-responsive tissues, some of which were stage-specific. Our studies highlight the ability of ZEOGS to extract spatial information from datasets derived from whole embryos, indicating that ZEOGS could be a useful tool to automatically analyze gene expression pattern features of any large zebrafish gene set.

Glucocorticoids and their receptors: insights into specific roles in mitochondria

Glucocorticoids (GCs) affect most physiological systems and are the most frequently used drugs for multiple disorders and organ transplantation. GC functions depend on a balance between circulating GC and cytoplasmic glucocorticoid receptor II (GR). Mitochondria individually enclose circular, double-stranded DNA that is expressed and replicated in response to nuclear-encoded factors imported from the cytoplasm. Fine-tuning and response to cellular demands should be coordinately regulated by the nucleus and mitochondria; thus mitochondrial-nuclear interaction is vital to optimal mitochondrial function. Elucidation of the direct and indirect effects of steroids, including GCs, on mitochondria is an important and emerging field of research. Mitochondria may also be under GC control because GRs are present in mitochondria, and glucocorticoid response elements (GREs) reside in the mitochondrial genome. Therefore, mitochondrial gene expression can be regulated by GCs via at least two different mechanisms: direct action on mitochondrial DNA and oxidative phosphorylation (OXPHOS) genes, or by an indirect effect through interaction with nuclear genes. In this review, we outline possible mechanisms of regulation of mitochondrial genes in response to GCs in view of translocation of the GR into mitochondria and the possible regulation of OXPHOS genes by GREs in the mitochondrial genome.

Tissue-specific actions of glucocorticoids on apoptosis: a double-edged sword

First described for their metabolic and immunosuppressive effects, glucocorticoids are widely prescribed in clinical settings of inflammation. However, glucocorticoids are also potent inducers of apoptosis in many cell types and tissues. This review will focus on the established mechanisms of glucocorticoid-induced apoptosis and outline what is known about the apoptotic response in cells and tissues of the body after exposure to glucocorticoids. Glucocorticoid-induced apoptosis affects the skeletal system, muscular system, circulatory system, nervous system, endocrine system, reproductive system, and the immune system. Interestingly, several cell types have an anti-apoptotic response to glucocorticoids that is cytoprotective. Lastly, we will discuss the pro- and anti-apoptotic effects of glucocorticoids in cancers and their clinical implications.

Dual role for glucocorticoids in cardiomyocyte hypertrophy and apoptosis

Glucocorticoids and their synthetic derivatives are known to alter cardiac function in vivo; however, the nature of these effects and whether glucocorticoids act directly on cardiomyocytes are poorly understood. To explore the role of glucocorticoid signaling in the heart, we used rat embryonic H9C2 cardiomyocytes and primary cardiomyocytes as model systems. Dexamethasone (100 nm) treatment of cardiomyocytes caused a significant increase in cell size and up-regulated the expression of cardiac hypertrophic markers, including atrial natriuretic factor, β-myosin heavy chain, and skeletal muscle α-actin. In contrast, serum deprivation and TNFα exposure triggered cardiomyocyte apoptosis, and these apoptotic effects were inhibited by dexamethasone. Both the hypertrophic and anti-apoptotic actions of glucocorticoids were abolished by the glucocorticoid receptor (GR) antagonist RU486 and by short hairpin RNA-mediated GR depletion. Blocking the activity of the mineralocorticoid receptor had no effect on these glucocorticoid-dependent cardiomyocyte responses. Aldosterone (1 μm) activation of GR also promoted cardiomyocyte hypertrophy and cell survival. To elucidate the mechanism of the dual glucocorticoid actions, a genome-wide microarray was performed on H9C2 cardiomyocytes treated with vehicle or dexamethasone in the absence or presence of serum. Serum dramatically influenced the transcriptome regulated by GR, revealing potential glucocorticoid signaling mediators in both cardiomyocyte hypertrophy and apoptosis. These studies reveal a direct and dynamic role for glucocorticoids and GR signaling in the modulation of cardiomyocyte function.

Glycogen synthase kinase-3β is involved in ligand-dependent activation of transcription and cellular localization of the glucocorticoid receptor

Glucocorticoids (GC) induce cell cycle arrest and apoptosis in different cell types and therefore are widely used to treat a variety of diseases including autoimmune disorders and cancer. This effect is mediated by the GC receptor (GR), a ligand-activated transcription factor that translocates into the nucleus where it modulates transcription of target genes in a promoter-specific manner. Glycogen synthase kinase-3 (GSK3) regulates GR response by genomic and nongenomic mechanisms, although the specific role of each isoform is not well defined. We used GSK3 pharmacological inhibitors and isoform-specific small interfering RNA to evaluate the role of GSK3 in the genomic regulation induced by GC. GSK3 inhibition resulted in the reduction of GC-induced mRNA expression of GC-induced genes such as BIM, HIAP1, and GILZ. Knockdown of GSK3β but not GSK3α reduced endogenous GILZ induction in response to dexamethasone and GR-dependent reporter gene activity. Chromatin immunoprecipitation experiments revealed that GSK3 inhibition impaired the dexamethasone-mediated binding of GR and RNA polymerase II to endogenous GILZ promoter. These results indicate that GSK3β is important for GR transactivation activity and that GSK3β inhibition suppresses GC-stimulated gene expression. Furthermore, we show that genomic regulation by the GR is independent of known GSK3β phosphorylation sites. We propose that GC-dependent transcriptional activation requires functional GSK3β signaling and that altered GSK3β activity influences cell response to GC.