Dexamethasone-induced myocardial hypertrophy in neonatal rats

Prenatal hormone stress triggers embryonic cardiac hypertrophy outcome by ubiquitin-dependent degradation of mitochondrial mitofusin 2

Prenatal stress has been extensively documented as a contributing factor to adverse cardiac development and function in fetuses and infants. The release of glucocorticoids (GCs), identified as a significant stressor, may be a potential factor inducing cardiac hypertrophy. However, the underlying mechanism remains largely unknown. Herein, we discovered that corticosterone (CORT) overload induced cardiac hypertrophy in embryonic chicks and fetal mice in vivo, as well as enlarged cardiomyocytes in vitro. The impaired mitochondria dynamics were observed in CORT-exposed cardiomyocytes, accompanied by dysfunction in oxidative phosphorylation and ATP production. This phenomenon was found to be linked to decreased mitochondrial fusion protein mitofusin 2 (MFN2). Subsequently, we found that CORT facilitated the ubiquitin-proteasome-system-dependent degradation of MFN2 with an enhanced binding of appoptosin to MFN2, serving as the underlying cause. Collectively, our findings provide a comprehensive understanding of the mechanisms by which exposure to stress hormones induces cardiac hypertrophy in fetuses.

Klf9 plays a critical role in GR -dependent metabolic adaptations in cardiomyocytes

Glucocorticoids through activation of the Glucocorticoid receptor (GR) play an essential role in cellular homeostasis during physiological variations and in response to stress. Our genomic GR binding and transcriptome data from Dexamethasone (Dex) treated cardiomyocytes showed an early differential regulation of mostly transcription factors, followed by sequential change in genes involved in downstream functional pathways. We examined the role of Krüppel-like factor 9 (Klf9), an early direct target of GR in cardiomyocytes. Klf9-ChIPseq identified 2150 genes that showed an increase in Klf9 binding in response to Dex. Transcriptome analysis of Dex treated cardiomyocytes with or without knockdown of Klf9 revealed differential regulation of 1777 genes, of which a reversal in expression is seen in 1640 genes with knockdown of Klf9 compared to Dex. Conversely, only 137 (∼8%) genes show further dysregulation in expression with siKLf9, as seen with Dex treated cardiomyocytes. Functional annotation identified genes of metabolic pathways on the top of differentially expressed genes, including those involved in glycolysis and oxidative phosphorylation. Knockdown of Klf9 in cardiomyocytes inhibited Dex induced increase in glycolytic function and mitochondrial spare respiratory capacity, as measured by glycolysis and mito stress tests, respectively. Thus, we conclude that cyclic, diurnal GR activation, through Klf9 -dependent feedforward signaling plays a central role in maintaining cellular homeostasis through metabolic adaptations in cardiomyocytes.

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.

Dose-related cardiac outcomes in response to postnatal dexamethasone treatment in premature lambs

BACKGROUND

Postnatal corticosteroids are used in the critical care of preterm infants for the prevention and treatment of bronchopulmonary dysplasia. We aimed to investigate the effects of early postnatal dexamethasone therapy and dose on cardiac maturation and morphology in preterm lambs.

METHODS

Lambs were delivered prematurely at ~128 days of gestational age and managed postnatally according to best clinical practice. Preterm lambs were administered dexamethasone daily at either a low-dose (n = 9) or a high-dose (n = 7), or were naïve to steroid treatment and administered saline (n = 9), over a 7-day time-course. Hearts were studied at postnatal Day 7 for gene expression and assessment of myocardial structure.

RESULTS

High-dose dexamethasone treatment in the early postnatal period led to marked differences in cardiac gene expression, altered cardiomyocyte maturation and reduced cardiomyocyte endowment in the right ventricle, as well as increased inflammatory infiltrates into the left ventricle. Low-dose exposure had minimal effects on the preterm heart.

CONCLUSION

Neonatal dexamethasone treatment led to adverse effects in the preterm heart in a dose-dependent manner within the first week of life. The observed cardiac changes associated with high-dose postnatal dexamethasone treatment may influence postnatal growth and remodeling of the preterm heart and subsequent long-term cardiac function.

Immunological and hemato-biochemical effects on catfish (Clarias gariepinus) exposed to dexamethasone

Dexamethasone (glucocorticoid) was recently shown to be a life-saving drug for the treatment of SARS-CoV-2 disease. Water and sediments can be contaminated by sewage treatment plants when this product is widely used. Accordingly, we evaluated the effects of dexamethasone as pharmaceutical residue on Clarias gariepinus, following exposure and post-exposure recovery on blood biochemical, antioxidant, and cytokine markers. Three experimental groups were examined. Control, fish exposed to 0.3 mg/L of dexamethasone, and fish exposed to 3 mg/L of dexamethasone for 7 days, followed by a 15-days recovery period. Hematological indices, such as red blood cell number, hemoglobin (Hb), platelets, mean corpuscular hemoglobin concentration, and large lymphocytes, were significantly declined following the exposure to dexamethasone compared to control. In contrast, hematocrit (Ht), mean corpuscular volume, monocytes, small lymphocytes, and mean corpuscular hemoglobin increased significantly depending on the dose–concentration. Liver and kidney functions, other biochemical parameters (albumin and globulin), cortisol, and cytokine (IL-1β and IL-6) concentrations increased significantly after exposure to dexamethasone compared to control. Antioxidants and acetylcholinesterase enzymes were significantly decreased in catfish treated with dexamethasone cumulatively with doses. After a recovery period, blood biochemical, antioxidant, and cytokine markers were still elevated compared with the control group. In conclusion, dexamethasone at concentrations present in water bodies causes deleterious effects on blood biomarkers, biochemical, and antioxidant as well as immune upregulation in catfish until after depuration period.

Effect of Preterm Birth on Cardiac and Cardiomyocyte Growth and the Consequences of Antenatal and Postnatal Glucocorticoid Treatment

Preterm birth coincides with a key developmental window of cardiac growth and maturation, and thus has the potential to influence long-term cardiac function. Individuals born preterm have structural cardiac remodelling and altered cardiac growth and function by early adulthood. The evidence linking preterm birth and cardiovascular disease in later life is mounting. Advances in the perinatal care of preterm infants, such as glucocorticoid therapy, have improved survival rates, but at what cost? This review highlights the short-term and long-term impact of preterm birth on the structure and function of the heart and focuses on the impact of antenatal and postnatal glucocorticoid treatment on the immature preterm heart.

Glucocorticoid Receptor-Binding and Transcriptome Signature in Cardiomyocytes

Background

An increase in serum cortisol has been identified as a risk factor for cardiac failure, which highlights the impact of glucocorticoid signaling in cardiomyocytes and its influence in the progression of failure. Dexamethasone, a synthetic glucocorticoid, is sufficient for induction of cardiomyocyte hypertrophy, but little is known of the glucocorticoid receptor (GR) genome‐binding and ‐dependent transcriptional changes that mediate this phenotype.

Methods and Results

In this study using high‐resolution sequencing, we identified genomic targets of GR and associated change in the transcriptome after 1 and 24 hours of dexamethasone treatment. We showed that GR associates with 6482 genes in the cardiac genome, with differential regulation of 738 genes. Interestingly, alignment of the chromatin immunoprecipitation and RNA sequencing data show that, after 1 hour, 69% of differentially regulated genes are associated with GR and identify as regulators of RNA pol II–dependent transcription. Conversely, after 24 hours only 45% of regulated genes are associated with GR and involved in dilated and hypertrophic cardiomyopathies as well as other growth‐related pathways. In addition, our data also reveal that a majority of genes (76.42%) associated with GR show incremental changes in transcript abundance and are genes involved in basic cellular processes that might be regulated by the dynamics of promoter‐paused RNA pol II, as seen in hearts undergoing hypertrophy. In vivo administration of dexamethasone resulted in similar changes in the cardiac transcriptome, as seen in isolated cardiomyocytes.

Conclusions

Our data reveal genome‐wide GR binding sites in cardiomyocytes, identify novel targets and GR‐dependent change in the transcriptome that induces and contributes to cardiomyocyte hypertrophy.

Glucocorticoid Signaling and the Aging Heart

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

Glucocorticoid exposure causes disrupted glucoregulation, cardiac inflammation and elevated dipeptidyl peptidase-4 activity independent of glycogen synthase kinase-3 in female rats

Objective: We tested the hypothesis that glucocorticoid (GC) exposure in female rats would lead to glucose dysregulation and elevated cardiac inflammatory biomarkers, which are dipeptidyl peptidase-4 (DPP-4)- and glycogen synthase kinase-3 (GSK-3)-dependent. Methods: Female Wistar rats received vehicle (control; n = 6) or GC (dexamethasone; n = 6; 0.2 mg/kg; p.o.) for six days. Insulin resistance was determined by HOMA-IR. DPP-4 activity was determined by fluorescence method, whereas vascular cell adhesion molecule-1 (VCAM-1), uric acid, malondialdehyde (MDA), lactate dehydrogenase (LDH) and nitric oxide (NO) from plasma and cardiac homogenate were estimated as cardiac pro-inflammatory biomarkers. Results: Results showed that GC exposure resulted in glucose dysregulation and increased plasma and cardiac pro-inflammatory markers which are associated with elevated DPP-4 activity but reduced GSK-3. Conclusions: The present results demonstrate that GC exposure would cause glucose dysregulation, increased DPP-4 activity and cardiac inflammation that is independent of GSK-3.

Hormone treatments in congestive heart failure

The common ultimate pathological feature for all cardiovascular diseases, congestive heart failure (CHF), is now considered as one of the main public health burdens that is associated with grave implications. Neurohormonal systems play a critical role in cardiovascular homeostasis, pathophysiology, and cardiovascular diseases. Hormone treatments such as the newly invented dual-acting drug valsartan/sacubitril are promising candidates for CHF, in addition to the conventional medications encompassing beta receptor blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and mineralocorticoid receptor antagonists. Clinical trials also indicate that in CHF patients with low insulin-like growth factor-1 or low thyroid hormone levels, supplemental treatment with growth hormone or thyroid hormone seems to be cardioprotective; and in CHF patients with volume overload the vasopressin antagonists can relieve the symptoms superior to loop diuretics. Furthermore, a combination of selective glucocorticoid receptor agonist and mineralocorticoid receptor antagonist may be used in patients with diuretic resistance. Finally, the potential cardiovascular efficacy and safety of incretin-based therapies, testosterone or estrogen supplementation needs to be prudently evaluated in large-scale clinical studies. In this review, we briefly discuss the therapeutic effects of several key hormones in CHF.

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'.

Dexamethasone Treatment of Newborn Rats Decreases Cardiomyocyte Endowment in the Developing Heart through Epigenetic Modifications

The potential adverse effect of synthetic glucocorticoid, dexamethasone therapy on the developing heart remains unknown. The present study investigated the effects of dexamethasone on cardiomyocyte proliferation and binucleation in the developing heart of newborn rats and evaluated DNA methylation as a potential mechanism. Dexamethasone was administered intraperitoneally in a three day tapered dose on postnatal day 1 (P1), 2 and 3 to rat pups in the absence or presence of a glucocorticoid receptor antagonist Ru486, given 30 minutes prior to dexamethasone. Cardiomyocytes from P4, P7 or P14 animals were analyzed for proliferation, binucleation and cell number. Dexamethasone treatment significantly increased the percentage of binucleated cardiomyocytes in the hearts of P4 pups, decreased myocyte proliferation in P4 and P7 pups, reduced cardiomyocyte number and increased the heart to body weight ratio in P14 pups. Ru486 abrogated the effects of dexamethasone. In addition, 5-aza-2'-deoxycytidine (5-AZA) blocked the effects of dexamethasone on binucleation in P4 animals and proliferation at P7, leading to recovered cardiomyocyte number in P14 hearts. 5-AZA alone promoted cardiomyocyte proliferation at P7 and resulted in a higher number of cardiomyocytes in P14 hearts. Dexamethasone significantly decreased cyclin D2, but not p27 expression in P4 hearts. 5-AZA inhibited global DNA methylation and blocked dexamethasone-mediated down-regulation of cyclin D2 in the heart of P4 pups. The findings suggest that dexamethasone acting on glucocorticoid receptors inhibits proliferation and stimulates premature terminal differentiation of cardiomyocytes in the developing heart via increased DNA methylation in a gene specific manner.

Corticosteroids increase intracellular free sodium ion concentration via glucocorticoid receptor pathway in cultured neonatal rat cardiomyocytes

Background

Glucocorticoids as well as mineralocorticoid have been shown to play essential roles in the regulation of electrical and mechanical activities in cardiomyocytes. Excess of these hormones is an independent risk factor for cardiovascular disease. Intracellular sodium ([Na⁺]_i) kinetics are involved in cardiac diseases, including ischemia, heart failure and hypertrophy. However, intrinsic mediators that regulate [Na⁺]_i in cardiomyocytes have not been widely discussed. Moreover, the quantitative estimation of altered [Na⁺]_i in cultured cardiomyocytes and the association between the level of [Na⁺]_i and the severity of pathological conditions, such as hypertrophy, have not been precisely reported.

Methods and results

We herein demonstrate the quantitative estimation of [Na⁺]_i in cultured neonatal rat cardiomyocytes following 24 h of treatment with corticosterone, aldosterone and dexamethasone. The physiological concentration of glucocorticoids increased [Na⁺]_i up to approximately 2.5 mM (an almost 1.5-fold increase compared to the control) in a dose-dependent manner; this effect was blocked by a glucocorticoid receptor (GR) antagonist but not a mineralocorticoid receptor antagonist. Furthermore, glucocorticoids induced cardiac hypertrophy, and the hypertrophic gene expression was positively and significantly correlated with the level of [Na⁺]_i. Dexamethasone induced the upregulation of Na⁺/Ca^{2 +} exchanger 1 at the mRNA and protein levels.

Conclusions

The physiological concentration of glucocorticoids increases [Na⁺]_i via GR. The dexamethasone-induced upregulation of NCX1 is partly involved in the glucocorticoid-induced alteration of [Na⁺]_i in cardiomyocytes. These results provide new insight into the mechanisms by which glucocorticoid excess within a physiological concentration contributes to the development of cardiac pathology.

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.

Glucocorticoid signaling in cardiac disease

As major mediators of stress regulation, glucocorticoids have an essential role in maintaining cardiovascular homeostasis under both physiological and pathological conditions. The release of glucocorticoids into the peripheral circulation is adjusted by the hypothalamic-pituitary-adrenal axis in response to various pathological challenges such as sepsis, starvation, and psychological stress. Clinically, dysregulation of the glucocorticoid-mediated signaling as a result of either excess ligand or receptor hypersensitivity is connected with the progression of unfavorable cardiovascular events such as cardiac hypertrophy, atherosclerosis, and coronary artery disease. The direct effects of glucocorticoids on cardiac tissues are mediated by two steroid receptors, the glucocorticoid receptor and mineralocorticoid receptor, which are both expressed by cardiomyocytes. Although each receptor has some shared responses to glucocorticoids, each receptor also has unique effects on cardiac functions. Elucidating the selective actions of each receptor is critical for determining the proper pharmaceutical targets in cardiovascular diseases.

Histopathological changes of the heart after neonatal dexamethasone treatment: studies in 4-, 8-, and 50-week-old rats

Dexamethasone (Dex), for prevention of chronic lung disease in preterm infants, showed potential negative long-term effects. Studies regarding long-term cardiovascular effects are lacking. We investigated possible histopathological myocardial changes after neonatal Dex in the young and adult rat heart. Rats were treated with Dex on d 1, 2, and 3 (0.5, 0.3, and 0.1 mg/kg) of life. Control-pups received saline. At 4, 8, and 50 wk after birth rats were killed and anatomic data collected. Heart tissue was stained with hematoxylin and eosin, Cadherin-periodic acid schiff, and sirius red for cardiomyocyte morphometry and collagen determination. Presence of macrophages and mast cells was analyzed. Cardiomyocyte length of the Dex-treated rats was increased in all three age groups, whereas ventricular weight was reduced. Cardiomyocyte volumes were increased at 50 wk indicating cellular hypertrophy. Collagen content gradually increased with age and was 62% higher in Dex rats at 50 wk. Macrophage focus score and mast cell count were also higher. Neonatal Dex affects normal heart growth resulting in cellular hypertrophy and increased collagen deposition in the adult rat heart. Because previous studies in rats showed premature death, suggesting cardiac failure, cardiovascular follow-up of preterm infants treated with glucocorticoids should be considered.

Ligand-based gene expression profiling reveals novel roles of glucocorticoid receptor in cardiac metabolism

Recent studies have documented various roles of adrenal corticosteroid signaling in cardiac physiology and pathophysiology. It is known that glucocorticoids and aldosterone are able to bind glucocorticoid receptor (GR) and mineralocorticoid receptor, and these ligand-receptor interactions are redundant. It, therefore, has been impossible to delineate how these nuclear receptors couple with corticosteroid ligands and differentially regulate gene expression for operation of their distinct functions in the heart. Here, to particularly define the role of GR in cardiac muscle cells, we applied a ligand-based approach involving the GR-specific agonist cortivazol (CVZ) and the GR antagonist RU-486 and performed microarray analysis using rat neonatal cardiomyocytes. We indicated that glucocorticoids appear to be a major determinant of GR-mediated gene expression when compared with aldosterone. Moreover, expression profiles of these genes highlighted numerous roles of glucocorticoids in various aspects of cardiac physiology. At first, we identified that glucocorticoids, via GR, induce mRNA and protein expression of a transcription factor Kruppel-like factor 15 and its downstream target genes, including branched-chain aminotransferase 2, a key enzyme for amino acid catabolism in the muscle. CVZ treatment or overexpression of KLF15 decreased cellular branched-chain amino acid concentrations and introduction of small-interfering RNA against KLF15 cancelled these CVZ actions in cardiomyocytes. Second, glucocorticoid-GR signaling promoted gene expression of the enzymes involved in the prostaglandin biosynthesis, including cyclooxygenase-2 and phospholipase A2 in cardiomyocytes. Together, we may conclude that GR signaling should have distinct roles for maintenance of cardiac function, for example, in amino acid catabolism and prostaglandin biosynthesis in the heart.

Long-term effects of neonatal hydrocortisone treatment for chronic lung disease on the developing brain and heart

Despite modern perinatal intensive care techniques, chronic lung disease remains a problem in preterm-born infants. The most commonly and almost exclusively prescribed drug to treat this disorder is dexamethasone. Corticosteroids improve short-term respiratory function; however, many side-effects have been reported and the adverse long-term effects of dexamethasone on neurodevelopment are particularly alarming. Hydrocortisone could be a suitable alternative for dexamethasone, if equally effective with fewer side-effects. This review evaluates the current literature on neonatal hydrocortisone treatment for chronic lung disease with regards to long-term neurodevelopmental outcome and cardiovascular effects. The neurodevelopmental studies do not show any adverse effects of hydrocortisone on neurocognitive and motor outcome, nor on incidence of brain abnormalities on magnetic resonance imaging or on long-lasting programming effects on the hypothalamus-pituitary-adrenal axis. At school age, cardiovascular stress response was the same in hydrocortisone-treated children compared with a reference group. Hydrocortisone seems a safe alternative to dexamethasone, but more double-blind randomised studies are needed.

Therapeutic manipulation of glucocorticoid metabolism in cardiovascular disease

The therapeutic potential for manipulation of glucocorticoid metabolism in cardiovascular disease was revolutionized by the recognition that access of glucocorticoids to their receptors is regulated in a tissue-specific manner by the isozymes of 11beta-hydroxysteroid dehydrogenase. Selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 have been shown recently to ameliorate cardiovascular risk factors and inhibit the development of atherosclerosis. This article addresses the possibility that inhibition of 11beta-hydroxsteroid dehydrogenase type 1 activity in cells of the cardiovascular system contributes to this beneficial action. The link between glucocorticoids and cardiovascular disease is complex as glucocorticoid excess is linked with increased cardiovascular events but glucocorticoid administration can reduce atherogenesis and restenosis in animal models. There is considerable evidence that glucocorticoids can interact directly with cells of the cardiovascular system to alter their function and structure and the inflammatory response to injury. These actions may be regulated by glucocorticoid and/or mineralocorticoid receptors but are also dependent on the 11beta-hydroxysteroid dehydrogenases which may be expressed in cardiac, vascular (endothelial, smooth muscle) and inflammatory (macrophages, neutrophils) cells. The activity of 11beta-hydroxysteroid dehydrogenases in these cells is dependent upon differentiation state, the action of pro-inflammaotory cytokines and the influence of endogenous inhibitors (oxysterols, bile acids). Further investigations are required to clarify the link between glucocorticoid excess and cardiovascular events and to determine the mechanism through which glucocorticoid treatment inhibits atherosclerosis/restenosis. This will provide greater insights into the potential benefit of selective 11beta-hydroxysteroid dehydrogenase inhibitors in treatment of cardiovascular disease.

Long-term cardiovascular effects of neonatal dexamethasone treatment: hemodynamic follow-up by left ventricular pressure-volume loops in rats

Dexamethasone is clinically applied in preterm infants to treat or prevent chronic lung disease. However, concern has emerged about adverse side effects. The cardiovascular short-term side effects of neonatal dexamethasone treatment are well documented, but long-term consequences are unknown. Previous studies showed suppressed mitosis during dexamethasone treatment, leading to reduced ventricular weight, depressed systolic function, and compensatory dilatation in prepubertal rats. In addition, recent data indicated a reduced life expectancy. Therefore, we investigated the long-term effects of neonatal dexamethasone treatment on cardiovascular function. Neonatal rats were treated with dexamethasone or received saline. Cardiac function was determined in 8-, 50-, and 80-wk-old animals, representing young adult, middle-aged, and elderly stages. A pressure-conductance catheter was introduced into the left ventricle to measure pressure-volume loops. Subsequently, the hearts were collected for histological examination. Our results showed reduced ventricular and body weights in dexamethasone-treated rats at 8 and 80 wk, but not at 50 wk. Cardiac output and diastolic function were unchanged, but systolic function was depressed at 50 and 80 wk, evidenced by reduced ejection fractions and rightward shifts of the end-systolic pressure-volume relationships. We concluded that previously demonstrated early adverse effects of neonatal dexamethasone treatment are transient but that reduced ventricular weight and systolic dysfunction become manifest again in elderly rats. Presumably, cellular hypertrophy initially compensates for the dexamethasone treatment-induced lower number of cardiomyocytes, but this mechanism falls short at a later stage, leading to systolic dysfunction. If applicable to humans, cardiac screening of a relatively large patient group to enable secondary prevention may be indicated.

Marked left ventricular hypertrophy mimicking hypertrophic cardiomyopathy associated with steroid therapy for congenital adrenal hyperplasia

We describe a child treated with high-dose steroid therapy for congenital adrenal hyperplasia who showed marked left ventricular hypertrophy mimicking hypertrophic cardiomyopathy associated with steroid therapy for congenital adrenal hyperplasia. Cardiomyopathy reversed completely when an appropriate steroid therapeutic regimen was established.

Reduced life expectancy in rats after neonatal dexamethasone treatment

The glucocorticoid dexamethasone (Dex) is widely used in preterm infants for the prevention of chronic lung disease. However, major concern has arisen about the long-term sequelae of this therapy. Here we report that neonatal treatment with dexamethasone significantly shortens the lifespan by 25% of male rats (28.6 +/- 1.1 to 21.3 +/- 0.8 mo) and by 18% of female rats (26.9 +/- 1.8 to 22.0 +/- 0.7 mo). Histopathological examination indicated end-stage cardiac and renal failure as the cause of premature death. Furthermore, Dex-treated rats showed symptoms of hypertension at young adult age, which worsened with increasing age. Thus, a brief period of glucocorticoid treatment during early life results in untimely death presumably due to cardiovascular and renal disease later in life. These serious, adverse long-term consequences call for prudence with glucocorticoid treatment of human preterm infants and careful follow-up of young adults with a history of neonatal glucocorticoid treatment.

Suppression of physiological cardiomyocyte proliferation in the rat pup after neonatal glucocorticosteroid treatment

BACKGROUND

Glucocorticosteroids (mostly dexamethasone) are widely used to prevent chronic lung disease in premature infants. Neonatal rats treated with dexamethasone have been shown to have reduced cardiac mass and cardiomyocyte hypertrophy, suggesting a lower number of cardiomyocytes at adult age, and a severely reduced life expectancy. In the present study we tested the hypothesis that a lower number of cardiomyocytes in later life is caused by a reduced cardiomyocyte proliferation and/or by early cell death (apoptosis).

METHODS AND RESULTS

Rat pups received dexamethasone or saline control on day 1, 2 and 3 and were sacrificed at day 0, 2, 4, 7 and 21. The cardiomyocytes of dexamethasone treated pups showed a reduced proliferation as indicated by a lower mitotic index and reduced number of Ki-67 positive cardiomyocytes on day 2 and 4 as compared to day 0 and day 7 and also as compared to the age-matched saline pups. On day 7 and day 21 the mitotic index was not different between groups. From day 2 onward up to day 21 dexamethasone treated pups showed a lower number of cardiomyocytes. The cardiomyocytes showed no signs (<<1%) of apoptosis (Caspase-3 and cleaved-PARP) in any group.

CONCLUSION

The temporary suppression of cardiomyocyte hyperplasia found in dexamethasone treated pups eventually leads to a reduced number and hypertrophy of cardiomyocytes during adult life.

Neonatal glucocorticosteroid treatment causes systolic dysfunction and compensatory dilation in early life: studies in 4-week-old prepubertal rats

Glucocorticosteroid treatment is widely used to prevent chronic lung disease in premature infants. Recent studies in adult rats, treated with dexamethasone in the neonatal period, report negative long-term effects on the heart and severely reduced life expectancy. We treated neonatal rats with dexamethasone and studied cardiac function after 4 wk (prepubertal age) to investigate whether the late effects as previously described are preceded by detectable alterations in cardiac function at a younger age. Male rat pups (n = 12) were injected intraperitoneally with dexamethasone on d 1, 2, and 3 (0.5, 0.3, and 0.1 mug/g) of life. Control pups (n = 10) received saline. At 4 wk the animals were anesthetized, and a pressure-conductance catheter was introduced into the left ventricle to measure pressure-volume loops. Cardiac function was measured and pressure-volume relations were determined to quantify intrinsic systolic and diastolic function. Subsequently, hearts were excised for histologic examination. Compared with saline-treated animals, dexamethasone-treated rats had a reduced ventricular weight (270 +/- 40 versus 371 +/- 23 mg, p < 0.001) and reduced systolic function (end-systolic elastance: 1.24 +/- 0.43 versus 2.50 +/- 1.39 mm Hg/muL, p = 0.028). Cardiac output was maintained and end-diastolic volume was increased (84 +/- 23 versus 59 +/- 19 microL, p = 0.012) indicating a state of compensatory dilatation. Heart rate, diastolic function, and systemic vascular resistance were unchanged. Neonatal dexamethasone treatment causes cardiac alterations that can be detected in the prepubertal period and that may precede severe cardiac dysfunction later in life. If our findings are confirmed in humans, this may have consequences for a large patient population and cardiac screening at young age may be indicated to enable secondary prevention.

Alterations in adult rat heart after neonatal dexamethasone therapy

Glucocorticoid treatment in preterm babies to prevent chronic lung disease causes myocardial hypertrophy and increased myocardial protein content. Although these changes are thought to be transient, there is evidence that dexamethasone (DEX) induces permanent myocardial abnormalities as well. We investigated whether a therapeutic course of neonatal DEX in rat pups produces anatomic and biochemical alterations in rat hearts during adult life. Twenty-four rat pups were treated with DEX on d 1, 2, and 3 (0.5, 0.3, and 0.1 micro g/g) of life, with doses proportional to those used in preterm babies. Twenty-four control pups were treated with saline. At d 7, wk 8, or wk 45 (n = 8 per group) rats were killed. The anatomic parameters measured were body weight (Bw, in grams), heart (myocardial) weight (Hw, in milligrams), and the Hw:Bw ratio. Myocardial total protein (Prot) and DNA content were determined, and the Prot:DNA ratio was calculated. Histopathology and morphometry were performed on 45-wk-old rat hearts. In DEX-treated rat pups, at d 7, Bw and Hw were lower and the Hw:Bw ratio was increased. DNA content was lower, Prot higher, and Prot:DNA ratio was increased. In 8-wk-old rats Bw, Hw, DNA content, Prot content or Prot:DNA ratio did not differ between groups, but the Prot:DNA ratio still tended to be higher in DEX-treated rats. In 45-wk-old rats Hw and Hw:Bw ratio were significantly lower and Prot:DNA ratio higher in DEX-treated rats. Histopathologic analysis showed larger cardiomyocyte volume, length, and width, indicating hypertrophy, and increased collagen, indicating early degeneration of individual myocytes. In conclusion, neonatal DEX treatment in rat pups causes a permanent decrease in heart weight, as well as hypertrophy and early degeneration of cardiomyocytes during adulthood.

Improving delivery and offspring viability of in vitro-produced and cloned sheep embryos

Recently developed, assisted reproductive technologies (e.g., in vitro embryo production and nuclear transfer) have encountered perinatal morbidity/mortality of the offspring produced, which are likely to hinder the application of these techniques. Consequently we have sought to develop a system of hormonal stimulation that will ensure the delivery of offspring more prepared for extrauterine life. Here we examine deliveries outcome in sheep carrying in vitro-produced and nuclear transfer (NT) embryos in comparison to artificially inseminated and naturally mated control ewes. All groups (excluding NT, which received one treatment) were subjected to one of two hormonal treatments for induction of delivery, whereas the third part of each group was left without any treatment. The first (commonly used for naturally mated ewes) dexamethasone treatment did not solve a majority of parturition disturbances, and actually the number of deliveries necessitating assistance was reduced (P < 0.05) by this treatment in the control group. On the other hand, combined estradiol plus betamethasone stimulation (E + B) solved a majority of complications regarding delivery performance such as lack of the preparation of the mammary gland, low myometrial contractility, insufficient cervical ripening, and impaired maternal behavior. Moreover, substantial reduction of neonatal mortality was observed following the combined treatment. In conclusion, the E + B induction of delivery overcame the majority of physiological and behavioral intrapartum failures of sheep foster mothers and increased the survival of offspring, and thus can be recommended as a safe method for inducing delivery in foster mothers carrying in vitro-generated embryos.

Cardiac adverse effects of early dexamethasone treatment in preterm infants: a randomized clinical trial

This study evaluates the effects of early administration of dexamethasone on left ventricle dimensions and their clinical significance in preterm infants. Fifty preterm infants with birth weight < or = 1250 g and gestational age < or = 30 weeks were randomly assigned after 72 hours of life to the dexamethasone group (n = 25) or to the control group (n = 25). The treated infants received dexamethasone intravenously from the 4th day of life for 7 days (0.5 mg/kg/day for the first 3 days, 0.25 mg/kg/day for the next 3 days, and 0.125 mg/kg/day for the 7th day). Serial echocardiographic measurements of end systolic interventricular septum thickness, end diastolic interventricular septum thickness, end systolic left ventricle posterior wall thickness, end diastolic left ventricle posterior wall thickness, left ventricle end diastolic diameter, and left ventricle end systolic diameter were taken before starting dexamethasone, on days 3 and 7 of treatment, 7 days after the interruption of treatment, and at the 28th day of life. Five infants of each group were excluded by the final analysis because of the lack of a complete cardiac evaluation, leaving 20 treated and 20 control infants. Infants receiving dexamethasone had a significantly larger increase in mean septal and left posterior wall thickness during the treatment and 7 days after the dexamethasone weaning. The mean left ventricle diameter of treated infants was significantly lower than that of control infants from the 7th day of treatment to the 28th day of life. Four neonates (20%) in the dexamethasone group developed left ventricular myocardial hypertrophy without left ventricle outflow tract obstruction, showing signs of decreased cardiac output and ischemic changes on ECG. The daily fluid intake was increased to 200 ml/kg to ensure an adequate preload volume, and the complete resolution of left ventricle hypertrophy was obtained within the 2nd to 3rd week after dexamethasone weaning. Preterm infants receiving an early (< 96 hours of life) short course of dexamethasone develop a left ventricular myocardial hypertrophy that can be symptomatic and clinically significant. Preterm infants included in future studies with the goal to find the minimum dose and duration of dexamethasone treatment should be strictly monitored echocardiographically for this side effect.

Betamethasone-mediated vascular dysfunction and changes in hematological profile in the ovine fetus

Glucocorticoid administration to fetal sheep induces a sustained systemic blood pressure rise and an associated increase in femoral vascular resistance. We utilized a small vessel myograph to compare isometric vascular responses of small femoral arterial branches from fetal sheep infused intravenously with either betamethasone or vehicle in vivo from 128 days gestation. Changes in hematological parameters were also determined. Betamethasone was infused for 48 h to produce fetal plasma betamethasone concentrations similar to those observed in human fetuses after maternal treatment with betamethasone to accelerate fetal lung maturation. When compared with vessels removed from vehicle-infused fetuses, vessels obtained from betamethasone-treated fetuses exhibited 1) enhanced sensitivity to depolarizing potassium solutions; 2) no differences in response to the thromboxane mimetic U-46619 or norepinephrine; and 3) differential responses to vasodilators, enhanced sensitivity to ACh, but decreased response to bradykinin and forskolin. In addition, erythrocyte and leukocyte counts were increased in betamethasone-infused fetuses. These observations indicate that multiple mechanisms operate to increase fetal vascular resistance during antenatal betamethasone exposure.