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

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.

Glucocorticoid receptor antagonization propels endogenous cardiomyocyte proliferation and cardiac regeneration

In mammals, the physiological activation of the glucocorticoid receptor (GR) by glucocorticoids (GCs) promotes the maturation of cardiomyocytes during late gestation, but the effect on postnatal cardiac growth and regenerative plasticity is unclear. Here we demonstrate that the GC-GR axis restrains cardiomyocyte proliferation during postnatal development. Cardiomyocyte-specific GR ablation in conditional knockout (cKO) mice delayed the postnatal cardiomyocyte cell cycle exit, hypertrophic growth and cytoarchitectural maturation. GR-cKO hearts showed increased expression of genes involved in glucose catabolism and reduced expression of genes promoting fatty acid oxidation and mitochondrial respiration. Accordingly, oxygen consumption in GR-cKO cardiomyocytes was less dependent on fatty acid oxidation, and glycolysis inhibition reverted GR-cKO effects on cardiomyocyte proliferation. GR ablation or transient pharmacological inhibition after myocardial infarction in juvenile and/or adult mice facilitated cardiomyocyte survival, cell cycle re-entry and division, leading to cardiac muscle regeneration along with reduced scar formation. Thus, GR restrains heart regeneration and may represent a therapeutic target.

Reawakening the Intrinsic Cardiac Regenerative Potential: Molecular Strategies to Boost Dedifferentiation and Proliferation of Endogenous Cardiomyocytes

Despite considerable efforts carried out to develop stem/progenitor cell-based technologies aiming at replacing and restoring the cardiac tissue following severe damages, thus far no strategies based on adult stem cell transplantation have been demonstrated to efficiently generate new cardiac muscle cells. Intriguingly, dedifferentiation, and proliferation of pre-existing cardiomyocytes and not stem cell differentiation represent the preponderant cellular mechanism by which lower vertebrates spontaneously regenerate the injured heart. Mammals can also regenerate their heart up to the early neonatal period, even in this case by activating the proliferation of endogenous cardiomyocytes. However, the mammalian cardiac regenerative potential is dramatically reduced soon after birth, when most cardiomyocytes exit from the cell cycle, undergo further maturation, and continue to grow in size. Although a slow rate of cardiomyocyte turnover has also been documented in adult mammals, both in mice and humans, this is not enough to sustain a robust regenerative process. Nevertheless, these remarkable findings opened the door to a branch of novel regenerative approaches aiming at reactivating the endogenous cardiac regenerative potential by triggering a partial dedifferentiation process and cell cycle re-entry in endogenous cardiomyocytes. Several adaptations from intrauterine to extrauterine life starting at birth and continuing in the immediate neonatal period concur to the loss of the mammalian cardiac regenerative ability. A wide range of systemic and microenvironmental factors or cell-intrinsic molecular players proved to regulate cardiomyocyte proliferation and their manipulation has been explored as a therapeutic strategy to boost cardiac function after injuries. We here review the scientific knowledge gained thus far in this novel and flourishing field of research, elucidating the key biological and molecular mechanisms whose modulation may represent a viable approach for regenerating the human damaged myocardium.

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.

Potential Adverse Effects of Dexamethasone Therapy on COVID-19 Patients: Review and Recommendations

In the context of the coronavirus disease 2019 (COVID-19) pandemic, the global healthcare community has raced to find effective therapeutic agents against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To date, dexamethasone is the first and an important therapeutic to significantly reduce the risk of death in COVID-19 patients with severe disease. Due to powerful anti-inflammatory and immunosuppressive effects, dexamethasone could attenuate SARS-CoV-2-induced uncontrolled cytokine storm, severe acute respiratory distress syndrome and lung injury. Nevertheless, dexamethasone treatment is a double-edged sword, as numerous studies have revealed that it has significant adverse impacts later in life. In this article, we reviewed the literature regarding the adverse effects of dexamethasone administration on different organ systems as well as related disease pathogenesis in an attempt to clarify the potential harms that may arise in COVID-19 patients receiving dexamethasone treatment. Overall, taking the threat of COVID­19 pandemic into account, we think it is necessary to apply dexamethasone as a pharmaceutical therapy in critical patients. However, its adverse side effects cannot be ignored. Our review will help medical professionals in the prognosis and follow-up of patients treated with dexamethasone. In addition, given that a considerable amount of uncertainty, confusion and even controversy still exist, further studies and more clinical trials are urgently needed to improve our understanding of the parameters and the effects of dexamethasone on patients with SARS-CoV-2 infection.

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.

Neonatal glucocorticoid overexposure alters cardiovascular function in young adult horses in a sex-linked manner

Prenatal glucocorticoid overexposure has been shown to programme adult cardiovascular function in a range of species, but much less is known about the long-term effects of neonatal glucocorticoid overexposure. In horses, prenatal maturation of the hypothalamus-pituitary-adrenal axis and the normal prepartum surge in fetal cortisol occur late in gestation compared to other precocious species. Cortisol levels continue to rise in the hours after birth of full-term foals and increase further in the subsequent days in premature, dysmature and maladapted foals. Thus, this study examined the adult cardiovascular consequences of neonatal cortisol overexposure induced by adrenocorticotropic hormone administration to full-term male and female pony foals. After catheterisation at 2-3 years of age, basal arterial blood pressures (BP) and heart rate were measured together with the responses to phenylephrine (PE) and sodium nitroprusside (SNP). These data were used to assess cardiac baroreflex sensitivity. Neonatal cortisol overexposure reduced both the pressor and bradycardic responses to PE in the young adult males, but not females. It also enhanced the initial hypotensive response to SNP, slowed recovery of BP after infusion and reduced the gain of the cardiac baroreflex in the females, but not males. Basal diastolic pressure and cardiac baroreflex sensitivity also differed with sex, irrespective of neonatal treatment. The results show that there is a window of susceptibility for glucocorticoid programming during the immediate neonatal period that alters cardiovascular function in young adult horses in a sex-linked manner.

Dexamethasone inhibits regeneration and causes ventricular aneurysm in the neonatal porcine heart after myocardial infarction

AIMS

Recently, we demonstrated that the hearts of neonatal pigs (2-day old) have regenerative capacity, likely driven by cardiac myocyte division, but this potential is lost immediately after postnatal day 3. However, it is unknown if corticosteroid, a broad anti-inflammatory agent, will abrogate the regenerative capacity in the hearts of neonatal pigs. The aim of the current study is to evaluate the effect Dexamethasone (Dex), a broad anti-inflammatory agent, on heart regeneration, structure, and function of the neonatal pigs' post-myocardial infarction (MI).

METHODS AND RESULTS

Dex (0.2 mg/kg/day) was injected intramuscularly into the neonatal pig (age: 2 days postnatal) during the first week post-MI. Myocardial scar and left ventricular function were determined by cardiac magnetic resonance (CMR) imaging. Bromodeoxyuridine (BrdU) pulse-chase labeling, histology, immunohistochemistry, and flow cytometry were performed to determine inflammatory cell infiltration, CM cytokinesis, and myocardial fibrosis. Dex injection during the first-week suppressed acute inflammation post-MI in the pig hearts. It inhibited BrdU incorporation to pig CMs and CM cytokinesis via inhibiting aurora-B protein expression which was associated with mature scar formation and thinned walls at the infarct site. CMR imaging showed Dex caused left ventricular aneurysm and poor ejection fraction.

CONCLUSIONS

Dex inhibited CM cytokinesis and functional recovery and caused ventricular aneurysm in the hearts of 2-day old pigs post-MI.

Dexamethasone Induces Cardiomyocyte Terminal Differentiation via Epigenetic Repression of Cyclin D2 Gene

Dexamethasone treatment of newborn rats inhibited cardiomyocyte proliferation and stimulated premature terminal differentiation of cardiomyocytes in the developing heart. Yet mechanisms remain undetermined. The present study tested the hypothesis that the direct effect of glucocorticoid receptor-mediated epigenetic repression of cyclin D2 gene in the cardiomyocyte plays a key role in the dexamethasone-mediated effects in the developing heart. Cardiomyocytes were isolated from 2-day-old rats. Cells were stained with a cardiomyocyte marker α-actinin and a proliferation marker Ki67. Cyclin D2 expression was evaluated by Western blot and quantitative real-time polymerase chain reaction. Promoter methylation of CcnD2 was determined by methylated DNA immunoprecipitation (MeDIP). Overexpression of Cyclin D2 was conducted by transfection of FlexiCcnD2 (+CcnD2) construct. Treatment of cardiomyocytes isolated from newborn rats with dexamethasone for 48 hours significantly inhibited cardiomyocyte proliferation with increased binucleation and decreased cyclin D2 protein abundance. These effects were blocked with Ru486 (mifepristone). In addition, the dexamethasone treatment significantly increased cyclin D2 gene promoter methylation in newborn rat cardiomyocytes. 5-Aza-2'-deoxycytidine inhibited dexamethasone-mediated promoter methylation, recovered dexamethasone-induced cyclin D2 gene repression, and blocked the dexamethasone-elicited effects on cardiomyocyte proliferation and binucleation. In addition, the overexpression of cyclin D2 restored the dexamethasone-mediated inhibition of proliferation and increase in binucleation in newborn rat cardiomyocytes. The results demonstrate that dexamethasone acting on glucocorticoid receptors has a direct effect and inhibits proliferation and stimulates premature terminal differentiation of cardiomyocytes in the developing heart via epigenetic repression of cyclin D2 gene.

Dyrk1a regulates the cardiomyocyte cell cycle via D-cyclin-dependent Rb/E2f-signalling

AIMS

Down syndrome-associated dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1A (DYRK1A) is a ubiquitously expressed protein kinase. Up to date a variety of targets have been identified, establishing a key role for Dyrk1a in selected signalling pathways. In cardiomyocytes, Dyrk1a acts as a negative regulator of hypertrophy by phosphorylating transcription factors of the NFAT family, but its mechanistic function in the heart remains poorly understood. This study was designed to investigate a potential protective role of Dyrk1a in cardiac hypertrophy in vivo.

METHODS AND RESULTS

We generated transgenic mice with cardiac-specific overexpression of Dyrk1a. Counterintuitively, these mice developed severe dilated cardiomyopathy associated with congestive heart failure and premature death. In search for the cause of this unexpected phenotype, we found that Dyrk1a interacts with all members of the D-cyclin family and represses their protein levels in vitro and in vivo. Particularly, forced expression of Dyrk1a leads to increased phosphorylation of Ccnd2 on Thr280 and promotes its subsequent proteasomal degradation. Accordingly, cardiomyocytes overexpressing Dyrk1a display hypo-phosphorylated Rb1, suppression of Rb/E2f-signalling, and reduced expression of E2f-target genes, which ultimately results in impaired cell cycle progression.

CONCLUSIONS

We identified Dyrk1a as a novel negative regulator of D-cyclin-mediated Rb/E2f-signalling. As dysregulation of this pathway with impaired cardiomyocyte proliferation leads to cardiomyopathy, dose-specific Dyrk1a expression and activity appears to be critical for the hyperplastic and hypertrophic growth of the developing heart.

Cardiac GR and MR: From Development to Pathology

The efficacy of mineralocorticoid receptor (MR) antagonism in the treatment of certain patients with heart failure has highlighted the pivotal role of aldosterone and MR in heart disease. The glucocorticoid (GC) receptor (GR) is also expressed in heart, but the role of cardiac GR had received much less attention until recently. GR and MR are highly homologous in both structure and function, although not in cellular readout. Recent evidence in animal models has uncovered a tonic role for GC action via GR in cardiomyocytes in prevention of heart disease. Here, we review this evidence and the implications for a balance between GR and MR activation in the early life maturation of the heart and its subsequent health and disease.

Effects of glucocorticoid exposure on growth and structural maturation of the heart of the preterm piglet

Inadequate maintenance of systemic blood flow in neonates following preterm birth is associated with increased morbidity and mortality, and may be due in part to structural immaturity of the myocardium. Maternal glucocorticoid administration is associated with improved cardiovascular function, and possibly promotes structural maturation of the myocardium. This study assessed the structural maturity of the myocardium in male and female preterm and term piglets, and preterm piglets exposed to a regimen of maternal glucocorticoids as used clinically. In preterm, term and glucocorticoid exposed preterm piglets cardiomyocyte maturity was examined by measuring the proportion of binucleated myocytes and the volumes of single living ventricular cardiomyocytes with fluorescence microscopy. Ventricular apoptosis and proliferation were measured by immunohistochemistry. Preterm piglet hearts had fewer binucleated myocytes, smaller myocytes, and more proliferative and fewer apoptotic nuclei than term hearts. Maternal glucocorticoid treatment resulted in increased binucleation with no increase in myocyte volume, and levels of proliferation and apoptosis that were more similar to the term heart. Atrial weights were increased and in female piglets there was an increase in the ratio of left to right ventricular weight. The observed changes in atrial mass and myocyte structural maturation correlated with changes in cardiac function of isolated hearts of littermates. In conclusion, the association between increased myocardial maturation following glucocorticoid exposure, improved cardiac function in littermates, and clinical improvement in human neonatal cardiac function exposed to antenatal glucocorticoids, suggests that glucocorticoid exposure contributes to improved cardiovascular function in preterm infants by promoting myocardial structural maturity.

Binucleation of cardiomyocytes: the transition from a proliferative to a terminally differentiated state

Cardiomyocytes possess a unique ability to transition from mononucleate to the mature binucleate phenotype in late fetal development and around birth. Mononucleate cells are proliferative, whereas binucleate cells exit the cell cycle and no longer proliferate. This crucial period of terminal differentiation dictates cardiomyocyte endowment for life. Adverse early life events can influence development of the heart, affecting cardiomyocyte number and contributing to heart disease late in life. Although much is still unknown about the mechanisms underlying the binucleation process, many studies are focused on molecules involved in cell cycle regulation and cytokinesis as well as epigenetic modifications that can occur during this transition. Better understanding of these mechanisms could provide a basis for recovering the proliferative capacity of cardiomyocytes.

Antioxidant treatment improves neonatal survival and prevents impaired cardiac function at adulthood following neonatal glucocorticoid therapy

Glucocorticoids are widely used to treat chronic lung disease in premature infants but their longer-term adverse effects on the cardiovascular system raise concerns. We reported that neonatal dexamethasone treatment in rats induced in the short term molecular indices of cardiac oxidative stress and cardiovascular tissue remodelling at weaning, and that neonatal combined antioxidant and dexamethasone treatment was protective at this time. In this study, we investigated whether such effects of neonatal dexamethasone have adverse consequences for NO bioavailability and cardiovascular function at adulthood, and whether neonatal combined antioxidant and dexamethasone treatment is protective in the adult. Newborn rat pups received daily i.p. injections of a human-relevant tapering dose of dexamethasone (D; n = 8; 0.5, 0.3, 0.1 μg g(-1)) or D with vitamins C and E (DCE; n = 8; 200 and 100 mg kg(-1), respectively) on postnatal days 1-3 (P1-3); vitamins were continued from P4 to P6. Controls received equal volumes of vehicle from P1 to P6 (C; n = 8). A fourth group received vitamins alone (CCE; n = 8). At P100, plasma NO metabolites (NOx) was measured and isolated hearts were assessed under both Working and Langendorff preparations. Relative to controls, neonatal dexamethasone therapy increased mortality by 18% (P < 0.05). Surviving D pups at adulthood had lower plasma NOx concentrations (10.6 ± 0.8 vs. 28.0 ± 1.5 μM), an increased relative left ventricular (LV) mass (70 ± 2 vs. 63 ± 1%), enhanced LV end-diastolic pressure (14 ± 2 vs. 8 ± 1 mmHg) and these hearts failed to adapt output with increased preload (cardiac output: 2.9 ± 2.0 vs. 10.6 ± 1.2 ml min(-1)) or afterload (cardiac output: -5.3 ± 2.0 vs.1.4 ± 1.2 ml min(-1)); all P < 0.05. Combined neonatal dexamethasone with antioxidant vitamins improved postnatal survival, restored plasma NOx and protected against cardiac dysfunction at adulthood. In conclusion, neonatal dexamethasone therapy promotes cardiac dysfunction at adulthood. Combined neonatal treatment with antioxidant vitamins is an effective intervention.

Antioxidant treatment alters peripheral vascular dysfunction induced by postnatal glucocorticoid therapy in rats

BACKGROUND

Postnatal glucocorticoid therapy in premature infants diminishes chronic lung disease, but it also increases the risk of hypertension in adulthood. Since glucocorticoid excess leads to overproduction of free radicals and endothelial dysfunction, this study tested the hypothesis that adverse effects on cardiovascular function of postnatal glucocorticoids are secondary to oxidative stress. Therefore, combined postnatal treatment of glucocorticoids with antioxidants may diminish unwanted effects.

METHODOLOGY/PRINCIPAL FINDINGS

Male rat pups received a course of dexamethasone (Dex), or Dex with vitamins C and E (DexCE), on postnatal days 1-6 (P1-6). Controls received vehicle (Ctrl) or vehicle with vitamins (CtrlCE). At P21, femoral vascular reactivity was determined via wire myography. Dex, but not DexCE or CtrlCE, increased mortality relative to Ctrl (81.3 versus 96.9 versus 90.6 versus 100% survival, respectively; P<0.05). Constrictor responses to phenylephrine (PE) and thromboxane were enhanced in Dex relative to Ctrl (84.7+/-4.8 versus 67.5+/-5.7 and 132.7+/-4.9 versus 107.0+/-4.9% Kmax, respectively; P<0.05); effects that were diminished in DexCE (58.3+/-7.5 and 121.1+/-4.3% Kmax, respectively; P<0.05). Endothelium-dependent dilatation was depressed in Dex relative to Ctrl (115.3+/-11.9 versus 216.9+/-18.9, AUC; P<0.05); however, this effect was not restored in DexCE (68.3+/-8.3, AUC). Relative to Ctrl, CtrlCE alone diminished PE-induced constriction (43.4+/-3.7% Kmax) and the endothelium-dependent dilatation (74.7+/-8.7 AUC; P<0.05).

CONCLUSIONS/SIGNIFICANCE

Treatment of newborn rats with dexamethasone has detrimental effects on survival and peripheral vasoconstrictor function. Coadministration of dexamethasone with antioxidant vitamins improves survival and partially restores vascular dysfunction. Antioxidant vitamins alone affect peripheral vascular function.

Neonatal dexamethasone treatment in the rat leads to kidney damage in adulthood

Recently, concern has been raised that corticosteroid treatment of preterm neonates might be associated with adverse effects later in life, including early development of hypertension. Here, we investigate the impact of neonatal dexamethasone (Dex) treatment on early renal cell proliferation and nephron number. We analyzed mitotic activity in renal cortex of rat pups neonatally treated with Dex. Nephron number was measured and possible renal damage was quantified by counting inflammatory foci, ED-1 positive cells (macrophages), and the desmin score (activated podocytes). Mitotic activity was 34 and 29% lower on d 2 and 4 in Dex-treated rats compared with saline-treated controls. The number of glomeruli was lower at 4 wk, but nephron size was unchanged after Dex treatment, as calculated from glomerular density and (lower) body- and kidney weight. At wk 50, the glomerular number was significantly lower in Dex-treated rats, whereas body and kidney weight were the same as in Sal controls. Dex rats also showed more kidney damage, manifested by a approximately 3.5-fold increase in inflammation foci/mm and in ED-1 positive cells/mm and a approximately 4.3-fold increased desmin score. Temporary suppression of mitotic activity during neonatal Dex treatment leads to reduction of nephron number and more kidney damage later in life.

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.

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.

Effects of neonatal dexamethasone treatment on the cardiovascular stress response of children at school age

OBJECTIVE

The goal was to investigate cardiovascular responses to a psychosocial stressor in school-aged, formerly premature boys and girls who had been treated neonatally with dexamethasone or hydrocortisone because of chronic lung disease.

METHODS

We compared corticosteroid-treated, formerly preterm infants with formerly preterm infants who had not been treated neonatally with corticosteroids (reference group). Children performed the Trier Social Stress Test for Children, which includes a public speaking task and a mental arithmetic task. Blood pressure was recorded continuously before, during, and after the stress test. Plasma norepinephrine levels were determined before the test, directly after the stress task, and after recovery.

RESULTS

Overall, in response to stress, girls had significantly larger changes in systolic blood pressure and mean arterial pressure and in stroke volume and cardiac output, compared with boys. Boys exhibited larger total peripheral resistance responses, compared with girls. The hydrocortisone group did not differ significantly from the reference group in any of the outcome measures. However, dexamethasone-treated children had smaller stress-induced increases in systolic and mean arterial blood pressure than did hydrocortisone-treated children. In addition, the dexamethasone group showed smaller increases in stroke volume and blunted norepinephrine responses to stress, compared with children in the reference group. Correction for gender did not affect these results.

CONCLUSIONS

The differences in cardiovascular stress responses between girls and boys are consistent with known gender differences in adult cardiovascular stress responses. Our data demonstrate that neonatal treatment with dexamethasone has long-term consequences for the cardiovascular and noradrenergic stress responses; at school age, the cardiovascular stress response was blunted in dexamethasone-treated children. Hydrocortisone-treated children did not differ from the reference group, which suggests that hydrocortisone might be a safe alternative to dexamethasone for treating chronic lung disease of prematurity.

Early origins of cardiac hypertrophy: does cardiomyocyte attrition programme for pathological 'catch-up' growth of the heart?

1. Epidemiological and experimental evidence suggests that adult development of cardiovascular disease is influenced by events of prenatal and early postnatal life. Cardiac hypertrophy is recognized as an important predictor of cardiovascular morbidity and mortality, but the developmental origins of this condition are not well understood. 2. In the heart, a switch from hyperplastic to hypertrophic cellular growth occurs during late prenatal or early postnatal life. Postnatal growth of the heart is almost entirely reliant on hypertrophy of individual cardiomyocytes, and damage to heart muscle in adulthood is typically not reparable by cell replacement. Therefore, a reduced number of cardiomyocytes may render the heart more vulnerable in situations where an increased workload is required. 3. A number of different animal models have been used to study fetal programming of adult diseases, including nutritional, hypoxic, maternal/neonatal endocrine stress and genetic models. Although studies investigating the cellular basis of myocardial disease in growth-restricted models are limited, a reduction in cardiomyocyte number through either reduced cellular proliferation or increased apoptosis appears to be a central feature. 4. The mechanisms responsible for the programming of adult cardiovascular disease are poorly understood. We hypothesize that cardiac hypertrophy can have a developmental origin in excess cardiomyocyte attrition during a critical perinatal growth window. Findings that have directly assessed the impact of fetal growth restriction on the myocardium are considered and cellular and molecular mechanisms involved in the potential pathological 'catch-up' growth of the heart during later maturation are identified.

Neonatal dexamethasone treatment for chronic lung disease of prematurity alters the hypothalamus-pituitary-adrenal axis and immune system activity at school age

OBJECTIVE

To compare long-term effects of neonatal treatment with dexamethasone or hydrocortisone for chronic lung disease of prematurity on the hypothalamus-pituitary-adrenal axis and the immune response in children at school age.

PATIENTS AND METHODS

A total of 156 prematurely born children were included in this retrospective matched cohort study. Children treated with dexamethasone (n = 52) or hydrocortisone (n = 52) were matched for gestational age, birth weight, grade of infant respiratory distress syndrome, grade of periventricular or intraventricular hemorrhage, gender, and year of birth. A reference group of 52 children not treated with corticosteroids was included for comparison. Plasma adrenocorticotropic hormone and cortisol in response to a social stress task were determined. Cytokine production was analyzed after in vitro stimulation of whole-blood cultures.

RESULTS

The Trier Social Stress Test adapted for children induced an adrenocorticotropic hormone and cortisol response in all of the groups. The adrenocorticotropic hormone response was blunted in the dexamethasone group. The overall cortisol level was lower in the dexamethasone than in the hydrocortisone and reference group. Cortisol and adrenocorticotropic hormone in the hydrocortisone and reference groups were similar. The ratio of T-cell mitogen-induced interferon-gamma/interleukin-4 secretion was significantly higher in the dexamethasone group than in the hydrocortisone group. Interferon-gamma production and the ratios of interferon-gamma/interleukin-4 and interferon-gamma/ interleukin-10 were significantly higher in the dexamethasone group than the reference group. However, production of these cytokines did not differ between the hydrocortisone and the reference groups.

CONCLUSION

Neonatal treatment of prematurely born children with dexamethasone but not with hydrocortisone resulted in long-lasting programming effects on hypothalamus-pituitary-adrenal axis and on the T-helper 1/T-helper 2 cytokine balance. Follow-up of these children is required to investigate long-term clinical consequences. We recommend that authors of previously performed randomized, controlled trials on neonatal glucocorticoid treatment include immune and neuroendocrine analyses in prolonged follow-up of these children.

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.

Postnatal treatment with dexamethasone perturbs hepatic and cardiac energy metabolism and is associated with a sustained atherogenic plasma lipid profile in suckling rats

Early exposure to glucocorticoids (GC) has been proposed to disturb hepatic and cardiac function in later life. In the present study, we evaluated early metabolic alterations upon GC treatment that may predispose to long-term abnormalities. Rats were injected with dexamethasone (DEX) at d 1, 2, and 3 after birth and controls received saline (SAL). Rats were killed at 2, 7, and 14 d of age. Compared with SAL, DEX induced lower plasma insulin levels, hyperglycemia, hyperketonemia, and dyslipidemia at 2 d. At the same time, DEX treatment significantly increased expression of gluconeogenic and fatty acid oxidation genes in liver and expression of genes involved fatty acid utilization in heart. At 7 d, DEX-treated rats showed insulin resistance with hyperlipidemia, whereas hepatic and cardiac gene expression patterns were largely normalized. Hyperlipidemia and a significantly increased hepatic triglyceride content in DEX-treated rats were prominent at 14 d without large differences in hepatic and cardiac gene expression patterns. Thus, neonatal DEX administration transiently affects cardiac and hepatic gene expression patterns in suckling rats associated with sustained effects on plasma glucose and lipid concentrations. Whether these early effects of DEX contribute to hepatic and cardiac abnormalities at adult age needs further evaluation.

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.