Fetal dexamethasone exposure interferes with establishment of cardiac noradrenergic innervation and sympathetic activity

Chronic maternal hypercortisolemia models stress-induced adverse birth outcome and altered cardiac function in newborn lambs

Maternal stress in pregnancy is thought to be a contributing factor in adverse pregnancy outcome, including stillbirth and prematurity. Previous studies in our laboratory have shown that chronic elevation in maternal cortisol concentration in ewes (by maternal infusion of 1 mg·kg^-1·day^-1) during the late gestion increased the incidence of stillbirth and altered fetal heart rate and blood pressure at birth. We designed the current study to test the effect of chronically elevated maternal cortisol on fetal cardiac adaption from in utero life to ex utero life. The combined risk of stillbirth or prematurity was significantly greater in the pregnancies with maternal hypercortisolemia: in this cohort, 40% of the lambs of cortisol-infused ewes died in utero or at birth compared to 25% of lambs of control ewes, and 24% of lambs of cortisol-infused ewes were born preterm, whereas no lamb was born preterm in the control group. Compared to control lambs, the lambs of cortisol-infused ewes born at full term exhibited a significant increase in mean aortic pressure just prior to birth, and a significant decrease in mean aortic pressure that was evident during the first 9 hours after birth. The QT interval was decreased prior to birth and increased immediately after birth in the newborns of cortisol-treated ewes compared to control lambs. These findings suggest that an excess in utero corticosteroid exposure adversely affects fetal cardiac adaptation to extrauterine life and that chronic maternal stress or hypersecretion of corticosteroids may contribute to adverse obstetric outcomes.

Prenatal therapeutics and programming of cardiovascular function

Cardiovascular diseases (CVD) are a leading cause of mortality worldwide. Despite recognizing the importance of risk factors in dictating CVD susceptibility and onset, patient treatment remains a challenging endeavor. Increasingly, the benefits of prevention and mitigation of risk factors earlier in life are being acknowledged. The developmental origins of health and disease posits that insults during specific periods of development can influence long-term health outcomes; this occurs because the developing organism is highly plastic, and hence vulnerable to environmental perturbations. By extension, targeted therapeutics instituted during critical periods of development may confer long-term protection, and thus reduce the risk of CVD in later life. This review provides a brief overview of models of developmental programming, and then discusses the impact of perinatal therapeutic interventions on long-term cardiovascular function in the offspring. The discussion focuses on bioactive food components, as well as pharmacological agents currently approved for use in pregnancy; in short, those agents most likely to be used in pregnancy and early childhood.

Antenatal steroid exposure and heart rate variability in adolescents born with very low birth weight

BACKGROUND

Reduced heart rate variability (HRV) suggests autonomic imbalance in the control of heart rate and is associated with unfavorable cardiometabolic outcomes. We examined whether antenatal corticosteroid (ANCS) exposure had long-term programming effects on HRV in adolescents born with very low birth weight (VLBW).

METHODS

Follow-up study of a cohort of VLBW 14-y olds born between 1992 and 1996 with 50% exposed to ANCS. HRV in both the time and frequency domains using Nevrokard Software was determined from a 5-min electrocardiogram tracing.

RESULTS

HRV data from 89 (35 male, 53 non-black) exposed (ANCS+) and 77 (28 male, 29 non-black) unexposed (ANCS-) adolescents were analyzed. HRV did not differ between ANCS+ and ANCS- black participants. However, in non-black participants, a significant interaction between ANCS and sex was observed, with ANCS- females having significantly greater HRV than ANCS+ females and males, and ANCS- males for both time and frequency domain variables.

CONCLUSION

Among non-black adolescents born with VLBW, ANCS exposure is associated with reduced HRV with apparent sex-specificity. Reduced HRV has been associated with development of adverse cardiometabolic outcomes, thus supporting the need to monitor these outcomes in VLBW adolescents as they mature.

Nutrition for Multiples

In 2012 there were 135,943 infants of multiple pregnancies born in the United States, nearly a 2-fold increase since 1980, with twins accounting for 96% of all multiple births. To date, most perinatal morbidities associated with multiple births have proven resistant to technological or pharmaceutical interventions. Maternal nutrition can have a profound effect on the course and outcome of multiple pregnancy, with the goal of achieving optimal intrauterine growth and birthweights, and minimizing prenatal and perinatal complications for the mother and her children.

Diminished 11β-hydroxysteroid dehydrogenase type 2 activity is associated with decreased weight and weight gain across the first year of life

CONTEXT

Low birth weight is associated with adverse metabolic outcome in adulthood. Exposure to glucocorticoid (GC) excess in utero is associated with decreased birth weight, but the prospective longitudinal relationship between GC metabolism and growth has not been examined.

OBJECTIVE

We have hypothesized that changes in GC metabolism leading to increased availability may impair growth.

DESIGN

This was a prospective, longitudinal study with clinical measurements and 24-hour urinary steroid metabolite analysis at 1, 4, 12, 26, and 52 weeks after delivery in mothers and their babies.

SETTING

The study was conducted with observations and samples collected in the volunteers' own homes.

PARTICIPANTS

Healthy mothers and newborn babies/infants participated in the study.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

Urinary steroid metabolite excretion quantified by gas chromatography/mass spectroscopy across the first year of life in relation to change in weight was measured.

RESULTS

The total production of the GC metabolites quantified increased across the first year of life. Markers of 11β-hydroxysteroid dehydrogenase type 1 activity increased from the age of 3 months as did those of 5α-reductase activity. After correcting for confounding variables, low markers of 11β-hydroxysteroid dehydrogenase type 2 activity was associated with reduced absolute weight and decreased weight gain over the first year of life. In the mothers, 5α-reductase activity was low at birth and progressively increased to normal over the first 6 months postpartum.

CONCLUSIONS

Increased GC exposure as a consequence of reduced 11β-hydroxysteroid dehydrogenase type 2 activity is likely to be a critical determinant of growth in early life. This not only highlights the central role of GCs and their metabolism, but also emphasizes the need for detailed longitudinal analyses.

Glucocorticoids and foetal heart maturation; implications for prematurity and foetal programming

Glucocorticoids are steroid hormones, essential in mammals to prepare for life after birth. Blood levels of glucocorticoids (cortisol in most mammals including humans; corticosterone in rats and mice) rise dramatically shortly before birth. This is mimicked clinically in the routine administration of synthetic glucocorticoids to pregnant women threatened by a preterm birth or to preterm infants to improve neonatal survival. Whilst effects on lung are well documented and essential for postnatal survival, those on heart are less well known. In this study, we review recent evidence for a crucial role of glucocorticoids in late gestational heart maturation. Either insufficient or excessive glucocorticoid exposure before birth may alter the normal glucocorticoid-regulated trajectory of heart maturation with potential life-long consequences.

Glucocorticoid programming of the fetal male hippocampal epigenome

The late-gestation surge in fetal plasma cortisol is critical for maturation of fetal organ systems. As a result, synthetic glucocorticoids (sGCs) are administered to pregnant women at risk of delivering preterm. However, animal studies have shown that fetal exposure to sGC results in increased risk of behavioral, endocrine, and metabolic abnormalities in offspring. Here, we test the hypothesis that prenatal GC exposure resulting from the fetal cortisol surge or after sGC exposure results in promoter-specific epigenetic changes in the hippocampus. Fetal guinea pig hippocampi were collected before (gestational day [GD52]) and after (GD65) the fetal plasma cortisol surge (Term∼GD67) and 24 hours after (GD52) and 14 days after (GD65) two repeat courses of maternal sGC (betamethasone) treatment (n = 3-4/gp). We identified extensive genome-wide alterations in promoter methylation in late fetal development (coincident with the fetal cortisol surge), whereby the majority of the affected promoters exhibited hypomethylation. Fetuses exposed to sGC in late gestation exhibited substantial differences in DNA methylation and histone h3 lysine 9 (H3K9) acetylation in specific gene promoters; 24 hours after the sGC treatment, the majority of genes affected were hypomethylated or hyperacetylated. However, 14 days after sGC exposure these differences did not persist, whereas other promoters became hypermethylated or hyperacetylated. These data support the hypothesis that the fetal GC surge is responsible, in part, for significant variations in genome-wide promoter methylation and that prenatal sGC treatment profoundly changes the epigenetic landscape, affecting both DNA methylation and H3K9 acetylation. This is important given the widespread use of sGC in the management of women in preterm labor.

Glucocorticoids as mediators of developmental programming effects

Epidemiological evidence suggests that exposure to an adverse environment in early life is associated with an increased risk of cardio-metabolic and behavioral disorders in adulthood, a phenomenon termed 'early life programming'. One major hypothesis for early life programming is fetal glucocorticoid overexposure. In animal studies, prenatal glucocorticoid excess as a consequence of maternal stress or through exogenous administration to the mother or fetus is associated with programming effects on cardiovascular and metabolic systems and on the brain. These effects can be transmitted to subsequent generations. Studies in humans provide some evidence that prenatal glucocorticoid exposure may exert similar programming effects on glucose/insulin homeostasis, blood pressure and neurodevelopment. The mechanisms by which glucocorticoids mediate these effects are unclear but may include a role for epigenetic modifications. This review discusses the evidence for glucocorticoid programming in animal models and in humans.

Prenatal stress and balance of the child's cardiac autonomic nervous system at age 5-6 years

OBJECTIVE

Autonomic nervous system (ANS) misbalance is a potential causal factor in the development of cardiovascular disease. The ANS may be programmed during pregnancy due to various maternal factors. Our aim is to study maternal prenatal psychosocial stress as a potential disruptor of cardiac ANS balance in the child.

METHODS

Mothers from a prospective birth cohort (ABCD study) filled out a questionnaire at gestational week 16 [IQR 12-20], that included validated instruments for state anxiety, depressive symptoms, pregnancy-related anxiety, parenting daily hassles and job strain. A cumulative stress score was also calculated (based on 80(th) percentiles). Indicators of cardiac ANS in the offspring at age 5-6 years are: pre-ejection period (PEP), heart rate (HR), respiratory sinus arrhythmia (RSA) and cardiac autonomic balance (CAB), measured with electrocardiography and impedance cardiography in resting supine and sitting positions.

RESULTS

2,624 mother-child pairs, only single births, were available for analysis. The stress scales were not significantly associated with HR, PEP, RSA and CAB (p≥0.17). Accumulation of maternal stress was also not associated with HR, PEP, RSA and CAB (p≥0.07).

CONCLUSION

Results did not support the hypothesis that prenatal maternal psychosocial stress deregulates cardiac ANS balance in the offspring, at least in rest, and at the age of five-six years.

Effect of antenatal betamethasone administration on neonatal cardiac autonomic balance

Beneficial effects of antenatal glucocorticoid treatment in pregnancies at risk for preterm delivery may entail long-term consequences for the establishment of sympathoadrenergic system balance. We analyzed the cardiac autonomic system activity in neonates with a single course of antenatal betamethasone (2 × 12 mg) treatment by calculating heart rate variability (HRV) time-domain parameters from 24 h ECG recordings and short-term frequency-domain parameters during infant active and resting states. In addition, resting and challenged salivary α-amylase levels were measured in 23 betamethasone-exposed neonates and compared with controls. Indicators for overall HRV (SDNN: p = 0.258; triangular index: p = 0.179) and sympathovagal balance [low- to high-frequency power (LF/HF): p = 0.82 (resting state)] were not significantly different in neonates of the betamethasone treatment group. Parameters mostly influenced by sympathetic activity [SD of the average of valid NN intervals (SDANN): p = 0.184 and SDs of all NN intervals (SDNNi): p = 0.784] and vagal tone [RMSSD: p = 1.0; NN50: p = 0.852; HF: p = 0.785 (resting state)] were unaltered. Resting α-amylase levels were not significantly different in the betamethasone treatment group (p = 0.304); however, α-amylase release after a neonatal challenge was slightly reduced (p = 0.045). Thus, cardiac autonomic balance seems to be preserved in neonates exposed to a single course of antenatal betamethasone treatment.

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.

Cardiac autonomic balance in small-for-gestational-age neonates

The cardiac sympathetic nervous system is one putative key factor involved in the intrauterine programming of adult cardiovascular disease. We therefore analyzed cardiac autonomic system activity in small for gestational age (SGA) neonates. Heart rate variability (HRV) from 24-h ECG recordings were analyzed for time-domain and frequency-domain parameters in 27 SGA neonates [median 261 (240–283) days of gestation] compared with 27 appropriate for gestational age (AGA) neonates [median 270 (239–293) days of gestation]. In addition, salivary α-amylase levels were analyzed during resting conditions and in response to a pain-induced stress event in 18 SGA [median 266 (240–292) days of gestation] and 34 AGA [median 271 (240–294) days of gestation] neonates. Overall HRV was not significantly different in SGA neonates compared with AGA neonates (SD of all valid NN intervals: P = 0.14; triangular index: P = 0.29), and the sympathovagal balance [low frequency (LF)/high frequency (HF)] was similar ( P = 0.62). Parameters mostly influenced by sympathetic activity did not reveal significant differences: (SD of the average of valid NN intervals: P = 0.27; average of the hourly means of SDs of all NN intervals: P = 0.66, LF: P = 0.83) as well as vagal tone-influenced parameters were unaltered (average of the hourly square root of the mean of the sum of the squares of differences between adjacent NN intervals: P = 0.59; proportion of pairs of adjacent NN intervals differing by >50 ms: P = 0.93; HF: P = 0.82). Median resting levels for α-amylase were not significantly different in SGA neonates ( P = 0.13), and a neonatal stress stimulus revealed similar stress response patterns ( P = 0.29). HRV and salivary α-amylase levels as indicators of cardiac autonomic activity were not altered in SGA neonates compared with AGA neonates. Thus, it appears that the intrauterine activation of the sympathetic system in SGA fetuses does not directly persist into postnatal life, and neonatal sympathovagal balance appears to be preserved.

Prenatal dexamethasone 'programmes' hypotension, but stress-induced hypertension in adult offspring

Low birth weight in humans is predictive of hypertension in adult life. Although the mechanisms underlying this link remain unknown, fetal overexposure to glucocorticoids has been implicated. We previously showed that prenatal dexamethasone (DEX) exposure in the rat lowers birth weight and programmes adult hypertension. The current study aimed to further investigate the nature of this hypertension and to elucidate its origins. Unlike previous studies, we assessed offspring blood pressure (BP) with radiotelemetry, which is unaffected by stress artefacts of measurement. We show that prenatal DEX during the last week of pregnancy results in offspring of low birth weight (14% reduction) that have lower basal BP in adulthood ( approximately 4-8 mmHg lower); with the commonly expected hypertensive phenotype only being noted when these offspring are subjected to even mild disturbance or a more severe stressor (up to 30 mmHg higher than controls). Moreover, DEX-treated offspring sustain their stress-induced hypertension for longer. Promotion of systemic catecholamine release (amphetamine) induced a significantly greater rise of BP in the DEX animals (77% increase) over that observed in the vehicle controls. Additionally, we demonstrate that the isolated mesenteric vasculature of DEX-treated offspring display greater sensitivity to noradrenaline and other vasoconstrictors. We therefore conclude that altered sympathetic responses mediate the stress-induced hypertension associated with prenatal DEX programming.

Mechanisms underlying the role of glucocorticoids in the early life programming of adult disease

Compelling epidemiological evidence suggests that exposure to an adverse intrauterine environment, manifested by low-birth weight, is associated with cardiometabolic and behavioural disorders in adulthood. These observations have led to the concept of ‘fetal programming’. The molecular mechanisms that underlie this relationship remain unclear, but are being extensively investigated using a number of experimental models. One major hypothesis for early life physiological programming implicates fetal overexposure to stress (glucocorticoid) hormones. Several animal studies have shown that prenatal glucocorticoid excess, either from endogenous overproduction with maternal stress or through exogenous administration to the mother or fetus, reduces birth weight and causes lifelong hypertension, hyperglycaemia and behavioural abnormality in the offspring. Intriguingly, these effects are transmitted across generations without further exposure to glucocorticoids, which suggests an epigenetic mechanism. These animal observations could have huge implications if extrapolated to humans, where glucocorticoids have extensive therapeutic use in obstetric and neonatal practice.

Epigenetic mechanisms of perinatal programming of hypothalamic-pituitary-adrenal function and health

Environmental effects on the materno-foetal interaction determine birth outcomes that predict health over the lifespan. Thus, maternal undernutrition or stress associate with low birth weight, leading to an increased risk of metabolic and cardiovascular illness in the offspring. We argue that these effects are, in part, mediated by direct and indirect effects on the hypothalamic-pituitary-adrenal (HPA) axis such that (i) the effect of maternal adversity on foetal growth is mediated by adrenal glucocorticoids and (ii) environmental adversity alters maternal physiology and behaviour, which then programs HPA activity in the offspring.

Cardiovascular reactivity to psychological stressors in late adulthood is predicted by gestational age at birth

The relationships of body size and gestational age at birth with adult blood pressure (BP) are relatively modest compared to their stronger associations with cardiovascular disease. BP reactivity is a strong predictor of cardiovascular morbidity, and it is possible that reactivity, rather than resting level, is determined in utero. We investigated whether body size and gestational age at birth predict BP reactivity during experimentally induced psychosocial stress in late adulthood. A total of 73 men and 80 women born after 36 weeks' gestation in Helsinki, Finland, during 1934-1944 underwent the Trier Social Stress Test (TSST); a standardized psychosocial stress test consisting of a public speech and an arithmetic task. Changes in BP were monitored continuously by a non-invasive finger photoplethysmography (Finometer, FMS, Amsterdam, The Netherlands). The results showed that the most robust early determinant of BP reactivity was gestational age; however, with opposite relationships between the sexes (P for interaction <0.001). A 1-week increase in gestational age was associated with a 3.1 mm Hg (95% confidence interval (CI), 0.2 to 6.0) and 1.2 mm Hg (95% CI, -0.1 to 2.6) decreases in systolic and diastolic BP reactivity in women, but with 5.2 mm Hg (95% CI, 1.9 to 8.4) and 2.3 mm Hg (95% CI, 0.9 to 3.8) increases in men. In conclusion, normal variation in gestational age at birth predicts cardiovascular stress reactivity in later adulthood. Given that hypothalamic-pituitary-adrenal axis contributes to the regulation of autonomic nervous system function and the timing of parturition, and shows well-established sex differences, we speculate a role for early programming of this axis in explaining the findings.

Developmental origins of obesity: a sympathoadrenal perspective

Environmental exposures at crucial points in development permanently alter sympathoadrenal function in mammals. Both the sympathetic innervation of peripheral tissues and the responsiveness of sympathetic nerves and adrenal medulla to standard stimuli are susceptible to modification by exposures in early life. Several conditions studied in the laboratory, including environmental temperature, litter size and maternal nutrition, in addition to affecting sympathoadrenal function also produce larger, fatter offspring, raising the possibility that developmental programming of the sympathetic nervous system (SNS) may contribute to acquisition of an obese phenotype. The specific changes noted in all three circumstances include evidence of an increase in sympathetic innervation in pancreas and retroperitoneal fat. By contrast, SNS development is impaired in experimental models of intrauterine growth retardation. Although the physiological implications of increased sympathetic innervation in pancreas and retroperitoneal fat are not fully understood, these changes seen in animals reared at cool temperatures, in small litters or by mothers fed refined carbohydrate diets likely reflect an early enhancement of the offspring's capacity to take up and store glucose. If so, the tendency of these animals to gain weight and accumulate fat may represent an adaptive response to 'over-nutrition' in early life.

Glucocorticoid "Programming" and PTSD Risk

Epidemiological data have linked an adverse fetal environment with increased risks of cardiovascular, metabolic, neuroendocrine, and psychiatric disorders in adulthood. Prenatal stress and/or glucocorticoid excess might underlie this link. In animal models, prenatal stress, glucocorticoid exposure or inhibition/knockout of 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD-2), the feto-placental barrier to maternal glucocorticoids, reduces birth weight and causes permanent hypertension, hyperglycemia, increased hypothalamic-pituitary-adrenal (HPA) axis activity and behavior resembling of anxiety. In humans, 11 beta-HSD-2 gene mutations cause low birth weight and placental 11 beta-HSD-2 activity correlates directly with birth weight and inversely with infant blood pressure. Low birth weight babies have higher plasma cortisol levels throughout adult life, indicating HPA programming. In human pregnancy, severe maternal stress affects the offspring HPA axis and associates with neuropsychiatric disorders. Posttraumatic stress disorder (PTSD) appears to be a variable in the effects. Intriguingly, some of these effects appear to be 'inherited' into a further generation, itself unexposed to exogenous glucocorticoids at any point in the lifespan from fertilization, implying epigenetic marks persist into subsequent generation(s). Overall, the data suggest that prenatal exposure to excess glucocorticoids programs peripheral and CNS functions in adult life, predisposing to some pathologies, perhaps protecting from others, and these may be transmitted perhaps to one or two subsequent generations.

Prenatal glucocorticoid exposure and physiological programming of adult disease

Compelling epidemiological evidence suggests that the early environment is an important determinant of later risk of disease. In particular, low birth weight has been associated with an increased risk of cardiovascular and metabolic disorders, including hypertension, Type 2 diabetes mellitus and ischemic heart disease, independent of classical adult lifestyle risk factors such as smoking, adult weight, social class, excess alcohol intake and sedentary lifestyle. These observations have led to a revolutionary concept of early life physiological programming. The molecular mechanisms that underlie this relationship remain unclear, but one major hypothesis implicates fetal overexposure to glucocorticoid stress hormones. This article will review evidence for this hypothesis.

Activation of the hypothalamic-pituitary-adrenal axis and autonomic nervous system during inflammation and altered programming of the neuroendocrine-immune axis during fetal and neonatal development: lessons learned from the model inflammagen, lipopolysaccharide

The hypothalamic-pituitary-adrenal axis (HPAA) and autonomic nervous system (ANS) are both activated during inflammation as an elaborate multi-directional communication pathway designed to restore homeostasis, in part, by regulating the inflammatory and subsequent immune response. During fetal and neonatal development programming of the HPAA, ANS and possibly the immune system is influenced by signals from the surrounding environment, as part of an adaptive mechanism to enhance the survival of the offspring. It is currently hypothesized that if this programming is either misguided, or the individual's environment is drastically altered such that neuroendocrine programming becomes maladaptive, it may contribute to the pathogenesis of certain diseases. Current research, suggests that exposure to inflammatory signals during critical windows of early life development may influence the programming of various genes within the neuroendocrine-immune axis. This review will provide, (1) an overview of the HPAA and ANS pathways that are activated during inflammation, highlighting studies that have used lipopolysaccharide as a model inflammagen and, (2) evidence to support the hypothesis that inflammatory stress during fetal and neonatal development can alter programming of the neuroendocrine-immune axis, influencing stress and immune responsiveness, and possibly disease resistance later in life.

Three weekly courses of betamethasone administered to pregnant baboons at 0.6, 0.65, and 0.7 of gestation alter fetal and maternal lymphocyte populations at 0.95 of gestation

The hypothalamic-pituitary-adrenal (HPA) axis plays a major role in the communication between the immune and neuroendocrine systems. Glucocorticoids are potent immunomodulatory hormones. In the present study, we evaluated the effect of three weekly courses of betamethasone, administered to pregnant baboons at 0.6, 0.65, and 0.7 of gestation, on maternal hematological parameters during treatment, maternal and fetal hematological parameters and lymphocyte populations at 0.95 of gestation, and fetal lymphoid organs and placental structure. Each weekly betamethasone course resulted in decreased granulocytes and increased lymphocytes and monocytes in maternal circulation (by percentage, p < 0.05). The percentage and absolute number of CD8+ T-cells in the maternal circulation were lower and CD4+ T-cells higher (p < 0.05) in treated pregnant animals at 0.95 gestation. The percentage of proliferating CD3- CD8+ cells was lower in blood obtained from the fetal heart of betamethasone-treated animals. In the betamethasone group, the number of CD8+ T-cells and NK cells were elevated and the number of T and CD4+ T-cells were reduced in fetal heart blood compared with the umbilical vein blood. The number of placental macrophages (CD68+ cells) per visual field in betamethasone-treated and control animals were not different. Taken together, our data show that betamethasone treatment of pregnant females with no indication of preterm labor affects some components of the fetal and maternal immune system, altering the maternal CD4+/CD8+ ratio and absolute number of fetal NK cell and maternal CD8+ T-cell.

Glucocorticoid programming

Epidemiological evidence suggests that an adverse fetal environment permanently programs physiology, leading to increased risks of cardiovascular, metabolic, and neuroendocrine disorders in adulthood. Prenatal glucocorticoid excess or stress might link fetal maturation and adult pathophysiology. In a variety of animal models, prenatal glucocorticoid exposure or inhibition of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), the fetoplacental "barrier" to maternal glucocorticoids, reduces birth weight and causes permanent hypertension, hyperglycemia, and increased hypothalamic-pituitary-adrenal axis (HPA) activity and behavior resembling anxiety. In humans, 11beta-HSD2 gene mutations cause low birth weight and reduced placental 11beta-HSD2 activity associated with intrauterine growth retardation. Low birth weight babies have higher plasma cortisol levels throughout adult life, indicating HPA programming. The molecular mechanisms may reflect permanent changes in the expression of specific transcription factors; key is the glucocorticoid receptor itself. Differential programming of the glucocorticoid receptor in different tissues reflects effects upon one or more of the multiple tissue-specific alternate first exons/promoters of the glucocorticoid receptor gene. Overall, the data suggest that either pharmacological or physiological exposure to excess glucocorticoids prenatally programs pathologies in adult life.

Cardiovascular and endocrine effects of a single course of maternal dexamethasone treatment in preterm fetal sheep

OBJECTIVE

To determine the effects of a single course of maternally administered dexamethasone on preterm fetal sheep in utero.

DESIGN

Prospective randomised controlled trial.

SETTING

University laboratory.

SAMPLE

Pregnant sheep at 0.7 of gestation.

METHODS

Pregnant ewes at 103 days of pregnancy (term = 147 days) were given two intramuscular injections of vehicle (n= 7) or 12 mg of dexamethasone (DEX; n= 8) 24 hours apart. Fetuses were continuously monitored for five days.

MAIN OUTCOME MEASURES

Fetal mean arterial blood pressure, carotid and femoral arterial blood flow and vascular resistance, heart rate, heart rate variability, fetal plasma cortisol and ACTH and fetal body movements.

RESULTS

DEX injections led to an acute increase in mean arterial blood pressure with a rise in carotid and femoral vascular resistance, a fall in femoral arterial blood flow, and a brief fall in fetal heart rate followed by significant tachycardia. From 24 hours after the injections, mean arterial blood pressure and vascular resistance returned to control values, however, a mild tachycardia [200 (3) vs 184 (4) bpm, P < 0.05] and loss of the circadian pattern of fetal heart rate variability persisted until the end of recording. Plasma ACTH and cortisol were markedly suppressed by DEX (P < 0.05), with values returning to control levels 32 and 72 hours after the first injection, respectively. There was no effect on basal fetal heart rate variability, body movements, carotid arterial blood flow, or the circadian pattern of fetal heart rate.

CONCLUSION

In contrast to previous experiments utilising direct fetal infusion of steroids, maternal administration of DEX was associated with only transient hypertension.

Treatment with immunosuppressive and anti-inflammatory agents delays onset of canine genetic narcolepsy and reduces symptom severity

All Doberman pinschers and Labrador retrievers homozygous for a mutation of the hypocretin (orexin) receptor-2 (hcrtr2) gene develop narcolepsy under normal conditions. Degenerative changes and increased display of major histocompatibility complex class II antigens have been linked to symptom onset in genetically narcoleptic Doberman pinschers. This suggests that the immune system may contribute to neurodegenerative changes and narcoleptic symptomatology in these dogs. We therefore attempted to alter the course of canine genetic narcolepsy, as an initial test of principle, by administering a combination of three immunosuppressive and anti-inflammatory drugs chosen to suppress the immune response globally. Experimental dogs were treated with a combination of methylprednisolone, methotrexate and azathioprine orally starting within 3 weeks after birth, and raised in an environment that minimized pathogen exposure. Symptoms in treated and untreated animals were quantified using the food elicited cataplexy test (FECT), modified FECT and actigraphy. With drug treatment, time to cataplexy onset more than doubled, time spent in cataplexy during tests was reduced by more than 90% and nighttime sleep periods were consolidated. Short-term drug administration to control dogs did not reduce cataplexy symptoms, demonstrating that the drug regimen did not directly affect symptoms. Treatment was stopped at 6 months, after which experimental animals remained less symptomatic than controls until at least 2 years of age. This treatment is the first shown to affect symptom development in animal or human genetic narcolepsy. Our findings show that hcrtr2 mutation is not sufficient for the full symptomatic development of canine genetic narcolepsy and suggest that the immune system may play a role in the development of this disorder.

Evidence for lower sympathetic nerve activity in young adults with low birth weight

OBJECTIVE

A dysfunction of the sympathetic nervous system may contribute to the development of hypertension and obesity in subjects with low birth weight (LBW). The present study examines resting sympathetic nerve traffic and its baroreflex modulation to the muscle vascular bed in healthy LBW subjects.

DESIGN

Case-control studies of 13 healthy LBW subjects (< 2500 g at term) aged 20-30 years and 13 normal birth weight subjects (NBW; 3200-3700 g) closely matched for age, gender and body mass index.

METHODS

Muscle sympathetic nerve activity (MSNA) recordings from the superficial peroneal nerve, blood pressure and heart rate were obtained at rest, during an inspiratory apnoea and a cold pressor test. Baroreflex function was evaluated by short-term infusion of nitroprusside and phenylephrine, respectively, in nine subjects of each group.

RESULTS

During resting conditions burst frequency was significantly lower in LBW subjects (LBW: 24.7 +/- 2.4; NBW: 34.4 +/- 2.1 bursts/min, P < 0.05). When normalized for the different baseline values, baroreflex-mediated changes in MSNA were similar in both groups. Maximal MSNA levels in response to inspiratory apnoea and the cold pressor test did not differ between the groups. Blood pressure and heart rate were similar in LBW and NBW subjects both at rest and during sympatho-excitatory manoeuvres.

CONCLUSIONS

Subjects born too small for their gestational age show a significantly lower sympathetic nerve activity under baseline conditions. Given the different baseline values, the sympathetic response to haemodynamic alteration is not affected in LBW subjects, and maximal activation during non-haemodynamic sympatho-excitatory manoeuvres is preserved.

Renal function in adult rats subjected to prenatal dexamethasone

1. Prenatal dexamethasone leads to low birth weight and compromises organogenesis, but its effects on nephrogenesis in male and female rats have not yet been investigated extensively. Reduced renal mass may be responsible for hypertension and renal haemodynamic and morphological adjustments to maintain the glomerular filtration rate (GFR). Subsequently, these compensatory mechanisms determine glomerular sclerosis and irreversible reduction in GFR. When a high-protein diet is associated with reduced renal mass, it accelerates glomerular sclerosis and the decline in renal function. The aim of the present study was to evaluate whether rats subjected to prenatal dexamethasone and a high-protein diet during growth present a premature decline in renal function. 2. The number of nephrons and renal haemodynamics were estimated in Wistar rats fed a high-protein diet (40% protein) after weaning in offspring of dams treated with either dexamethasone (0.1 mg/kg per day) or its vehicle (control; physiological solution, 0.1 mL/kg per day) during gestation. 3. At 70 days of age, rat offspring were anaesthetized and prepared surgically for renal haemodynamic measurements. 4. Mean arterial pressure (MAP), renal blood flow (RBF) and GFR were measured using a blood pressure transducer, a flow probe and inulin clearance, respectively. 5. The number of nephrons was counted using the acid-maceration technique. 6. Dexamethasone during pregnancy induced a lower weight gain in the dams (65%; P < 0.0001) and a lower birth weight in both male and female offspring (14 and 13%, respectively; P < 0.01). 7. Compared with control, the number of nephrons in male rats was reduced by 13% (30 703 +/- 1262 vs 26 308 +/- 1305, respectively; P < 0.05), but was unaltered in female rats (23 197 +/- 553 vs 24 231 +/- 1009, respectively). 8. Male and female rats did not show any alteration in MAP. In addition, they did not show any alteration in renal vascular resistance, RBF, filtration fraction or GFR. 9. In conclusion, prenatally administered dexamethasone (0.1 mg/kg during the entire pregnancy) induced a low birth weight. The magnitude of the reduction in nephrogenesis in male offspring from mothers treated with dexamethasone was not sufficient to alter renal function (measured at 70 days), even when rats had been fed a high-protein diet.

Glucocorticoid programming of the fetus; adult phenotypes and molecular mechanisms

It has been long recognised that the glucocorticoid administration to pregnant mammals (including humans) reduces offspring birth weight. Epidemiologically, low weight or thinness at birth is associated with an increased risk of cardiovascular and metabolic disorders in adult life. So, does fetal exposure to glucocorticoids produce such 'programming' of adult disorders? Here data are reviewed which show, in rodents and other model species, that antenatal exposure to glucocorticoids reduces offspring birth weight and produces permanent hypertension, hyperglycaemia, hyperinsulinaemia, altered behaviour and neuroendocrine responses throughout the lifespan. This occurs with exogenous (dexamethasone) or endogenous glucocorticoids, the latter achieved by inhibiting 11 beta-hydroxysteroid dehydrogenase type 2, the feto-placental enzymic barrier to maternal glucocorticoids. Processes underlying fetal programming include determination of the 'set point' of the hypothalamic-pituitary-adrenal axis and of tissue glucocorticoid receptor expression. Detailed molecular mechanisms are being dissected. Analogous stress axis hyperreactivity occurs in lower birth weight humans and may be an early manifestation and indicate approaches to manipulation or prevention of the phenotype.

Neonatal glucocorticoids and the developing brain: short-term treatment with life-long consequences?

Although synthetic glucocorticoids are frequently used in hospital for the prevention of chronic lung disease in premature infants, major concern has arisen about the possible long-term consequences of these treatments. Animal research provides evidence for the idea that neonatal glucocorticoid treatment enhances susceptibility to autoimmune disease in adult life. Altered functioning of the hypothalamo-pituitary-adrenal axis, and/or changes at higher brain levels might underlie alterations in disease susceptibility.

Glucocorticoid programming of pituitary-adrenal function: mechanisms and physiological consequences

Increasing epidemiological evidence supports the notion that adverse events in fetal life permanently alter the structure and physiology of the adult offspring, a phenomenon dubbed 'fetal programming'. In particular, low weight or thinness at birth in humans is associated with an increased risk of cardiovascular and metabolic disorders as well as neuroendocrine dysfunction in adult life. Glucocorticoid administration during pregnancy is well-documented to both reduce offspring birth weight and alter the maturation of organs (hence their use to accelerate fetal lung maturation in premature labour). Here data are reviewed which show, in rodents and other models, that antenatal exposure to endogenous or exogenous glucocorticoids reduces offspring birth weight and produces permanent hypertension, hyperglycaemia, hyperinsulinaemia, altered behaviour and neuroendocrine responses throughout the lifespan. Processes underlying fetal programming include determination of the 'set point' of the hypothalamic-pituitary-adrenal (HPA) axis and of tissue glucocorticoid receptor (GR) expression. Similar HPA axis hyperreactivity occurs in lower birth weight humans and may be an early manifestation of the 'low birth weight' phenotype.

Ontogenetic aspects of hypertension development: analysis in the rat

In this review, we attempt to outline the age-dependent interactions of principal systems controlling the structure and function of the cardiovascular system in immature rats developing hypertension. We focus our attention on the cardiovascular effects of various pharmacological, nutritional, and behavioral interventions applied at different stages of ontogeny. Several distinct critical periods (developmental windows), in which particular stimuli affect the further development of the cardiovascular phenotype, are specified in the rat. It is evident that short-term transient treatment of genetically hypertensive rats with certain antihypertensive drugs in prepuberty and puberty (at the age of 4-10 wk) has long-term beneficial effects on further development of their cardiovascular apparatus. This juvenile critical period coincides with the period of high susceptibility to the hypertensive effects of increased salt intake. If the hypertensive process develops after this critical period (due to early antihypertensive treatment or late administration of certain hypertensive stimuli, e.g., high salt intake), blood pressure elevation, cardiovascular hypertrophy, connective tissue accumulation, and end-organ damage are considerably attenuated compared with rats developing hypertension during the juvenile critical period. As far as the role of various electrolytes in blood pressure modulation is concerned, prohypertensive effects of dietary Na+ and antihypertensive effects of dietary Ca2+ are enhanced in immature animals, whereas vascular protective and antihypertensive effects of dietary K+ are almost independent of age. At a given level of dietary electrolyte intake, the balance between dietary carbohydrate and fat intake can modify blood pressure even in rats with established hypertension, but dietary protein intake affects the blood pressure development in immature animals only. Dietary protein restriction during gestation, as well as altered mother-offspring interactions in the suckling period, might have important long-term hypertensive consequences. The critical periods (developmental windows) should be respected in the future pharmacological or gene therapy of human hypertension.

Altered immune function in human newborns after prenatal administration of betamethasone: enhanced natural killer cell activity and decreased T cell proliferation in cord blood

During the course of human pregnancy, glucocorticoid (GC) treatment is given when preterm delivery is expected. This treatment is successful in stimulating the development of the fetal lung. However, in animal studies, a number of side effects of perinatal GC treatment have been described. The aim of the present study was to evaluate in humans the effects of antenatal GC treatment on development of the immune system. In addition, we examined the development of immune reactivity in infants born preterm and at term who did not receive GC treatment antenatally. We tested mitogen-induced T cell proliferation, natural killer cell activity, and lipopolysaccharide-induced IL-6 production in cord blood samples. We found that there is a significant effect of gestational age on the capacity of T cells to proliferate and of natural killer cells to kill K562 tumor cells. The capacity to produce IL-6 does not change between gestational age 26 and 41 wk. Moreover, our results show that antenatal treatment with GC does have immunomodulatory effects: T cell proliferation is decreased in infants born very preterm (gestational age 26-31 wk) as well as in infants born between 32 and 36 wk of gestation. In contrast, the activity of natural killer cells is only increased in GC-treated infants born between 26 and 31 wk. We did not observe a significant effect of antenatal GC treatment on the capacity to produce IL-6.

Glucocorticoids, feto-placental 11 beta-hydroxysteroid dehydrogenase type 2, and the early life origins of adult disease

Increasing human epidemiological data suggest that events that subtly retard intrauterine growth may determine common disorders, such as hypertension and non-insulin-dependent diabetes, in adult life. The underlying mechanisms are unknown. However, excessive fetal exposure to glucocorticoids retards growth and "programs" adult hypertension in rats. 11 beta-Hydroxysteroid dehydrogenase type 2 (11 beta-HSD2) catalyzes the rapid inactivation of cortisol and corticosterone to inert 11 keto-products. Normally, 11 beta-HSD2 in the placenta and some fetal tissues is thought to protect the fetus from excess maternal glucocorticoids. In both rats and humans there is considerable natural variation in placental 11 beta-HSD2, and enzyme activity correlates with birth weight. Moreover, inhibition of feto-placental 11 beta-HSD2 in the rat reduces birth weight and produces hypertensive and hyperglycaemic adult offspring, many months after prenatal treatment; effects are dependent upon intact maternal adrenals, suggesting a direct action on the fetus or placenta. Maternal protein restriction during pregnancy also produces hypertensive offspring and selectively attenuates placental 11 beta-HSD2 activity. These data suggest that feto-placental 11 beta-HSD2, by regulating fetal exposure to maternal glucocorticoids, crucially determines fetal growth and the programming of later disorders. Deficiency of the barrier to maternal glucocorticoids may represent a common pathway between the maternal environment and feto-placental programming of later disease. These data may, at least in part, explain the human observations linking early life events to the risk of subsequent disease.

Inhibition of 11-beta-hydroxysteroid dehydrogenase in pregnant rats and the programming of blood pressure in the offspring

Recent epidemiological studies have linked low birth weight with the later occurrence of cardiovascular and metabolic disorders, particularly hypertension. We have proposed that fetal exposure to excess maternal glucocorticoids may underpin this association. Normally, the fetus is protected from maternal glucocorticoids by placental 11beta-hydroxysteroid dehydrogenase (11beta-HSD). We have previously shown that treatment of pregnant rats with dexamethasone, a synthetic glucocorticoid that is poorly metabolized by the enzyme, reduces birth weight and produces elevated blood pressure in the adult offspring. Moreover, low activity of placental 11beta-HSD correlates with low birth weight in rats. Here, we show that maternal administration of carbenoxolone, a potent inhibitor of 11 beta-HSD, throughout pregnancy leads to reduced birth weight (mean 20 percent decrease) and elevated blood pressures (increase in mean arterial pressure, 9 mm Hg in males, 7 mm Hg in females) in the adult offspring of carbenoxolone-treated rats. This effect requires the presence of maternal adrenal products, as carbenoxolone given to adrenalectomized pregnant rats had no effect on birth weight or blood pressure. These data support the hypothesis that excess exposure of the fetoplacental unit to maternal glucocorticoids reduces birth weight and programs subsequent hypertension and indicate a key role for placental 11beta-HSD in controlling such exposure.

Programming of brainstem serotonin transporter development by prenatal glucocorticoids

Prenatal stress or exposure to excess glucocorticoids are known to alter central nervous system function and to result in lasting changes in reactions to stress. The potential involvement of specific elements of brainstem serotonergic neurons was examined in the current study. Pregnant rats were given 0.05, 0.2 or 0.8 mg/kg of dexamethasone on gestational days 17, 18 and 19, and the effects on development of the serotonin presynaptic transporter were assessed from birth to young adulthood by measurement of [3H]paroxetine binding to membrane preparations. Dexamethasone produced a dose-dependent retardation of body and brainstem growth but evoked a significant elevation of [3H]paroxetine binding that persisted into adulthood. Effects on [3H]paroxetine binding were robust even at the lowest dose, which did not suppress growth, indicating that the programming of this transporter is more sensitive to glucocorticoids than is general development. At the highest dose, promotional effects on serotonin transporter expression were offset by impaired growth, so that the peak effect was seen at the intermediate dose of dexamethasone. There were no comparable effects on serotonin transmitter levels, indicating selectivity toward promotion of transporter expression as distinct from simply increasing the number of serotonergic nerve terminals or all nerve terminal components. As the effect of prenatal dexamethasone treatment on the serotonin transporter is more persistent than those on other monoamine transporters, and is not shared by postnatal treatment or by treatment in adulthood, it likely represents specific programming by glucocorticoids during the prenatal period. Aberrant serotonergic transporter expression may contribute to alterations of synaptic function that ultimately produce the physiological abnormalities seen after prenatal stress or glucocorticoid treatment.

Effects of short-term dexamethasone treatment during pregnancy on the development of the immune system and the hypothalamo-pituitary adrenal axis in the rat

The effects of glucocorticoid (GC) treatment on the mature immune and neuroendocrine system are known to be reversible. However, prenatal GC exposure may have irreversible consequences on the development of the newborn. In this study, possible long-lasting effects of short-term prenatal GC treatment were examined on the developing thymus, spleen and hypothalamo-pituitary adrenal axis (HPA axis). Female rats were given dexamethasone (DEX, 400 micrograms, i.p.) on day 17 and 19 of pregnancy and offspring was studied at several time intervals (1-20 days) after birth, for examination of thymus, spleen, hypothalamus and blood plasma. Examination of thymus and spleen revealed that prenatal exposure to DEX resulted in decreased T cell numbers in thymus and spleen on day 1 after birth. Thymus regeneration after DEX exposure both during pregnancy and in adult life was completed after 24 days. However, the kinetics of regeneration of the thymi after prenatal DEX exposure were different from that seen after DEX in adult life. Whereas DEX treatment during pregnancy resulted in an increased ratio of CD4+/CD8- thymocytes over CD4-/CD8+ thymocytes compared to control groups on day 7 and day 20 after birth (time X treatment interaction; P < 0.05), DEX treatment in adult life did not change this ratio. T cell numbers in the spleen were significantly decreased at all neonatal ages studied. Regarding the hypothalamus, prenatal exposure to DEX altered the pattern of neonatal changes in peptide expression in corticotropin-releasing hormone neurons, with a selective reduction in CRH storage in the median eminence (7 and 9 days after birth) and an increase in AVP storage (9 and 20 days after birth). The ratio of AVP over CRH was significantly increased at all developmental ages studied. No effects were seen on basal ACTH and corticosterone levels in plasma. In conclusion, the kinetics of thymus regeneration after DEX exposure during pregnancy were different from that seen after DEX exposure in adult life. Prenatal DEX exposure also seemed to delay the migration of T cells into the spleen. Furthermore, prenatal DEX treatment exerted major effects on hypothalamic CRH neurons that maintained for at least 20 days after birth, which points towards an enhanced stress responsiveness of the HPA axis in later life.

Placental 11 beta-hydroxysteroid dehydrogenase and the programming of hypertension

Excessive foetal exposure to glucocorticoids retards growth and "programmes" adult hypertension in rats. Placental 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which catalyses the conversion of corticosterone and cortisol to inert 11 keto-products, normally protects the foetus from excess maternal glucocorticoids. In both rats and humans there is considerable natural variation in placental 11 beta-HSD, and enzyme activity correlates with birth weight. Moreover, inhibition of placental 11 beta-HSD in the rat reduces birth weight and produces hypertensive adult offspring, many months after prenatal treatment with enzyme inhibitors; these effects are dependent upon maternal adrenal products. These data suggest that placental 11 beta-HSD, by regulating foetal exposure to maternal glucocorticoids, crucially determines foeto-placental growth and the programming of hypertension. Maternal protein restriction during pregnancy also produces hypertensive offspring and selectively attenuates placental 11 beta-HSD activity. Thus, deficiency of the placental barrier to maternal glucocorticoids may represent a common pathway between the maternal environment and foeto-placental programming of later disease. These data may, at least in part, explain the human epidemiological observations linking early life events to the risk of subsequent hypertension. The recent characterization, purification and cDNA cloning of a distinct human placental 11 beta-HSD (type 2) will aid the further study of these intriguing findings.