Nicotinamide Riboside, an NAD + Precursor, Protects Against Cardiac Mitochondrial Dysfunction in Fetal Guinea Pigs Exposed to Gestational Hypoxia

Gestational hypoxia inhibits mitochondrial function in the fetal heart and placenta contributing to fetal growth restriction and organ dysfunction. NAD + deficiency may contribute to a metabolic deficit by inhibiting oxidative phosphorylation and ATP synthesis. We tested the effects of nicotinamide riboside (NR), an NAD + precursor, as a treatment for reversing known mitochondrial dysfunction in hypoxic fetal hearts. Pregnant guinea pigs were housed in room air (normoxia) or placed in a hypoxic chamber (10.5%O2) for the last 14 days of gestation (term = 65 days) and administered either water or NR (1.6 mg/ml) in the drinking bottle. Fetuses were excised at term, and NAD + levels of maternal liver, placenta, and fetal heart ventricles were measured. Indices of mitochondrial function (complex IV activity, sirtuin 3 activity, protein acetylation) and ATP synthesis were measured in fetal heart ventricles of NR-treated/untreated normoxic and hypoxic animals. Hypoxia reduced fetal body weight in both sexes (p = 0.01), which was prevented by NR. Hypoxia had no effect on maternal liver NAD + levels but decreased (p = 0.04) placenta NAD + levels, the latter normalized with NR treatment. Hypoxia had no effect on fetal heart NAD + but decreased (p < 0.05) mitochondrial complex IV and sirtuin 3 activities, ATP content, and increased mitochondrial acetylation, which were all normalized with maternal NR. Hypoxia increased (p < 0.05) mitochondrial acetylation in female fetal hearts but had no effect on other mitochondrial indices. We conclude that maternal NR is an effective treatment for normalizing mitochondrial dysfunction and ATP synthesis in the hypoxic fetal heart.

The Prenatal Hypoxic Pathology Associated with Maternal Stress Predisposes to Dysregulated Expression of the chrna7 Gene and the Subsequent Development of Nicotine Addiction in Adult Offspring

INTRODUCTION

Previous studies have shown that fetal hypoxia predisposes individuals to develop addictive disorders in adulthood. However, the specific impact of maternal stress, mediated through glucocorticoids and often coexisting with fetal hypoxia, is not yet fully comprehended.

METHODS

To delineate the potential effects of these pathological factors, we designed models of prenatal severe hypoxia (PSH) in conjunction with maternal stress and prenatal intrauterine ischemia (PII). We assessed the suitability of these models for our research objectives by measuring HIF1α levels and evaluating the glucocorticoid neuroendocrine system. To ascertain nicotine dependence, we employed the conditioned place aversion test and the startle response test. To identify the key factor implicated in nicotine addiction associated with PSH, we employed techniques such as Western blot, immunohistochemistry, and correlational analysis between chrna7 and nr3c1 genes across different brain structures.

RESULTS

In adult rats exposed to PSH and PII, we observed increased levels of HIF1α in the hippocampus (HPC). However, the PSH group alone exhibited reduced glucocorticoid receptor levels and disturbed circadian glucocorticoid rhythms. Additionally, they displayed signs of nicotine addiction in the conditioned place aversion and startle response tests. We also observed elevated levels of phosphorylated DARPP-32 protein in the nucleus accumbens (NAc) indicated compromised glutamatergic efferent signaling. Furthermore, there was reduced expression of α7 nAChR, which modulates glutamate release, in the medial prefrontal cortex (PFC) and HPC. Correlation analysis revealed strong associations between chrna7 and nr3c1 expression in both brain structures.

CONCLUSION

Perturbations in the glucocorticoid neuroendocrine system and glucocorticoid-dependent gene expression of chrna7 associated with maternal stress response to hypoxia in prenatal period favor the development of nicotine addiction in adulthood.

Effects of Gestational Hypoxia on PGC1α and Mitochondrial Acetylation in Fetal Guinea Pig Hearts

Chronic intrauterine hypoxia is a significant pregnancy complication impacting fetal heart growth, metabolism, and mitochondrial function, contributing to cardiovascular programming of the offspring. PGC1α (peroxisome proliferator-activated receptor γ co-activator 1α) is the master regulator of mitochondrial biogenesis. We investigated the effects of hypoxia on PGC1α expression following exposure at different gestational ages. Time-mated pregnant guinea pigs were exposed to normoxia (NMX, 21% O2) or hypoxia (HPX, 10.5% O2) at either 25-day (early-onset) or 50-day (late-onset) gestation, and all fetuses were extracted at term (term = ~65-day gestation). Expression of nuclear PGC1α, sirtuin 1 (SIRT1), AMP-activated protein kinase (AMPK), and mitochondrial sirtuin 3 (SIRT3) was measured, along with SIRT3 activity and mitochondrial acetylation of heart ventricles of male and female fetuses. Early-onset hypoxia increased (P<0.05) fetal cardiac nuclear PGC1α and had no effect on mitochondrial acetylation of either growth-restricted males or females. Late-onset hypoxia had either no effect or decreased (P<0.05) PCC1α expression in males and females, respectively, but increased (P<0.05) mitochondrial acetylation in both sexes. Hypoxia had variable effects on expression of SIRT1, AMPK, SIRT3, and SIRT3 activity depending on the sex. The capacity of the fetal heart to respond to hypoxia differs depending on the gestational age of exposure and sex of the fetus. Further, the effects of late-onset hypoxia on fetal heart function impose a greater risk to male than female fetuses, which has implications toward cardiovascular programming effects of the offspring.

Tissue-specific responses that constrain glucose oxidation and increase lactate production with the severity of hypoxemia in fetal sheep

Fetal hypoxemia decreases insulin and increases cortisol and norepinephrine concentrations and may restrict growth by decreasing glucose utilization and altering substrate oxidation. Specifically, we hypothesized that hypoxemia would decrease fetal glucose oxidation and increase lactate and pyruvate production. We tested this by measuring whole body glucose oxidation and lactate production, and molecular pathways in liver, muscle, adipose, and pancreas tissues of fetuses exposed to maternal hypoxemia for 9 days (HOX) compared with control fetal sheep (CON) in late gestation. Fetuses with more severe hypoxemia had lower whole body glucose oxidation rates, and HOX fetuses had increased lactate production from glucose. In muscle and adipose tissue, expression of the glucose transporter GLUT4 was decreased. In muscle, pyruvate kinase (PKM) and lactate dehydrogenase B (LDHB) expression was decreased. In adipose tissue, LDHA and lactate transporter (MCT1) expression was increased. In liver, there was decreased gene expression of PKLR and MPC2 and phosphorylation of PDH, and increased LDHA gene and LDH protein abundance. LDH activity, however, was decreased only in HOX skeletal muscle. There were no differences in basal insulin signaling across tissues, nor differences in pancreatic tissue insulin content, β-cell area, or genes regulating β-cell function. Collectively, these results demonstrate coordinated metabolic responses across tissues in the hypoxemic fetus that limit glucose oxidation and increase lactate and pyruvate production. These responses may be mediated by hypoxemia-induced endocrine responses including increased norepinephrine and cortisol, which inhibit pancreatic insulin secretion resulting in lower insulin concentrations and decreased stimulation of glucose utilization.NEW & NOTEWORTHY Hypoxemia lowered fetal glucose oxidation rates, based on severity of hypoxemia, and increased lactate production. This was supported by tissue-specific metabolic responses that may result from increased norepinephrine and cortisol concentrations, which decrease pancreatic insulin secretion and insulin concentrations and decrease glucose utilization. This highlights the vulnerability of metabolic pathways in the fetus and demonstrates that constrained glucose oxidation may represent an early event in response to sustained hypoxemia and fetal growth restriction.

Chronic Hypoxia Inhibits Respiratory Complex IV Activity and Disrupts Mitochondrial Dynamics in the Fetal Guinea Pig Forebrain

Mitochondrial dysfunction is an underlying cause of childhood neurological disease secondary to the crucial role of mitochondria in proper neurodevelopment. We hypothesized that chronic intrauterine hypoxia (HPX) induces mitochondrial deficits by altering mitochondrial biogenesis and dynamics in the fetal brain. Pregnant guinea pigs were exposed to either normoxia (NMX, 21%O2) or HPX (10.5%O2) starting at 28-day (early onset, EO-HPX) or 50-day (late onset, LO-HPX) gestation until term (65 days). Near-term male and female fetuses were extracted from anesthetized sows, and mitochondria were isolated from excised fetal forebrains (n = 6/group). Expression of mitochondrial complex subunits I-V (CI-CV), fission (Drp-1), and fusion (Mfn-2) proteins was measured by Western blot. CI and CIV enzyme activities were measured by colorimetric assays. Chronic HPX reduced fetal body wts and increased (P < 0.05) brain/body wt ratios of both sexes. CV subunit levels were increased in EO-HPX males only and CII levels increased in LO-HPX females only compared to NMX. Both EO- and LO-HPX decreased CIV activity in both sexes but had no effect on CI activity. EO-HPX increased Drp1 and decreased Mfn2 levels in males, while LO-HPX had no effect on either protein levels. In females, both EO-HPX and LO-HPX increased Drp1 but had no effect on Mfn2 levels. Chronic HPX alters abundance and activity of select complex subunits and shifts mitochondrial dynamics toward fission in a sex-dependent manner in the fetal guinea pig brain. This may be an underlying mechanism of reduced respiratory efficiency leading to disrupted metabolism and increased vulnerability to a second neurological injury at the time of birth in HPX fetal brains.

Hypoxia-induced inhibition of mTORC1 activity in the developing lung: a possible mechanism for the developmental programming of pulmonary hypertension

Perinatal hypoxia induces permanent structural and functional changes in the lung and its pulmonary circulation that are associated with the development of pulmonary hypertension (PH) in later life. The mechanistic target of the rapamycin (mTOR) pathway is vital for fetal lung development and is implicated in hypoxia-associated PH, yet its involvement in the developmental programming of PH remains unclear. Pregnant C57/BL6 dams were placed in hyperbaric (760 mmHg) or hypobaric chambers during gestation (505 mmHg, day 15 through postnatal day 4) or from weaning through adulthood (420 mmHg, postnatal day 21 through 8 wk). Pulmonary hemodynamics and right ventricular systolic pressure (RVSP) were measured at 8 wk. mTOR pathway proteins were assessed in fetal (day 18.5) and adult lung (8 wk). Perinatal hypoxia induced PH during adulthood, even in the absence of a sustained secondary hypoxic exposure, as indicated by reduced pulmonary artery acceleration time (PAAT) and peak flow velocity through the pulmonary valve, as well as greater RVSP, right ventricular (RV) wall thickness, and RV/left ventricular (LV) weight. Such effects were independent of increased blood viscosity. In fetal lung homogenates, hypoxia reduced the expression of critical downstream mTOR targets, most prominently total and phosphorylated translation repressor protein (4EBP1), as well as vascular endothelial growth factor, a central regulator of angiogenesis in the fetal lung. In contrast, adult offspring of hypoxic dams tended to have elevated p4EBP1 compared with controls. Our data suggest that inhibition of mTORC1 activity in the fetal lung as a result of gestational hypoxia may interrupt pulmonary vascular development and thereby contribute to the developmental programming of PH.NEW & NOTEWORTHY We describe the first study to evaluate a role for the mTOR pathway in the developmental programming of pulmonary hypertension. Our findings suggest that gestational hypoxia impairs mTORC1 activation in the fetal lung and may impede pulmonary vascular development, setting the stage for pulmonary vascular disease in later life.

Late-Pregnancy Fetal Hypoxia Is Associated With Altered Glucose Metabolism and Adiposity in Young Adult Offspring of Women With Type 1 Diabetes

OBJECTIVE

To investigate associations between exposure to fetal hypoxia and indicators of metabolic health in young adult offspring of women with type 1 diabetes (OT1D).

METHODS

156 OT1D born between 7/1995 and 12/2000 at Helsinki University Hospital, Finland, were invited for follow-up between 3/2019 and 11/2019. A control group of 442 adults born from non-diabetic pregnancies, matched for date and place of birth, was obtained from the Finnish Medical Birth Register. In total, 58 OT1D and 86 controls agreed to participate. All OT1D had amniotic fluid (AF) sampled for erythropoietin (EPO) measurement within two days before delivery in order to diagnose fetal hypoxia. In total, 29 OTID had an AF EPO concentration <14.0 mU/l, defined as normal, and were categorized into the low EPO (L-EPO) group. The remaining 29 OT1D had AF EPO ≥14.0 mU/ml, defined as fetal hypoxia, and were categorized into the high EPO (H-EPO) group. At the age of 18-23 years, participants underwent a 2-h 75g oral glucose tolerance test (OGTT) in addition to height, weight, waist circumference, body composition, blood pressure, HbA_1c, cholesterol, triglyceride, high-sensitivity CRP and leisure-time physical activity measurements.

RESULTS

Two OT1D were diagnosed with diabetes and excluded from further analyses. At young adult age, OT1D in the H-EPO group had a higher BMI than those in the L-EPO group. In addition, among female participants, waist circumference and body fat percentage were highest in the H-EPO group. In the OGTTs, the mean (SD) 2-h post-load plasma glucose (mmol/L) was higher in the H-EPO [6.50 (2.11)] than in the L-EPO [5.21 (1.10)] or control [5.67 (1.48)] offspring (p=0.009). AF EPO concentrations correlated positively with 2-h post-load plasma glucose [r=0.35 (95% CI: 0.07 to 0.62)] and serum insulin [r=0.44 (95% CI: 0.14 to 0.69)] concentrations, even after adjusting for maternal BMI, birth weight z-score, gestational age at birth and adult BMI. Control, L-EPO and H-EPO groups did not differ with regards to other assessed parameters.

CONCLUSIONS

High AF EPO concentrations in late pregnancy, indicating fetal hypoxia, are associated with increased adiposity and elevated post-load glucose and insulin concentrations in young adult OT1D.

Impact of Chronic Fetal Hypoxia and Inflammation on Cardiac Pacemaker Cell Development

Chronic fetal hypoxia and infection are examples of adverse conditions during complicated pregnancy, which impact cardiac myogenesis and increase the lifetime risk of heart disease. However, the effects that chronic hypoxic or inflammatory environments exert on cardiac pacemaker cells are poorly understood. Here, we review the current evidence and novel avenues of bench-to-bed research in this field of perinatal cardiogenesis as well as its translational significance for early detection of future risk for cardiovascular disease.

Chronic fetal hypoxia disrupts the peri-conceptual environment in next-generation adult female rats

KEY POINTS

Exposure to chronic hypoxia during gestation influences long-term health and development, including reproductive capacity, across generations. If the peri-conceptual environment in the developing oviduct is affected by gestational hypoxia, then this could have implications for later fertility and the health of future generations. In the present study, we show that the oviducts of female rats exposed to chronic hypoxia in utero have reduced telomere length, decreased mitochondrial DNA biogenesis and increased oxidative stress The results of the present study show that exposure to chronic gestational hypoxia leads to accelerated ageing of the oviduct in early adulthood and they help us understand how exposure to hypoxia during development could influence reproductive health across generations.

ABSTRACT

Exposure to chronic hypoxia during fetal development has important effects on immediate and long-term outcomes in offspring. Adverse impacts in adult offspring include impairment of cardiovascular function, metabolic derangement and accelerated ovarian ageing. However, it is not known whether other aspects of the female reproductive system may be similarly affected. In the present study, we examined the impact of chronic gestational hypoxia on the developing oviduct. Wistar rat dams were randomized to either normoxia (21%) or hypoxia (13%) from day 6 post-mating until delivery. Post-delivery female offspring were maintained in normoxia until 4 months of age. Oviductal gene expression was assayed at the RNA (quantitative RT-PCR) and protein (western blotting) levels. Oviductal telomere length was assayed using Southern blotting. Oviductal telomere length was reduced in the gestational hypoxia-exposed animals compared to normoxic controls (P < 0.01). This was associated with a specific post-transcriptional reduction in the KU70 subunit of DNA-pk in the gestational hypoxia-exposed group (P < 0.05). Gestational hypoxia-exposed oviducts also showed evidence of decreased mitochondrial DNA biogenesis, reduced mtDNA copy number (P < 0.05) and reduced gene expression of Tfam (P < 0.05) and Pgc1α (P < 0.05). In the hypoxia-exposed oviducts, there was upregulation of mitochondrial-specific anti-oxidant defence enzymes (MnSOD; P < 0.01). Exposure to chronic gestational hypoxia leads to accelerated ageing of the oviduct in adulthood. The oviduct plays a central role in early development as the site of gamete transport, syngamy, and early development; hence, accelerated ageing of the oviductal environment could have important implications for fertility and the health of future generations.

Intervention against hypertension in the next generation programmed by developmental hypoxia

Evidence derived from human clinical studies and experimental animal models shows a causal relationship between adverse pregnancy and increased cardiovascular disease in the adult offspring. However, translational studies isolating mechanisms to design intervention are lacking. Sheep and humans share similar precocial developmental milestones in cardiovascular anatomy and physiology. We tested the hypothesis in sheep that maternal treatment with antioxidants protects against fetal growth restriction and programmed hypertension in adulthood in gestation complicated by chronic fetal hypoxia, the most common adverse consequence in human pregnancy. Using bespoke isobaric chambers, chronically catheterized sheep carrying singletons underwent normoxia or hypoxia (10% oxygen [O2]) ± vitamin C treatment (maternal 200 mg.kg-1 IV daily) for the last third of gestation. In one cohort, the maternal arterial blood gas status, the value at which 50% of the maternal hemoglobin is saturated with oxygen (P50), nitric oxide (NO) bioavailability, oxidative stress, and antioxidant capacity were determined. In another, naturally delivered offspring were raised under normoxia until early adulthood (9 months). Lambs were chronically instrumented and cardiovascular function tested in vivo. Following euthanasia, femoral arterial segments were isolated and endothelial function determined by wire myography. Hypoxic pregnancy induced fetal growth restriction and fetal oxidative stress. At adulthood, it programmed hypertension by enhancing vasoconstrictor reactivity and impairing NO-independent endothelial function. Maternal vitamin C in hypoxic pregnancy improved transplacental oxygenation and enhanced fetal antioxidant capacity while increasing NO bioavailability, offsetting constrictor hyper-reactivity and replenishing endothelial function in the adult offspring. These discoveries provide novel insight into mechanisms and interventions against fetal growth restriction and adult-onset programmed hypertension in an animal model of complicated pregnancy in a species of similar temporal developmental milestones to humans.

Chronically Hypoxic Fetal Lambs Supported by an Extra-Uterine Device Exhibit Mitochondrial Dysfunction and Elevations of Hypoxia Inducible Factor 1-Alpha

INTRODUCTION

We have recently developed an extra-uterine environment for neonatal development (EXTEND) capable of supporting premature fetal lambs and have been able to replicate hypoxic in utero conditions by controlling fetal oxygen delivery. In this study, we investigated the fetal mitochondrial response to hypoxia.

METHODS

Eight premature fetal lambs were delivered via hysterotomy and transitioned to extra-uterine support for 3 weeks. The lambs were divided into 2 groups: normoxic fetuses which maintained physiologic oxygen delivery and hypoxic fetuses in which oxygen delivery was significantly reduced. Control fetuses were delivered via hysterotomy but not cannulated. Measurements of mitochondrial membrane potential (MMP) were performed in peripheral blood mononuclear cells.

RESULTS

There were no significant differences in MMP between normoxic EXTEND fetuses and controls. Hypoxic fetuses had significantly more depolarized mitochondria compared to normoxic fetuses overall, and these changes were specifically appreciated in weeks 1 and 2, but not by week 3. Hypoxic fetuses had significantly elevated levels of HIF-1α compared to normoxic fetuses in the first 2 weeks.

DISCUSSION

Normoxic fetal lambs supported by EXTEND demonstrate normal mitochondrial function as evidenced by equivalent membrane potentials compared to control fetuses. Hypoxic fetuses exhibit mitochondrial dysfunction, though they do show evidence of adaptation after 3 weeks of hypoxic exposure.

Prenatal Hypoxia Induced Dysfunction in Cerebral Arteries of Offspring Rats

Background

Hypoxia during pregnancy could cause abnormal development and lead to increased risks of vascular diseases in adults. This study determined angiotensin II (AII)‐mediated vascular dysfunction in offspring middle cerebral arteries (MCA).

Methods and Results

Pregnant rats were subjected to hypoxia. Vascular tension in offspring MCA by AII with or without inhibitors, calcium channel activities, and endoplasmic reticulum calcium stores were tested. Whole‐cell patch clamping was used to investigate voltage‐dependent calcium channel currents. mRNA expression was tested using quantitative real‐time polymerase chain reaction. AII‐mediated MCA constriction was greater in male offspring exposed to prenatal hypoxia. AT1 and AT2 receptors were involved in the altered AII‐mediated vasoconstriction. Prenatal hypoxia increased baseline activities of L‐type calcium channel currents in MCA smooth muscle cells. However, calcium currents stimulated by AII were not significantly changed, whereas nifedipine inhibited AII‐mediated vasoconstrictions in the MCA. Activities of IP₃/ryanodine receptor–operated calcium channels, endoplasmic reticulum calcium stores, and sarcoendoplasmic reticulum membrane Ca²⁺‐ATPase were increased. Prenatal hypoxia also caused dysfunction of vasodilatation via the endothelium NO synthase. The mRNA expressions of AT1A, AT1B, AT2R, Cav1.2α1C, Cav3.2α1H, and ryanodine receptor RyR2 were increased in the prenatal‐hypoxia group.

Conclusions

Hypoxia in pregnancy could induce dysfunction in both contraction and dilation in the offspring MCA. AII‐increased constriction in the prenatal‐hypoxia group was not mainly dependent on the L‐type and T‐type calcium channels; it might predominantly rely on the AII receptors, IP₃/ryanodine receptors, and the endoplasmic reticulum calcium store as well as calcium ATPase.

Maternal chronic hypoxia increases expression of genes regulating lung liquid movement and surfactant maturation in male fetuses in late gestation

KEY POINTS

Chronic fetal hypoxaemia is a common pregnancy complication associated with intrauterine growth restriction that may influence respiratory outcome at birth. We investigated the effect of maternal chronic hypoxia for a month in late gestation on signalling pathways regulating fetal lung maturation and the transition to air-breathing at birth using isobaric hypoxic chambers without alterations to maternal food intake. Maternal chronic hypoxia in late gestation increases fetal lung expression of genes regulating hypoxia signalling, lung liquid reabsorption and surfactant maturation, which may be an adaptive response in preparation for the successful transition to air-breathing at birth. In contrast to other models of chronic fetal hypoxaemia, late gestation onset fetal hypoxaemia promotes molecular regulation of fetal lung maturation. This suggests a differential effect of timing and duration of fetal chronic hypoxaemia on fetal lung maturation, which supports the heterogeneity observed in respiratory outcomes in newborns following exposure to chronic hypoxaemia in utero.

ABSTRACT

Chronic fetal hypoxaemia is a common pregnancy complication that may arise from maternal, placental and/or fetal factors. Respiratory outcome of the infant at birth likely depends on the duration, timing and severity of the hypoxaemic insult. We have isolated the effect of maternal chronic hypoxia (MCH) for a month in late gestation on fetal lung development. Pregnant ewes were exposed to normoxia (21% O2 ) or hypoxia (10% O2 ) from 105 to 138 days of gestation (term ∼145 days). At 138 days, gene expression in fetal lung tissue was determined by quantitative RT-PCR. Cortisol concentrations were determined in fetal plasma and lung tissue. Numerical density of surfactant protein positive cells was determined by immunohistochemistry. MCH reduced maternal PaO2 (106 ± 2.9 vs. 47 ± 2.8 mmHg) and fetal body weight (4.0 ± 0.4 vs. 3.2 ± 0.9 kg). MCH increased fetal lung expression of the anti-oxidant marker CAT and decreased expression of the pro-oxidant marker NOX-4. MCH increased expression of genes regulating hypoxia signalling and feedback (HIF-3α, KDM3A, SLC2A1, EGLN-3). There was no effect of MCH on fetal plasma/lung tissue cortisol concentrations, nor genes regulating glucocorticoid signalling (HSD11B-1, HSD11B-2, NR3C1, NR3C2). MCH increased expression of genes regulating sodium (SCNN1-B, ATP1-A1, ATP1-B1) and water (AQP-4) movement in the fetal lung. MCH promoted surfactant maturation (SFTP-B, SFTP-D, ABCA3) at the molecular level, but did not alter the numerical density of surfactant positive cells in lung tissue. MCH in late gestation promotes molecular maturation of the fetal lung, which may be an adaptive response in preparation for the successful transition to air-breathing at birth.

In Vivo Neurochemical Characterization of Developing Guinea Pigs and the Effect of Chronic Fetal Hypoxia

The guinea pig is a frequently used animal model for human pregnancy complications, such as oxygen deprivation or hypoxia, which result in altered brain development. To investigate the impact of in utero chronic hypoxia on brain development, pregnant guinea pigs underwent either normoxic or hypoxic conditions at about 70 % of 65-day term gestation. After delivery, neurochemical profiles consisting of 19 metabolites and macromolecules were obtained from the neonatal cortex, hippocampus, and striatum from birth to 12 weeks postpartum using in vivo (1)H MR spectroscopy at 9.4 T. The effects of chronic fetal hypoxia on the neurochemical profiles were particularly significant at birth. However, the overall developmental trends of neurochemical concentration changes were similar between normoxic and hypoxic animals. Alterations of neurochemicals including N-acetylaspartate (NAA), phosphorylethanolamine, creatine, phosphocreatine, and myo-inositol indicate neuronal loss, delayed myelination, and altered brain energetics due to chronic fetal hypoxia. These observed neurochemical alterations in the developing brain may provide insights into hypoxia-induced brain pathology, neurodevelopmental compromise, and potential neuroprotective measures.

Combined in utero hypoxia-ischemia and lipopolysaccharide administration in rats induces chorioamnionitis and a fetal inflammatory response syndrome

INTRODUCTION

Preterm birth is a major cause of infant morbidity and long-term disability, and is associated with numerous central nervous system (CNS) deficits. Infants exposed to intrauterine inflammation, specifically chorioamnionitis, are at risk for very early preterm birth and neurological complications including cerebral palsy, epilepsy, and behavioral and cognitive deficits. However, placenta-brain axis abnormalities and their relationship to subsequent permanent CNS injury remain poorly defined.

METHODS

Intrauterine injury was induced in rats on embryonic day 18 (E18) by transient systemic hypoxia-ischemia (TSHI) and intra-amniotic lipopolysaccharide (LPS) injection. Placenta, brain and serum were collected from E19 to postnatal day 0 (P0). Histology, TUNEL staining, western blot and multiplex immunoassays were used to quantify placental and brain abnormalities, and fetal serum cytokine levels.

RESULTS

Prenatal TSHI + LPS caused acute and subacute placental injury hallmarked by inflammatory infiltrate, edema, hemorrhage and cell death along with placental increases in IL-1β and TNFα. TSHI + LPS increased a diverse array of circulating inflammatory proteins including IL-1β, TNFα, IL-6, IL-10, IL-4, IFNγ and CXCL1, both immediately after TSHI + LPS and in live born pups. CNS inflammation was characterized by increased CXCL1.

DISCUSSION

Prenatal TSHI + LPS in rats induces placental injury and inflammation histologically consistent with chorioamnionitis, concomitant with elevated serum and CNS pro-inflammatory cytokines. This model accurately recapitulates key pathophysiological processes observed in extremely preterm infants including placental, fetal, and CNS inflammation. Further investigation into the mechanism of CNS injury following chorioamnionitis and the placental-brain axis will guide the use of future interventions.

Fetal endocrine and metabolic adaptations to hypoxia: the role of the hypothalamic-pituitary-adrenal axis

In utero, hypoxia is a significant yet common stress that perturbs homeostasis and can occur due to preeclampsia, preterm labor, maternal smoking, heart or lung disease, obesity, and high altitude. The fetus has the extraordinary capacity to respond to stress during development. This is mediated in part by the hypothalamic-pituitary-adrenal (HPA) axis and more recently explored changes in perirenal adipose tissue (PAT) in response to hypoxia. Obvious ethical considerations limit studies of the human fetus, and fetal studies in the rodent model are limited due to size considerations and major differences in developmental landmarks. The sheep is a common model that has been used extensively to study the effects of both acute and chronic hypoxia on fetal development. In response to high-altitude-induced, moderate long-term hypoxia (LTH), both the HPA axis and PAT adapt to preserve normal fetal growth and development while allowing for responses to acute stress. Although these adaptations appear beneficial during fetal development, they may become deleterious postnatally and into adulthood. The goal of this review is to examine the role of the HPA axis in the convergence of endocrine and metabolic adaptive responses to hypoxia in the fetus.

Role of the sympathetic autonomic nervous system in hypoxic remodeling of the fetal cerebral vasculature

Fetal hypoxia triggers compensatory angiogenesis and remodeling through mechanisms not fully elucidated. In response to hypoxia, hypoxia-inducible factor drives expression of cytokines that exert multiple effects on cerebral structures. Among these, the artery wall is composed of a heterogeneous cell mix and exhibits distinct patterns of cellular differentiation and reactivity. Governing these patterns are the vascular endothelium, smooth muscle (SM), adventitia, sympathetic perivascular nerves (SPN), and the parenchyma. Although an extensive literature details effects of nonneuronal factors on cerebral arteries, the trophic role of perivascular nerves remains unclear. Hypoxia increases sympathetic innervation with subsequent release of norepinephrine (NE), neuropeptide-Y (NPY), and adenosine triphosphate, which exert motor and trophic effects on cerebral arteries and influence dynamic transitions among SM phenotypes. Our data also suggest that the cerebrovasculature reacts very differently to hypoxia in fetuses and adults, and we hypothesize that these differences arise from age-related differences in arterial SM phenotype reactivity and proximity to trophic factors, particularly of neural origin. We provide an integration of recent literature focused on mechanisms by which SPN mediate hypoxic remodeling. Our recent findings suggest that trophic effects of SPN on cerebral arteries accelerate functional maturation through shifts in SM phenotype in an age-dependent manner.

[The effect of hypoxia on cholinesterase activity in rat sensorimotor cortex]

This study reports the dynamics of changes in postnatal ontogenesis of the activity of soluble and membrane-bound forms of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in sensorimotor cortex of rats as well as the pattern of their changes after prenatal hypoxia (E14, 7% O2, 3 h) or acute hypoxia in adult animals (4 months, 7% O2, 3 h). In normally developing rats the activity of the membrane-bound AChE form in the sensorimotor cortex gradually increased up to the end of the first month after birth and remained at this high level during all further postnatal ontogenesis, while the activity of the soluble form of AChE reached its maximum on the 10th day after birth and decreased significantly by the end of the first month. In animals exposed to prenatal hypoxia the activity both of the soluble and membrane bound forms of AChE during the first two weeks after birth was 20-25% lower, as compared to controls but increased by the end of the first month and even exceeded the control values remaining increased up to old age (1.5 years). The activity of both BChE forms in rat sensorimotor cortex at all stages of postnatal ontogenesis was significantly lower than of AChE, although the dynamics of their changes was similar to that of AChE. Prenatal hypoxia led to a decrease in the activity of the membrane-bound form of BChE, as compared to controls, practically at all developmental stages studied, but was higher at the end of the first month after birth. At the same time, the activity of the soluble form of BChE was decreased only on the 20th day of development, as compared to the control, but increased from the end of the first month of life onwards. Acute hypoxia in adult rats also led to a decrease in the activity of both forms of AChE and BChE in the sensorimotor cortex but the dynamics of these changes was different for each enzyme. Thus, insufficient oxygen supply to the nervous tissue at different stages of ontogenesis has a significant effect on the activity and ratio of various forms of cholinesterases exhibiting either growth factor or signaling properties. This may lead to changes in brain development and formation of behavioural reactions, including learning and memory, and also increase the risk of development of the sporadic form of Alzheimer's disease (AD)--one of the most common neurodegenerative diseases of advanced age. This study expands our knowledge of the properties of brain cholinesterases under normal and pathological conditions and may be useful for developing new approaches towards prevention and treatment of AD.

[Prenatal hypoxia modifies working memory and the activity of hippocampal polyphosphoinositide system in rats]

The present study was aimed at the analysis of spatial learning abilities in the Morris water maze (working memory) as well as hippocampal levels of phosphatidylinositol 4,5-diphosphates (TPI), phosphatidylinositol 4-phosphates (DPI), phosphotidylinositols (MPI), and expression of the type 1 inositol 1,4,5-trisphosphate receptor (IR3R1) in rats exposed to severe hypobaric hypoxia (ascent to 11 km, 3 h) on prenatal days 14-16 (group 1) or 17-19 (group 2). Exposure to severe hypoxia led to significant elevation of TP 1 and DPI hippocampal levels in juvenile and adult rats in the group 1, however these changes were more pronounced in juvenile rats than in adults. In the group 2, hypoxia up-regulated TPI and DPI hippocampal levels in juvenile rats, but in adult animals of this group just a small TPI level up-regulation was detected. Activation of IR3R1 expression was found to occur in the hippocampus both of juvenile and adult rats in the groups 1 and 2. These finding are consistent with the impaired spatial learning ability we revealed in the Morris water maze, indicative of a working memory deficit in the rat offspring exposed to hypobaric hypoxia during the first half of the last week of pregnancy.

[Influence of chronic hypoxia on optical density of μ-opioid receptors in fetal rat brain]

Fetal brain is considered to be the major body organ, critical for the future quality of human life. Offspring exposed to prenatal hypoxia has been evidenced to experience behavioral abnormalities as a result of the injury sustained by neuronal cells in the brain. The relatively early appearance of opioid receptors proved susceptible to endogenous and exogenous factors. Increased concentrations of neurotransmitters in the maternal circulation and amniotic fluid induced by hypoxic exposure imply their role in the regulation of cellular division and differentiation processes. Endogenous neuropeptides and specific opioid receptors are distributed in those brain structures that are associated with behavior and reproduction. Fetuses exposed to the adverse effects of increased opioid level incur structural brain tissue abnormalities.

OBJECTIVES

The present study seeks to determine the effects of long-term hypoxic exposure during gestation on the expression of opioid receptors in specific brain regions in both sexes.

MATERIAL AND METHODS

The study was conducted on pregnant Sprague-Dawley rats, (120 days old, body weight between 250 and 300 g). Experiments were carried out in order to determine the effect of long-term hypoxia on μ-opioid receptor density in selected structures of fetal central nervous system: caudate-putamen (CPu), zona germinata (ZG), nucleus accumbens (NA), olfactory tubercle (OT), Median Part Medial Preoptic Area (MMPoA) and Lateral Part Medial Preoptic Area (LMPoA). Pregnant female rats were assigned to two research groups: the control group (N=6) and the experimental group subject to prolonged hypoxia for 24 hours from the gestational day 15 to gestational day 20 (E-15-E20). At E-21 rats were sacrificed, their fetuses were removed and their brains were incubated with radioligands. The μ-opioid receptor incubation in selected brain structures was performed with a specific radioisotope [3H]DAMGO [tyrosyl-3,5,-3H(N)-D-Ala-Gly-N-methyl-Phe-Gly-enkephalin]. Optical density of μ-opioid receptors was determined at E-21 of gestation during long-term exposure to chronic hypoxia induced from E-15 to E-21 of gestation. Experimental model coupled with an innovative autoradiography allowed for a precise assessment of the lesions sustained by fetal brain tissues due to hypoxia and the adaptive mechanisms of the central nervous system in reaction to hypoxic exposure.

RESULTS

Statistically significant chronic hypoxia (p<0.05) downregulated the values of μ-opioid receptors optical density in relation to control group in CPu and ZG. Chronic hypoxia in ZG substantially reduces the values of μ-opioid receptors optical density in males (p<0.05). The differences among remaining groups did not show to be statistically significant.

CONCLUSIONS

The obtained results of μ-opioid receptor expression can be detected in specific fetal brain regions that mediate sexual behavior and may be attributable to behavioral changes of experimental animals due to hypoxic exposure during gestation.

[Nitric oxide production at pregnant rats and feature postnatal systemogenesis at their posterity developing at insufficiency of disturbance of utero-placental blood circulation]

Disturbance of uteroplacental circulation at white rats considerably reduces percent of survival rate of posterity. Hyperfunction of erythrocyte system and NO-dependent mechanisms of regulation in the first days of pups' life results in an exhaustion of their functional reserves.

[Protection effect of recombiant human erythropoietin preconditioning against intrauterine hypoxic-ischemic brain injury and its influence on expression of caspase-3 protein in brain tissue]

OBJECTIVE

To investigate the effects of recombine human erythropoietin (rhEPO) on neural cells apoptosis and the expression of Caspase-3 protein in brain tissue of fetal rats after intrauterine hypoxic-ischemic brain injury.

METHODS

Forty-four Sprague-Dawley rats on 19 days of pregnancy were divided into rhEPO treated group, ischemia-reperfusion group and sham-operated group. Intrauterine hypoxic-ischemic injury of fetal rats was induced by bilateral occlusion of the utero-ovarian artery for 20 min. rhEPO (5000 U/kg) was injected into rats through caudal vein in rhEPO treated group while saline was injected into rats in hypoxic-ischemic group 30 min before hypoxic-ischemic injury. The brain samples in rhEPO treated group and hypoxic-ischemic group were obtained at 30 min, 3 h, 6 h, 24 h and 48 h respectively after artery clamping. There was no hypoxic-ischemic injury in sham-operated group, so the brain samples were obtained at 24 hours after sham operation. Neuroapoptosis in brain tissue was measured by TdT mediated dUTP-biotin nick end labeling (Tunel) staining. The expression of Caspase-3 protein was observed by immunohistochemistry.

RESULTS

The number of apoptosis cells in fetal rat hippocampus after intrauterine hypoxic-ischemic increased progressively with reperfusion. Compared with the I/R group, the number of apoptosis cells decreased in rhEPO treated group (P < 0.01). The expression of Caspase-3 increased rapidly after 3 hours from the reperfusion in the I/R group. Compared with the I/R group, there was less expression of Caspase-3 in rhEPO treated group (P < 0.01).

CONCLUSION

rhEPO showed the effects to inhibit the apoptosis of fetal neural cells and the expression of Caspase-3 protein due to intrauterine hypoxic-ischemic brain injury.

Ontogeny and the effects of in utero brain ischemia on interleukin-1β and interleukin-6 protein expression in ovine cerebral cortex and white matter

Interleukin (IL)-1β and IL-6 have been implicated in brain development, injury progression, and fetal/maternal immune interactions. We examined IL-1β and IL-6 protein expression in cerebral cortex (CC) and white matter (WM) from non-ischemic ovine fetuses at 87-90, 122-127, and 135-137 days of gestation, pregnant ewes at 87-90 and 135-137 days of gestation, and fetuses exposed to 48 or 72h of reperfusion after ischemia. Protein expression was determined by Western immunoblot. In non-ischemic CC, IL-1β was higher (P<0.05) in adult sheep and fetuses at 135-137 than 87-90 and 122-127 days, and IL-6 higher at 122-127 than 87-90 days, and in adults than fetuses at 87-90, 122-127, and 135-137 days of gestation. In non-ischemic fetal WM, IL-6 was higher at 135-137 than 87-90 days, but IL-1β did not differ. In CC, IL-1β was higher in ewes at 135-137 than 87-90 days and IL-6 at 135-137 days and in non-pregnant adults than ewes at 87-90 days of gestation. In WM, IL-1β was higher in ewes at 135-137 than 87-90 days of gestation, but IL-6 did not differ. Forty-eight and 72h after ischemia, CC IL-1β was higher than in non-ischemic fetuses. Seventy-two hours after ischemia, IL-1β and IL-6 were higher in WM than CC. In conclusion, IL-1β and IL-6 exhibit developmental regulation in fetal brain, change during gestation in brains of pregnant ewes, show regional differences in normal brains of fetuses and ewes, demonstrate differential responses after ischemia in CC and WM, and IL-1β but not IL-6 increases after ischemia in CC.

Differential effect of intrauterine hypoxia on caspase 3 and DNA fragmentation in fetal guinea pig hearts and brains

The aim of this study is to quantify the effect of intrauterine hypoxia (HPX) and the role of nitric oxide (NO) on the apoptotic enzyme, caspase 3, and DNA fragmentation in fetal heart and brain. Hypoxia and NO are important regulators of apoptosis, although this has been little studied in the fetal organs. We investigated the effect of intrauterine HPX on apoptosis and the role of NO in both fetal hearts and brains. Pregnant guinea pigs were exposed to room temperature (N = 14) or 10.5% O₂ (N = 12) for 14 days prior to term (term = 65 days) and administered water or L-N6-(1-iminoethyl)-lysine (LNIL), an inducible nitric oxide synthase (iNOS) inhibitor, for 10 days. Fetal hearts and brains were excised from anesthetized near-term fetuses for study. Chronic HPX decreased pro- and active caspase 3, caspase 3 activity, and DNA fragmentation levels in fetal hearts compared with normoxic controls. L-N6-(1-iminoethyl)-lysine prevented the HPX-induced decrease in caspase 3 activity but did not alter DNA fragmentation levels. In contrast, chronic HPX increased both apoptotic indices in fetal brains, which were inhibited by LNIL. Thus, the effect of HPX on apoptosis differs between fetal organs, and NO may play an important role in modulating these effects.

Left-right difference in fetal liver oxygenation during hypoxia estimated by BOLD MRI in a fetal sheep model

OBJECTIVE

The purpose of this study was to measure differences in oxygenation between the left and right sides of the fetal liver during varying oxygenation levels.

METHODS

Eight ewes carrying singleton fetuses at gestational age 125 days (term, 145 days) were included in the study. Under anesthesia the ewes were ventilated with gas containing different levels of oxygen, thereby subjecting the fetuses to hyperoxia (mean ± SD maternal arterial partial pressure of oxygen (pO2), 23.2 ± 8.2 kPa) and hypoxia (mean maternal arterial pO2, 7.1 ± 0.5 kPa). Changes in oxygenation within the fetal liver were assessed by blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI).

RESULTS

During hyperoxia there was no difference between the BOLD signal in the left and right sides of the fetal liver; mean change in BOLD (ΔBOLD)(hyperox), -0.9 ± 3.7%. During hypoxia, however, the decrease in the BOLD signal was more pronounced in the right side as compared with the left side, thereby creating a significant increase in the left-right difference in the BOLD signal; mean ΔBOLD(hypox), 5.2 ± 2.2% (P = 0.002, paired t-test). The left-right difference was directly proportional to the degree of hypoxia (R2 = 0.86, P = 0.007).

CONCLUSIONS

To our knowledge, this is the first study demonstrating differences in oxygenation between the left and right sides of the fetal liver during hypoxia, a difference that can be explained by increased ductus venosus shunting. Thus, the BOLD MRI technique is a promising non-invasive tool that might be useful for the future monitoring of the human fetus.

[Biochemical aspects of fetal hypoxia]

OBJECTIVE

To evaluate validity of biochemical diagnostic methods of fetal hypoxia.

DESIGN

A case-control study.

SETTING

Department of Gynecology and Obstetrics, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic.

METHODS

We included 67 patients, and they were retrospectively divided into group of controls (n=36), and studied group (n=31) according to pH in umbilical artery (UA) <7.15. Acid-base parameters were assessed with Rapidlab 248, Bayer Healthcare LLC, East Walpole, USA. We determined criterion for metabolic acidosis (MAC) as pH UA <7.15, resp. base deficit (BD) UA >12 mmol/l. Postpartal lactate concentration in umbilical vein (UV) and UA was determined with lactatemeter Accutrend Lactate, Roche Diagnostics, Switzerland. Quantitative assessment of fetal human protein S100B was provided with ELISA (Sangtec 100 ELISA, DiaSorin Inc., Stillwater, Minnesota, USA). Fetal erythropoietin concentration in UV was examined with immunoenzymatic assessment Access EPO (Beckman Coulter, Inc., Fullerton, CA, USA).

STATISTICS

histograms, Kolmogorov-Smirnov test, Mann-Whitney test, Spearman's rho; statistical significance: p<0.05, Receiver Operating Characteristic curves, Area Under the Curve.

RESULTS

The best correlation was between fetal acid-base parameters and lactate in UA (p<0.0005). Significant correlation was between EPO in UV, and protein S100B in UV (p<0.05). EPO in UV significantly correlated with lactate in UA (p<0.05). Correlation between EPO in UV and protein S100B was not significant. According to ROC curves in prediction of fetal hypoxia, we found an excellent accuracy (AUC>0.9) for lactate in UA, good accuracy (AUC>0.7) had EPO in UV. Results for protein S100B were not significant. The highest sensitivity had EPO in UV, while the highest specificity has had lactate in UA.

CONCLUSION

An indisputable evidence of labor management quality is the fetal metabolic status. On the basis of our results, the suitable clinical markers are lactate and EPO, in addition to acid-base parameters.

Application of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry method to identify potential biomarkers of perinatal asphyxia in a non-human primate model

Perinatal asphyxia is a leading cause of brain injury in infants, occurring in 2-4 per 1000 live births. The clinical response to asphyxia is variable and difficult to predict with current diagnostic tests. Reliable biomarkers are needed to help predict the timing and severity of asphyxia, as well as response to treatment. Two-dimensional gas chromatography-time-of-flight-mass spectrometry (GC×GC-TOFMS) was used herein, in conjunction with chemometric data analysis approaches for metabolomic analysis in order to identify significant metabolites affected by birth asphyxia. Blood was drawn before and after 15 or 18 min of cord occlusion in a Macaca nemestrina model of perinatal asphyxia. Postnatal samples were drawn at 5 min of age (n=20 subjects). Metabolomic profiles of asphyxiated animals were compared to four controls delivered at comparable gestational age. Fifty metabolites with the greatest change pre- to post-asphyxia were identified and quantified. The metabolic profile of post-asphyxia samples showed marked variability compared to the pre-asphyxia samples. Fifteen of the 50 metabolites showed significant elevation in response to asphyxia, ten of which remained significant upon comparison to the control animals. This metabolomic analysis confirmed lactate and creatinine as markers of asphyxia and discovered new metabolites including succinic acid and malate (intermediates in the Krebs cycle) and arachidonic acid (a brain fatty acid and inflammatory marker) as potential biomarkers. GC×GC-TOFMS coupled with chemometric data analysis are useful tools to identify acute biomarkers of brain injury. Further study is needed to correlate these metabolites with severity of disease, and response to treatment.

Nitric oxide inhibits ACTH-induced cortisol production in near-term, long-term hypoxic ovine fetal adrenocortical cells

We previously reported that in the sheep fetus, long-term hypoxia (LTH) resulted in elevated basal plasma adrenocorticotropic hormone (ACTH(1- 39)) whereas the cortisol levels were not different from normoxic controls. We also showed that LTH enhances endothelial nitric oxide synthase (eNOS) expression in the fetal adrenal. This study was designed to determine the effect of NO on cortisol production in adrenocortical cells from LTH fetal sheep. Ewes were maintained at high altitude (3820 m) from ∼40 days' gestation (dG) to near term. Between 138 and 141 dG, fetal adrenal glands were collected from LTH and age-matched normoxic control fetuses. Adrenal cortical cells were pretreated with sodium nitroprusside (SNP), nitro-L-arginine methyl ester (L-NAME), L-arginine, or diethyleneamine NO (DETA-NO) and then challenged with 10 nmol/L ACTH. Cortisol responses were compared after 1 hour. Adrenocorticotropic hormone -induced cortisol secretion was significantly higher in LTH versus control (P < .01). Enhancement of NO with L-arginine resulted in a significant reduction of ACTH-mediated cortisol production in the LTH group. DETA-NO also caused a significant decrease in ACTH-mediated cortisol production (P < .05). Inhibition of NOS with L-NAME significantly increased cortisol production in the LTH group (P < .05 compared to ACTH alone), whereas the effect on the control group was not significant. Nitric oxide synthase activity was significantly higher in the LTH group compared to control, but this difference was eliminated following ACTH treatment. These data indicate that LTH enhances adrenal cortical sensitivity to the inhibitory effects of NO on cortisol production. Nitric oxide may, therefore, play an important role in regulating ACTH-induced cortisol production in the LTH fetal adrenal.

Non-invasive detection and quantification of human foetal brain lactate in utero by magnetic resonance spectroscopy

OBJECTIVE

To assess the feasibility of foetal cerebral lactate detection and quantification by proton magnetic resonance spectroscopy ((1)H-MRS) in pregnancies at increased risk of cerebral hypoxia, using a clinical 1.5 T magnetic resonance imaging (MRI) system.

METHOD

Localised (1)H-MRS was performed in four patients with pregnancies in their third trimester complicated by intrauterine growth restriction (IUGR). A long echo time (TE) of 288 ms was used to maximise detection and conspicuity of the lactate methyl resonance, together with a short TE MRS acquisition to check for the presence of lipid contamination. Individual peaks in the resulting spectra were measured, corrected for relaxation and referenced to the unsuppressed water signal to provide metabolite concentrations.

RESULTS

A resonance peak consistent with the presence of lactate was observed in all cases. In one subject, this was confounded by the identification of significant lipid contamination in the short TE MRS acquisition. The range of measured lactate concentrations was 2.0-3.3 mmol/kg and compared well with preterm neonatal MRS studies.

CONCLUSION

The non-invasive detection and quantification of foetal cerebral lactate by MRS is achievable on a clinical 1.5 T MRI system.

The effects of hypoxia on growth cones in the ovine fetal brain

OBJECTIVE

This study was designed to investigate the effects of hypoxia on neural process proliferation by studying its effects on growth cone tubulin and insulin-like growth factor (IGF)-I receptor content.

METHODS

Six fetal lambs were catheterized in the brachial artery and vein. Maternal oxygenation was reduced in steps from a fractional inspired oxygen concentration (FiO2) of 20% to 6% by addition of nitrogen to the inhaled gas mixture for a period of 4 h of reduced oxygen intake. Fetal arterial blood was sampled after the maternal FiO2 and oxygen were stable for >5 min at maternal FiO2 of 20% to 6%. Controls were obtained from normoxic fetuses whose ewes had similar surgery and were kept at an FiO2 of 20% throughout the experiment. Growth cones were isolated from the fetal cerebrum and cerebellum. alpha-tubulin and IGF-I receptors were quantified by immunoblotting. Tubulin and IGF-I receptor mRNA expressions were quantified by real-time polymerase chain reaction.

RESULTS

Maternal nitrogen breathing reduced fetal arterial pH from 7.32+/-0.06 to 6.99+/-0.02 (p<0.001). Hypoxia increased IGF-I receptors from 143+/-10 to 327+/-14 (p<0.001) and from 272+/-26 to 396+/-34 (p<0.001) fluorescence units/microg protein in the cerebrum and cerebellum, respectively. It also increased alpha-tubulin from 713+/-30 to 1873+/-126 (p<0.001) and from 780+/-34 to 2362+/-79 (p<0.001) fluorescence units/microg protein in the cerebrum and cerebellum, respectively. Expression of IGF-I receptor mRNA increased significantly in the hypoxic animals both in the cerebrum and the cerebellum, but there was no change in expression of alpha-tubulin mRNA.

CONCLUSIONS

This increase in IGF-I receptor expression and growth cone content may be an adaptive response to hypoxia to maintain neurite growth by facilitating binding of IGF-I. Hypoxia also increased the growth cone level of alpha-tubulin but did not increase its mRNA expression, which may indicate an inability to polymerize tubulin and build microtubules.

[Permeability of exogenetic recombine human erythropoietin through placenta barrier to fetal rats with transient uteroplacental ischemia]

OBJECTIVE

To investigate whether recombine human erythropoietin can cross the placenta barrier in rats with transient uteroplacental ischemia.

METHODS

Rats on day 19 of pregnancy were divided into ischemia-reperfusion group, sham-operated group and rhEPO treated group. Fetal ischemia was induced by bilateral occlusion of the utero-ovarian artery for 20 minutes. 125I-rhEPO or saline were administered intravenously 30 min before the induction of hypoxic-ischemic injury. Fetal rat organs were removed to measure the radioactivity post injury.

RESULTS

A small amount of radioactive activity (1.26 +/- 0.28) pg/g was detected in the fetal rats with ischemia-reperfusion. 125I-rhEPO radioactivity increased gradually with time in the placenta, amniotic fluid and fetal tissues of vital organs in the rats of sham-operated group and rhEPO treatment group. There were significant differences in 125I-rhEPO between placental organs and other organs (P < 0.05). The permeability of 125I-rhEPO through the blood brain barrier changed with reperfusion time and peaked about 6 h after reperfusion, and significant differences were found between rhEPO treatment group and sham operation group (P < 0.05).

CONCLUSION

Exogenous rhEPO can cross the placenta barrier and blood-brain barrier and reach hypoxic-ischemic fetal rats.

[Dopamine D4 receptor hypoxia sensitivity and child psychiatric disorders]

Attention-deficit hyperactivity disorder (ADHD) is one of the most frequent child psychiatric problems with a complex genetic and environmental background. According to the prevailing view, main factors of the disorder are prefrontal dopamine deficiency and incomplete central dopaminergic functioning. Twin studies suggest substantial heritability in the background of the disease, and the studied candidate genes involve components of the dopamine system. Moreover, various noxious pre- and perinatal environmental impacts have been implicated in the pathogenesis of ADHD. Here we review experimental results from epidemiological, tissue and animal studies that assigned a causal role to fetal hypoxia in the development of ADHD and pointed out that the dopaminergic neurotransmission is sensitive to hypoxia. Allelic variants of the D4 dopamine receptor (DRD4) are well characterized risk factors of ADHD. Recently we have reported that hypoxia enhanced the promoter activity of DRD4 gene several fold. These observations suggest that the effect of hypoxia on the dopaminergic neurotransmission might be an important factor in the pathomechanism of ADHD.

The relation of S100beta and metabolic and endocrine responses to acute fetal hypoxemia

Elevations in S100beta protein in umbilical cord blood have been proposed as a reproducible marker of fetal stress, leading to cell damage within the central nervous system. However, it remains unknown whether fetal S100beta concentrations correlate with established endocrine and metabolic indices of fetal distress. Hence, in the late gestation ovine fetus, plasma concentrations of S100beta, adrenocorticotropic hormone (ACTH), cortisol, neuropeptide Y (NPY), and catecholamines and blood concentrations of glucose and lactate were measured during acute hypoxemia. Under general anesthesia, 5 sheep fetuses were chronically instrumented with catheters and subjected 5 days later to 1h normoxia, 0.5h hypoxemia and 1h recovery. Plasma samples were taken during each experimental period. Hypoxemia induced significant falls in PaO2 with increases in fetal plasma concentrations of ACTH, cortisol, catecholamines and NPY, and elevations in blood glucose and lactate, all of which showed significant positive relationships with fetal plasma S100beta concentrations. Hence, evaluation of S100beta may provide a valuable clinical tool in the assessment of fetal well-being in suspected complicated pregnancies.

[Effect of intrauterine hypoxia upon newborn albino rat tooth germ cells anabolic activity]

The aim of this study was to examine the intrauterine hypoxia influence on dental hard tissue development. Pregnant rats were exposed in hypoxic environments between day 14 and 19 of pregnancy. The study was performed on 36 newborn albino rats. Analysis of nucleolar organizator parameters were performed in enameloblasts, odontoblasts and saliva gland epitheliocytes. Data obtained demonstrated that intrauterine hypoxia decreased nucleolar organizator quantity in enameloblasts of tooth germ.

Maturation and long-term hypoxia alters Ca2+-induced Ca2+ release in sheep cerebrovascular sympathetic neurons

The contribution of sympathetic nerves arising from the superior cervical ganglia (SCG) toward the growth and function of cerebral blood vessels is pertinent throughout maturation as well as in response to cardiovascular stress imposed by high-altitude long-term hypoxia (LTH). The function of SCG sympathetic neurons is dependent on intracellular Ca2+ concentration ([Ca2+]i) signaling, which is strongly influenced by a process known as Ca(2+)-induced Ca2+ release (CICR) from the smooth endoplasmic reticulum (SER). In this study, we used the sheep SCG neuronal model to test the hypotheses that maturation decreases CICR and high-altitude LTH depresses CICR in fetal SCG neurons but not in those of the adult. We found that the contribution of CICR to electric field stimulation (EFS)-evoked [Ca2+]i transients was greatest in SCG cells from normoxic fetuses and was abolished by LTH. The decline in CICR was associated with a reduction in sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) function in fetal SCG cells during LTH, reducing SER Ca2+ levels below the threshold needed for the coupling of Ca2+ influx and CICR. With respect to the maturation from the fetus to adult, the decrease in CICR may reflect both a reduction in the levels of ryanodine receptor isoforms 2 and 3 and SERCA function. In response to LTH and in contrast to the fetus, CICR function in adult SCG cells is maintained and may reflect alterations in other mechanisms that modulate the CICR process. As CICR is instrumental in the function of sympathetic neurons within the cerebrovasculature, the loss of this signaling mechanism in the fetus may have consequences for the adaptation to LTH in terms of fetal susceptibility to vascular insults.

Tetrahydrobiopterin in the prevention of hypertonia in hypoxic fetal brain

OBJECTIVE

Tetrahydrobiopterin (BH(4)) deficiency is a cause of dystonia at birth. We hypothesized that BH(4) is a developmental factor determining vulnerability of the immature fetal brain to hypoxic-ischemic injury and subsequent motor deficits in newborns.

METHODS

Pregnant rabbits were subjected to 40-minute uterine ischemia, and fetal brains were investigated for global and focal changes in BH(4). Newborn kits were assessed by neurobehavioral tests following vehicle and sepiapterin (BH(4) analog) treatment of dams.

RESULTS

Naive fetal brains at 70% gestation (E22) were severely deficient for BH(4) compared with maternal and other fetal tissues. BH(4) concentration rapidly increased normally in the perinatal period, with the highest concentrations found in the thalamus compared with basal ganglia, frontal, occipital, hippocampus, and parietal cortex. Global sustained 40-minute hypoxia-ischemia depleted BH(4) in E22 thalamus and to a lesser extent in basal ganglia, but not in the frontal, occipital, and parietal regions. Maternal supplementation prior to hypoxia-ischemia with sepiapterin increased BH(4) in all brain regions and especially in the thalamus, but did not increase the intermediary metabolite, 7,8-BH(2). Sepiapterin treatment also reduced incidence of severe motor deficits and perinatal death following E22 hypoxia-ischemia.

INTERPRETATION

We conclude that early developmental BH(4) deficiency plays a critical role in hypoxic-ischemic brain injury. Increasing brain BH(4) via maternal supplementation may be an effective strategy in preventing motor deficits from antenatal hypoxia-ischemia.

MCI-186 administered to the maternal circulation inhibits fetal brain injury resulting from total umbilical cord occlusion in the chronically instrumented fetal lamb

OBJECTIVE

To evaluate the transplacental effects of MCI-186 (edaravone), a potent hydroxyl radical scavenger, administered to the maternal circulation to inhibit fetal brain injury caused by umbilical cord occlusion.

METHODS

Nine chronically instrumented lambs were prepared. In three cases, 10-min persistent total umbilical cord occlusion (group A) was performed. Another three cases underwent occlusion and were administered 60 mg of MCI-186 through the maternal femoral vein prior to the end of occlusion (group B). The remaining three cases underwent sham operation (group C). On day 3 after insult, fetal brains were extirpated. Paraffin-embedded brain tissue sections were stained with hematoxylin and eosin, Bodian, Kluver-Barrera, and TUNEL. Neuronal cellular damage was evaluated by two pathologists blinded to the experimental conditions.

RESULTS

Group A displayed numerous cells with eosinophilic condensation of nuclear chromatin and proliferation of microglia in the hippocampus and basal ganglia. TUNEL-positive cells were observed in the periventricular area. Group B showed microglial proliferations, but no marked changes. No pathological changes were apparent in group C.

CONCLUSIONS

MCI-186 administered to the maternal circulation could inhibit fetal brain injury resulting from hypoxia-reperfusion induced by umbilical cord occlusion.

Changes in beta(1) integrin in renal tubular epithelial cells after intrauterine asphyxia of rabbit pups

OBJECTIVE

We investigated the role of beta(1) integrin in acute renal tubular injury caused by intrauterine asphyxia of neonatal rabbits by exploring the distribution and expression changes in beta(1) integrin and its mRNA in renal tubular epithelial cells.

METHODS

A catheter was used to temporarily block the abdominal aortas of New Zealand pregnant rabbits in order to set up the intrauterine asphyxia animal model. The rabbit pups were randomly divided into control, asphyxia, and calpain inhibitor intervention groups and their renal tubular tissues were examined at 2 h after asphyxia. Immunofluorescence and in situ hybridization were used to examine the expression of beta(1) integrin and its mRNA, respectively. Western blot analysis was used to show the proteolysis of beta(1) integrin. Calpain inhibitor I was used to show the protective effect of keeping beta(1) integrin from being hydrolyzed after asphyxia.

RESULTS

(1) Normally, beta(1) integrin was located exclusively at the basal surface of renal tubular epithelial cells. After asphyxia a large amount of beta(1) integrin shifted from the basal surface to the cytoplasma and the lateral and apical surfaces and its expression decreased significantly, with simultaneous damage to renal tubular integrity and structure, many exfoliated cells and cell fragments obstructed the tubular lumen. (2) The mRNA of beta(1) integrin was mainly expressed in the cytoplasma. After asphyxia its expression increased significantly. (3) Proteolysis of beta(1) integrin was evident after asphyxia, but was significantly reduced in the calpain inhibitor intervention group. Calpain inhibitor I prevented the decrease and dislocation of beta(1) integrin and protected renal tubular integrity and structure.

CONCLUSION

Intrauterine asphyxia caused proteolysis of beta(1) integrin, with reduced expression and depolarized distribution, leading to tubular lumen obstruction and renal tubule destruction. Damage to beta(1) integrin and the renal tubule was related to the activation of calpain, and calpain inhibitor curtailed these effects.

Amniotic fluid S100B protein and erythropoietin in pregnancies at risk for fetal hypoxia

OBJECTIVE

S100B protein is a biochemical marker for brain injury, and high serum S100B levels have been observed in newborns with birth asphyxia. We hypothesized that the concentration of amniotic fluid erythropoietin, which increases in chronic fetal hypoxia, correlates with amniotic fluid S100B concentration.

STUDY DESIGN

Amniotic fluid samples in 35 pregnancies at high risk for chronic fetal hypoxia were obtained at cesarean section or by amniocentesis done within a median of 2 days before delivery. S100B and erythropoietin concentrations were measured by chemiluminescent immunoassays.

RESULTS

A positive correlation existed between the concentrations of S100B and erythropoietin in the amniotic fluid (r=0.57, p<0.0001). Amniotic fluid S100B concentration was higher (70 ng/l; 33-469, n=17) (median; range) in pregnancies with elevated amniotic fluid erythropoietin (>or= 50 IU/l) than in pregnancies with normal erythropoietin (34 ng/l; 20-340, n=18) (p<0.0001, Mann-Whitney U-test). S100B predicted an elevated amniotic fluid erythropoietin concentration in the study population with the sensitivity of 94% and specificity of 83%.

CONCLUSION

A strong positive correlation exists between amniotic fluid S100B and erythropoietin concentrations in pregnancies at high risk for chronic fetal hypoxia. This suggests that chronic fetal hypoxia increases the intrauterine release of S100B.

Nitric oxide synthesis in placenta is increased in intrauterine growth restriction and fetal hypoxia

In order to study the possible role of nitric oxide (NO) in the human placenta, we measured the concentration of its stable metabolite nitrite (NO2-) in the placentas of women with normal pregnancies and those from pregnancies complicated by intrauterine growth restriction (IUGR) with or without fetal hypoxia. We have measured nitrites by the Griess reaction in 15 placentas from IUGR pregnancies and 12 controls. Cerebroumbilical ratio (C:U) was recorded by color Doppler ultrasound and values below 1 were considered to be a predictor for fetal hypoxia. NO2- levels measured in pathological placentas were increased for at least 93% as compared to control. Subjects from pregnancies complicated by IUGR and fetal hypoxia had increased NO2- as compared to the placentas from pregnancies with IUGR and normal fetal oxygenation. NO production in placenta is increased in pregnancies with IUGR. This effect is more pronounced in those with compromised fetal oxygenation.

Maternal creatine: does it reach the fetus and improve survival after an acute hypoxic episode in the spiny mouse (Acomys cahirinus)?

OBJECTIVE

We hypothesized that elevating creatine in the maternal diet would reach fetal and placental tissues and improve fetal survival after acute hypoxia at birth.

STUDY DESIGN

Pregnant spiny mice were fed a control or 5% creatine-supplemented diet from day 20 of gestation (term, approximately 39 days). On days 37-38, intrauterine hypoxia was induced by placement of the isolated uterus in a saline solution bath for 7.5-8 minutes, after which fetuses were expelled from the uterus and resuscitation was attempted by manual palpation of the chest. Total creatine content (creatine + phosphocreatine) of placental, fetal, and maternal organs was measured.

RESULTS

The maternal creatine diet significantly increased total creatine content in the placenta, fetal brain, heart, liver, and kidney and increased the capacity of offspring to survive birth hypoxia. Maternal creatine improved postnatal growth after birth hypoxia.

CONCLUSION

This study provides evidence that creatine has potential as a prophylactic therapy for pregnancies that are classified as high risk for fetal hypoxia.

Neurosteroids in the fetus and neonate: Potential protective role in compromised pregnancies

Complications during pregnancy and birth asphyxia lead to brain injury, with devastating consequences for the neonate. In this paper we present evidence that the steroid environment during pregnancy and at birth aids in protecting the fetus and neonate from asphyxia-induced injury. Earlier studies show that the placental progesterone production has a role in the synthesis and release of neuroactive steroids or their precursors into the fetal circulation. Placental precursor support leads to remarkably high concentrations of allopregnanolone in the fetal brain and to a dramatic decline with the loss of the placenta at birth. These elevated concentrations influence the distinct behavioral states displayed by the late gestation fetus and exert a suppressive effect that maintains sleep-like behavioral states that are present for much of fetal life. This suppression reduces CNS excitability and suppresses excitotoxicity. With the availability of adequate precursors, mechanisms within the fetal brain ultimately control neurosteroid levels. These mechanisms respond to episodes of acute hypoxia by increasing expression of 5alpha-reductase and P450scc enzymes and allopregnanolone synthesis in the brain. This allopregnanolone response, and potentially that of other neurosteroids including 5alpha-tetrahydrodeoxycorticosterone (TH-DOC), reduces hippocampal cell death following acute asphyxia and suggests that stimulation of neurosteroid production may protect the fetal brain. Importantly, inhibition of neurosteroid synthesis in the fetal brain increases the basal cell death suggesting a role in controlling developmental processes late in gestation. Synthesis of neurosteroid precursors in the fetal adrenal such as deoxycorticosterone (DOC), and their conversion to active neurosteroids in the fetal brain may also have a role in neuroprotection. This suggests that the adrenal glands provide precursor DOC for neurosteroid synthesis after birth and this may lead to a switch from allopregnanolone alone to neuroprotection mediated by allopregnanolone and TH-DOC.

Chronic hypoxia differentially increases glutathione content and gamma-glutamyl cysteine synthetase expression in fetal guinea pig organs

OBJECTIVE

Glutathione is a natural antioxidant in the fetus and adult. We sought to determine whether maternal hypoxia alters glutathione levels in fetal organs as an adaptive response to the reduced oxygenation.

STUDY DESIGN

Timed pregnant guinea pigs were housed in either a Plexiglas chamber containing 10.5% O(2) from 46 to 60 days gestation (HPX, n=6) or in room air, as the normoxic control (NMX, n=5). Pregnant guinea pigs were anesthetized at near term ( approximately 60 days, term=65 days) and liver, lungand kidney were excised from anesthetized fetuses and stored frozen (-80 degrees C) prior to sample processing. Using the hypoxia marker, pimonidazole, we measured a hypoxia-induced increase in stained cells of fetal liver compared to no change in either the lung or kidney. To measure the effect of hypoxia among different organs, total glutathione (GSH) content and protein levels of gamma-glutamyl cysteine synthetase (gamma-GCS) were measured from the same organs.

RESULTS

Maternal hypoxia increased (P<0.05) total glutathione levels by 121% in the fetal liver but had no effect in either fetal lung or kidney. Chronic hypoxia increased (P<0.05) gamma-GCS protein levels in all three fetal organs studied.

CONCLUSION

These results demonstrate that the fetal response to maternal hypoxia may be organ specific. The increase in fetal liver glutathione via upregulation of gamma-GCS may be an important adaptive response to prolonged hypoxic stress.

Oxygen restriction of neonate rats elevates neuregulin-1α isoform levels: Possible relationship to schizophrenia

Neuregulin-1 (NRG-1), a replicated gene in schizophrenia-association studies, exhibits six mRNA-types and two types of the EGF-like domain, alpha and beta. The beta-isoform was extensively studied, less is known about the extent and specific localization of adult brain NRG-1alpha. NRG-1alpha protein levels were reported reduced in postmortem prefrontal-cortex of schizophrenia patients. NRG-1 type I mRNA levels were found higher in postmortem brain in schizophrenia. In an attempt to decipher between a genetic or environmental involvement in the differences in NRG-1 levels in postmortem brain in schizophrenia, and since obstetric complications were suggested non-genetic risk-factors of schizophrenia, we studied the effect of perinatal hypoxia in rats on brain NRG-1alpha protein levels. Seven-day-old rats were exposed to hypoxia versus air. Frontal-cortex levels of NRG-1alpha isoform were quantified at adulthood by Western blotting. Frontal-cortex NRG-1alpha was 32% elevated in hypoxia-exposed rats. The data support the role of non-genetic factors, e.g. oxygen restriction, in the expression of genes associated with schizophrenia.

Gene expression patterns in the hypoxic murine placenta: a role in epigenesis?

Hypoxia has been identified as a major stress or in placental and fetal development. To test the hypothesis that hypoxic stress responses are associated with gene expression changes, the authors measured gene expression in the mouse placenta in response to 48 hours of hypoxia. Embryonic day 15.5 pregnant mice were exposed to 48 hours of hypoxia (10.5% O(2)), after which the Affymetrix Mouse 430A_2.0 array was used to measure gene expression changes in the placenta. The authors observed 171 probe sets, corresponding to 163 genes, that were regulated by hypoxia (P < .01). Ninety genes were upregulated, and 73 were downregulated. The authors functionally annotated the regulated genes and examined overrepresented functional categories. Among the upregulated and downregulated genes, several overrepresented functional categories were observed. Upregulated genes included those involved in metabolism, oxygen transport, proteolysis, cell death, metabolism of reactive oxygen species, and DNA methylation. Genes involved in transcription, cell cycle regulation, and cell structure were downregulated. Microarray analysis has allowed the description of the genetic responses to hypoxia in the mouse placenta. The observation that hypoxia upregulates reactive oxygen species metabolism, in conjunction with DNA methylation enzymes, suggests that hypoxia may contribute to long-term epigenetic changes in stressed fetal tissues and organs.

Death effector activation in the subventricular zone subsequent to perinatal hypoxia/ischemia

Perinatal hypoxia/ischemia (H/I) is the leading cause of neurological injury resulting from birth complications and pre-maturity. Our studies have demonstrated that this injury depletes the subventricular zone (SVZ) of progenitors. In this study, we sought to reveal which cell death pathways are activated within these progenitors after H/I. We found that calpain activity is detected as early as 4 h of reperfusion and is sustained for 48 h, while caspase 3 activation does not occur until 8 h and peaks at 24 h post-insult. Activated calpains and caspase 3 co-localized within precursors situated in the lateral aspects of the SVZ (which coincides with progenitor cell death), whereas neither enzyme was activated in the medial SVZ (which harbors the neural stem cells that are resilient to this insult). These studies reveal targets for neuroprotective agents to protect precursors from cell death towards the goal of restoring normal brain development after H/I.

Immunohistochemical study of the morphological changes in placental villi from fetal membranes infectious disease

Many types of infection cause placental changes but sometimes the etiological cause may be difficult to prove. Infections may ascend from endocervical canal or they may reach placenta hematogenously through the maternal blood. Typically, placenta of "the amnionic sac infection syndrome" is an immature placenta. Complex cellular mechanisms are involved in all types of infection that often are associated with placental insufficiency.

OBJECTIVES

The aim of this study was to evaluate cellular changes induced by the hypoxic conditions due to infectious disease in the placental villous structures, especially in the trophoblast layer and vascular bed.

MATERIAL AND METHODS

In order to label the trophoblast layer we used anti-cytokeratin cocktail AE1/AE3. Antibodies anti-VEGF and anti-c-ErbB4 were used for the evaluation of tissue response under hypoxic conditions and its involvement in villous remodeling.

RESULTS

Chorion villi from placentas with histopathological features of insufficiency due to infectious etiology show an intense immunostaining for VEGF in the trophoblast, vessel walls and some stromal cells, namely Hofbauer cells. Villous trophoblast from the infected placenta expresses c-ErbB4 receptor.

CONCLUSIONS

Overexpression of VEGF and c-ErbB4 is needed for the involvement of trophoblast layer in villous remodeling processes in order to maintain placental functionality under the effects of the inflammatory cascade.