Chronic hypoxia alters cardiac mitochondrial complex protein expression and activity in fetal guinea pigs in a sex-selective manner

We hypothesize that intrauterine hypoxia (HPX) alters the mitochondrial phenotype in fetal hearts contributing to developmental programming. Pregnant guinea pigs were exposed to normoxia (NMX) or hypoxia (HPX, 10.5% O2), starting at early [25 days (25d), 39d duration] or late gestation (50d, 14d duration). Near-term (64d) male and female fetuses were delivered by hysterotomy from anesthetized sows, and body/organ weights were measured. Left ventricles of fetal hearts were excised and frozen for measurement of expression of complex (I-V) subunits, fusion (Mfn2/OPA1) and fission (DRP1/Fis1) proteins, and enzymatic rates of I and IV from isolated mitochondrial proteins. Chronic HPX decreased fetal body weight and increased relative placenta weight regardless of timing. Early-onset HPX increased I, III, and V subunit levels, increased complex I but decreased IV activities in males but not females (all P < 0.05). Late-onset HPX decreased (P < 0.05) I, III, and V levels in both sexes but increased I and decreased IV activities in males only. Both HPX conditions decreased cardiac mitochondrial DNA content in males only. Neither early- nor late-onset HPX had any effect on Mfn2 levels but increased OPA1 in both sexes. Both HPX treatments increased DRP1/Fis1 levels in males. In females, early-onset HPX increased DRP1 with no effect on Fis1, whereas late-onset HPX increased Fis1 with no effect on DRP1. We conclude that both early- and late-onset HPX disrupts the expression/activities of select complexes that could reduce respiratory efficiency and shifts dynamics toward fission in fetal hearts. Thus, intrauterine HPX disrupts the mitochondrial phenotype predominantly in male fetal hearts, potentially altering cardiac metabolism and predisposing the offspring to heart dysfunction.

Differential Expression of Endothelial Nitric Oxide Synthase in Coronary and Cardiac Tissue in Hypoxic Fetal Guinea Pig Hearts

OBJECTIVE

The purpose of the present study was to quantify the effect of chronic hypoxia on endothelial nitric oxide synthase (eNOS) gene and protein expression of fetal coronary artery segments and cardiac tissue of fetal guinea pig hearts.

METHODS

Time-mated pregnant guinea pigs (term = 65 days) were housed in room air (NMX, n = 6) or in a hypoxic chamber containing 10.5% O2 for 14 days (HPX14, n = 6). At near term (60 days gestation), fetuses were excised from anesthetized animals via hysterotomy and hearts were removed and weighed. Both coronary artery segments and cardiac ventricle were excised from the same hearts, frozen, and stored at -80 C until ready for study. eNOS mRNA was quantified using real-time polymerase chain reaction (PCR) based on SYBR Green I labeling (BioRad Laboratories, Hercules, CA) using eNOS primers obtained from GeneBank normalized to 18S. eNOS proteins were quantified by Western immunoblotting using eNOS antibody (1:200) and normalized to normoxic controls. eNOS cell-specific localization in the fetal guinea pig heart was performed by double immunofluorescence staining.

RESULTS

Both coronary artery endothelial cells (EC) and cardiomyocytes (CM) but not vascular smooth muscle cells of normoxic hearts exhibited positive immunostaining of eNOS protein. Chronic hypoxia significantly (P < .05) increased both eNOS mRNA and protein levels of coronary artery segments (by 210.6% and 51.4%, respectively) but decreased (P < .05) mRNA and protein of cardiac tissue (by 50.0% and 40.6%, respectively) in the same hearts.

CONCLUSIONS

Chronic fetal hypoxia, after 14 days, induces sustained changes in eNOS gene and eNOS protein expression that differ between coronary and cardiac tissue in the fetal guinea pig heart. This study suggests that while the functional roles of altered eNOS expression in hypoxic fetal hearts remain unclear, the site at which eNOS expression is altered may be important in the adaptive response of the fetal heart to hypoxia.

Partial neuroprotection by nNOS inhibition during profound asphyxia in preterm fetal sheep

Preterm brain injury is partly associated with hypoxia-ischemia starting before birth. Excessive nitric oxide production during HI may cause nitrosative stress, leading to cell membrane and mitochondrial damage. We therefore tested the hypothesis that therapy with a new, selective neuronal nitric oxide synthase (nNOS) inhibitor, JI-10 (0.022mg/kg bolus, n=8), given 30min before 25min of complete umbilical cord occlusion was protective in preterm fetal sheep at 101-104day gestation (term is 147days), compared to saline (n=8). JI-10 had no effect on fetal blood pressure, heart rate, carotid and femoral blood flow, total EEG power, nuchal activity, temperature or intracerebral oxygenation on near-infrared spectroscopy during or after occlusion. JI-10 was associated with later onset of post-asphyxial seizures compared with saline (p<0.05), and attenuation of the subsequent progressive loss of cytochrome oxidase (p<0.05). After 7days recovery, JI-10 was associated with improved neuronal survival in the caudate nucleus (p<0.05), but not the putamen or hippocampus, and more CNPase positive oligodendrocytes in the periventricular white matter (p<0.05). In conclusion, prophylactic nNOS inhibition before profound asphyxia was associated with delayed onset of seizures, slower decline of cytochrome oxidase and partial white and gray matter protection, consistent with protection of mitochondrial function.

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.

Chronic prenatal hypoxia induces epigenetic programming of PKC{epsilon} gene repression in rat hearts

RATIONALE

Epidemiological studies demonstrate a clear association of adverse intrauterine environment with an increased risk of ischemic heart disease in adulthood. Hypoxia is a common stress to the fetus and results in decreased protein kinase C epsilon (PKCepsilon) expression in the heart and increased cardiac vulnerability to ischemia and reperfusion injury in adult offspring in rats.

OBJECTIVES

The present study tested the hypothesis that fetal hypoxia-induced methylation of cytosine-phosphate-guanine dinucleotides at the PKCepsilon promoter is repressive and contributes to PKCepsilon gene repression in the heart of adult offspring.

METHODS AND RESULTS

Hypoxic treatment of pregnant rats from days 15 to 21 of gestation resulted in significant decreases in PKCepsilon protein and mRNA in fetal hearts. Similar results were obtained in ex vivo hypoxic treatment of isolated fetal hearts and rat embryonic ventricular myocyte cell line H9c2. Increased methylation of PKCepsilon promoter at SP1 binding sites, -346 and -268, were demonstrated in both fetal hearts of maternal hypoxia and H9c2 cells treated with 1% O(2) for 24 hours. Whereas hypoxia had no significant effect on the binding affinity of SP1 to the unmethylated sites in H9c2 cells, hearts of fetuses and adult offspring, methylation of both SP1 sites reduced SP1 binding. The addition of 5-aza-2'-deoxycytidine blocked the hypoxia-induced increase in methylation of both SP1 binding sites and restored PKCepsilon mRNA and protein to the control levels. In hearts of both fetuses and adult offspring, hypoxia-induced methylation of SP1 sites was significantly greater in males than in females, and decreased PKCepsilon mRNA was seen only in males. In fetal hearts, there was significantly higher abundance of estrogen receptor alpha and beta isoforms in females than in males. Both estrogen receptor alpha and beta interacted with the SP1 binding sites in the fetal heart, which may explain the sex differences in SP1 methylation in the fetal heart. Additionally, selective activation of PKCepsilon restored the hypoxia-induced cardiac vulnerability to ischemic injury in offspring.

CONCLUSIONS

The findings demonstrate a direct effect of hypoxia on epigenetic modification of DNA methylation and programming of cardiac PKCepsilon gene repression in a sex-dependent manner, linking fetal hypoxia and pathophysiological consequences in the hearts of adult offspring.

Prenatal hypoxia causes a sex-dependent increase in heart susceptibility to ischemia and reperfusion injury in adult male offspring: role of protein kinase C epsilon

The present study tested the hypothesis that protein kinase C (PKC) epsilon plays a key role in the sex dichotomy of heart susceptibility to ischemia and reperfusion injury in adult offspring resulting from prenatal hypoxic exposure. Time-dated pregnant rats were divided between normoxic and hypoxic (10.5% O(2) on days 15-21 of gestation) groups. Hearts of 3-month-old progeny were subjected to ischemia and reperfusion (I/R) injury in a Langendorff preparation. Preischemic values of left ventricle (LV) function were the same between control and hypoxic animals. Prenatal hypoxia significantly decreased postischemic recovery of LV function and increased cardiac enzyme release and infarct size in adult male, but not female, rats. This was associated with significant decreases in PKC(epsilon) and phospho-PKC(epsilon) levels in the LV of the male, but not female, rats. The PKC(epsilon) translocation inhibitor peptide (PKC(epsilon)-TIP) significantly decreased phospho-PKC(epsilon) in control male rats to the levels found in the hypoxic animals and abolished the difference in I/R injury observed between the control and hypoxic rats. In females, PKC(epsilon)-TIP inhibited PKC(epsilon) phosphorylation and decreased postischemic recovery of LV function equally well in both control and hypoxic animals. PKC(epsilon)-TIP had no effect on PKCdelta activation in either male or female hearts. The results demonstrated that prenatal hypoxia caused an increase in heart susceptibility to ischemia and reperfusion injury in offspring in a sex-dependent manner, which was due to fetal programming of PKC(epsilon) gene repression resulting in a down-regulation of PKC(epsilon) function in the heart of adult male offspring.

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.

Hypoxia blocks 11beta-hydroxysteroid dehydrogenase type 2 induction in human trophoblast cells during differentiation by a time-dependent mechanism that involves both translation and transcription

The present study was undertaken to determine (1) if hypoxia-induced down-regulation of placental 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2; encoded by HSD11B2 gene) activity and protein in human trophoblast cells during in vitro differentiation was mediated at the level of HSD11B2 gene transcription; and (2) whether the reduced placental 11beta-HSD2 in pregnancies complicated with fetal growth restriction (FGR) was a consequence of intrinsic abnormalities in trophoblast cells. Trophoblast cells were isolated from uncomplicated pregnancies and those complicated with FGR at term, and cultured for up to 72 h under normoxic (20% oxygen) or hypoxic (1% oxygen) conditions. Under normoxia, 11beta-HSD2 activity and protein increased progressively over the 72 h culture period, which was accompanied by a corresponding rise in 11beta-HSD2 mRNA. As demonstrated previously, hypoxia blocked the increase in levels of both 11beta-HSD2 activity and protein within the first 24h. In contrast, although hypoxia also prevented the rise in 11beta-HSD2 mRNA, it did not do so until 48 h. This time-dependent effect of hypoxia on placental 11beta-HSD2 activity/protein and mRNA suggests a dual mechanism of action whereby hypoxia may induce a rapid down-regulation of 11beta-HSD2 protein synthesis, which occurs initially at the level of translation, and later extends to the level of transcription. Indeed, transient transfection studies demonstrated that hypoxia diminished HSD11B2 promoter activity. When trophoblast cells isolated from FGR placentas were cultured and allowed to differentiate under the same conditions, they not only exhibited a similar pattern of 11beta-HSD2 activity and mRNA expression but also responded to hypoxia similarly to those from normal placentas. This suggests that the reduced placental 11beta-HSD2 in FGR is not due to intrinsic abnormalities in trophoblast cells, but likely a result of extrinsic factors associated with FGR.

Cellular levels of TrkB and MAPK in the neuroprotective role of BDNF for embryonic rat cortical neurons against hypoxia in vitro

Intrauterine asphyxia often results in neonatal loss or mental retardation. Brain-derived neurotrophic factor (BDNF) has been shown to be a protective agent against hypoxic damage to neurons. To understand the signaling mechanism underling the neuroprotective function of BDNF and to find therapeutic interventions for intrauterine asphyxia, we utilized an immunofluorescent technique to measure the intracellular levels of tyrosine kinase B (TrkB), phosphorylated TrkB, and the mitogen-activated protein kinase (MAPK) in the rat embryonic cortical neurons cultured in hypoxic conditions with and without BDNF pretreatment. The results showed that the fluorescent intensity of TrkB and phosphorylated TrkB in the cytoplasm and the fluorescent intensity of MARK in both cytoplasma and nucleus of the neurons were significantly increased in the presence of BDNF. The results indicate that the neuroprotective function of BDNF against hypoxia-induced neurotoxicity requires the participation of TrkB and is transduced via the Ras-MAPK signaling pathway.

cAMP response element-binding protein activation in ligation preconditioning in neonatal brain

Perinatal hypoxic-ischemic (HI) brain injury is a major cause of permanent neurological dysfunction in children. An approach to study the treatment of neonatal HI encephalopathy that allows for neuroprotection is to investigate the states of tolerance to HI. Twenty-four-hour carotid-artery ligation preconditioning established by delaying the onset of hypoxia for 24 hours after permanent unilateral carotid ligation rats markedly diminished the cerebral injury, however, the signaling mechanisms of this carotid-artery ligation preconditioning in neonatal rats remain unknown. Ligation of the carotid artery 24 hours before hypoxia provided complete neuroprotection and produced improved performance on the Morris water maze compared with ligation performed 1 hour before hypoxia. Carotid artery ligation 6 hours before hypoxia produced intermediate benefit. The 24-hour carotid-artery ligation preconditioning was associated with a robust and sustained activation of a transcription factor, the cAMP response element-binding protein (CREB), on its phosphorylation site on Ser133. Intracerebroventricular infusions of antisense CREB oligodeoxynucleotides significantly reduced the 24-hour carotid-artery ligation-induced neuroprotection effects by decreasing CREB expressions. Pharmacological activation of the cAMP-CREB signaling with rolipram 24 hours before hypoxia protected rat pups at behavioral and pathological levels by sustained increased CREB phosphorylation. This study suggests that 24-hour carotid-artery ligation preconditioning provides important mechanisms for potential pharmacological preconditioning against neonatal HI brain injury.

Umbilical plasma kininase I activity in fetal hypoxia

To shed light on the role of bradykinin in preeclampsia in addition to acute hypoxia, we measured the activity of kininase I, the enzyme responsible for its degradation, in umbilical plasma. Kininase I activity in umbilical arteries was compared with that in the umbilical veins. The relationship between kininase I and pH values was also evaluated in women with and without preeclampsia. Also, enzyme activity in supernatants of fetal hepatic cells (NFL/T) cultured under hypoxic or normoxic conditions were determined. Kininase I activity levels in fetal umbilical arteries and veins (n = 33) were similar (r = 0.77). Hypoxia caused suppression of kininase I activity in the supernatant cultures of NFL/T after one hour. However, after 8 and 24 hours, kininase I activity was significantly greater than under normoxic conditions (p < 0.05). Kininase I activity of fetal umbilical vein significantly decreased in the presence of acidemia in the uncomplicated group (n = 75, r = 0.42), whereas the activity negatively correlated with umbilical arterial pH in the preeclamptic group (n = 10, r = - 0.65). Kininase I activity levels in cases complicated with preeclampsia were significantly higher than without preeclampsia (49.2 +/- 9.1 vs. 66.2 +/- 11.3 nmol/ml/min). The present study indicates that kininase I acts as a regulatory factor in bradykinin degradation.

Prolonged mild fetal hypoxia up-regulates type I nitric oxide synthase expression in discrete areas of the late-gestation fetal sheep brain

OBJECTIVE

Our purpose was to study the effects of prolonged mild hypoxemia on type I nitric oxide synthase (NOS) messenger RNA, protein, and enzymatic activity in the fetal sheep brain.

STUDY DESIGN

Pregnant sheep were randomly allocated to receive maternal nitrogen (n = 8) or compressed air (controls, n = 5) to reduce fetal brachial artery PO(2) by 25% for 5 days. Type I NOS mRNA (determined by ribonuclease protection assay) protein (determined by Western blot) and enzymatic activity (determined by citrulline assay) were measured in the hippocampus, striatum, cerebellum, and frontal cortex. Data are presented as mean +/- SEM and were compared by means of one-way analysis of variance or two-sample t test.

RESULTS

The reduction in maternal inspired oxygen concentration decreased fetal PO(2) by 26% and oxygen content by 25% without an associated change in PCO(2) or pH. Fetal hypoxemia increased type I NOS mRNA by threefold in the striatum and by 2-fold in the frontal cortex and cerebellum, but it did not change mRNA expression in the hippocampus (P <.05). Type I NOS protein and catalytic activity increased only in the striatum (P <.05).

CONCLUSION

Prolonged mild hypoxemia has a differential effect on type I NOS mRNA in fetal sheep brain areas. Type I NOS protein and catalytic activity significantly increased only in the striatum. Our data suggest that fetal type I NOS gene expression is regulated at transcriptional, post-transcriptional, and translational levels.

[The activity of enzymes and free radical oxidation in acute and chronic fetal hypoxia in general anesthesia during cesarean section]

The following study dwells on a basic problem in obstetrics anaesthesia. It shows a present view of the in NLA and ataractics having effect on free radical oxygenation process in mother-fetus system in Cesarean section. 101 pregnant women have been studied as the values of FROq serum antioxygenase activityq serum enzymes activity in women blood and in blood of umbilical cord have been compared.

Tyrosine hydroxylase protein content in the medulla oblongata of the foetal sheep brain increases in response to acute but not chronic hypoxia

We have investigated the effect of lowering foetal arterial PO(2) either acutely or chronically on tyrosine hydroxylase (TH) protein content in the dorsal and ventral medullary regions of the brainstem of the sheep foetus during late gestation. TH protein content increased in both the dorsal and ventral medullary regions of the foetal brainstem after exposure to acute hypoxia when compared to normoxia. In contrast there was no increase in the TH protein content of either the dorsal or ventral medullary regions in the brainstem of foetal sheep which were chronically hypoxaemic throughout late gestation as a consequence of experimental restriction of placental growth. The differences between the TH responses to acute and chronic hypoxaemia in the foetal sheep brainstem may be important in the mediation of physiological adaptations to these intrauterine stimuli and for the generation of an appropriate physiological response to hypoxia in the newborn period.

Effect of gestational age and hypoxia on activity of ribonucleic acid polymerase in fetal guinea pig brain

OBJECTIVE

The aim of this study was to determine the effect of gestational age and hypoxia on the activity of ribonucleic acid polymerase in fetal guinea pig brain.

STUDY DESIGN

Fetal cerebral cortical neuronal nuclei were isolated at 40, 50, and 60 days (term) of gestation to determine the effect of gestational age on the activity of ribonucleic acid polymerase I, II, and III. Pregnant guinea pigs at 60 days' gestation were randomly assigned to a normoxic or hypoxic group to determine the effect of hypoxia on ribonucleic acid polymerase activity. The fetal neuronal nuclei were pooled from 6 pregnant animals in each group. In the normoxic group the pregnant guinea pigs were exposed to room air before delivery. In the hypoxic group delivery occurred after the pregnant guinea pig had been exposed to 7% oxygen for 60 minutes. The fetuses were delivered by cesarean, and the fetal cerebral cortical neuronal nuclei were isolated immediately. Ribonucleic acid polymerase activity was determined with nuclei suspended in a buffer containing adenosine triphosphate, guanosine triphosphate, cytidine triphosphate, and tritiated uridine triphosphate. Dactinomycin (actinomycin D) and polydeoxyadenylic-thymidylic acid were used to determine the activity of bound and free ribonucleic acid polymerase. alpha-Amanitin was used to determine the activity of ribonucleic acid polymerase II.

RESULTS

The activity of total (bound and free) ribonucleic acid polymerase I and III increased from 85.4 +/- 9.4 fmol of tritiated uridine triphosphate incorporated per milligram of protein per hour at 40 days' gestation to 233.3 +/- 82.1 fmol at 50 days and to 343.4 +/- 231.6 fmol at 60 days (P =.02). Total ribonucleic acid polymerase II activity increased from 19.9 +/- 6.0 fmol of tritiated uridine triphosphate incorporated per milligram of protein per hour at 40 days to 123.8 +/- 53.0 fmol at 50 days and to 200.9 +/- 77.8 fmol at 60 days (P <.01). In the term fetal guinea pig brain the activity of bound ribonucleic acid polymerase I and III decreased from 116.8 +/- 107.2 fmol of tritiated uridine triphosphate incorporated per milligram of protein per hour under normoxic conditions to 92.8 +/- 76.0 fmol in hypoxic fetal brain, a decrease of 20.5%. Free ribonucleic acid polymerase I and III activity decreased from 199.2 +/- 115.2 fmol of tritiated uridine triphosphate incorporated per milligram of protein per hour in normoxic fetal brain to 132.0 +/- 66.4 fmol in hypoxic fetal brain, a decrease of 33.8%. Free ribonucleic acid polymerase II activity decreased from 62.4 +/- 70.4 fmol of tritiated uridine triphosphate incorporated per milligram of protein per hour in normoxic fetuses to 13.6 +/- 9.6 fmol in hypoxic fetal brain, a decrease of 78.2%. In contrast, however, in term fetal guinea pig brain, bound ribonucleic acid polymerase II activity increased from 8.0 +/- 10.4 fmol of tritiated uridine triphosphate incorporated per milligram of protein per hour under normoxic conditions to 35.2 +/- 8.8 fmol in hypoxic fetal brain, an increase of 340% (P <.01).

CONCLUSION

The activity of ribonucleic acid polymerases I, II, and III increases throughout the latter half of gestation, from 40 to 60 days, in the fetal guinea pig brain. Hypoxia in utero is associated with a decrease in ribonucleic acid polymerase I and III activity. Although hypoxia is associated with a decrease in free ribonucleic acid polymerase II activity, we observed a marked increase in bound ribonucleic acid polymerase II activity, which may represent a hypoxia-induced alteration of gene expression.

Chronic hypoxia and developmental regulation of cytochrome c expression in rats

OBJECTIVE

To test the hypothesis that chronic hypoxia upregulates cytochrome c expression in heart, brain, and liver of fetal and maternal rats.

METHODS

Time-dated pregnant Sprague-Dawley rats were divided into normoxic and hypoxic (48 hours of 10.5% oxygen from days 19 to 21) groups, and were killed on day 21. Tissue levels of cytochrome c in heart, brain, and liver were determined by using monoclonal antiserum for cytochrome c.

RESULTS

Chronic hypoxia caused a decrease in fetal body weight (5.3 +/- 0.1 to 4.7 +/- 0.1 g) and an increase in heart/body weight ratio (0.0048 +/- 0.0001 to 0.0061 +/- 0.0002). Cytochrome c levels were 4-, 2.6-, and 13-fold higher in heart, liver, and brain, respectively, of the mother than of the fetus. Chronic hypoxia did not change cytochrome c levels in maternal tissues but caused a 70% increase and 54% decrease in cytochrome c levels in the fetal heart and liver, respectively. No difference was observed in the fetal brain.

CONCLUSIONS

The results suggest that expression of cytochrome c is tissue specific and developmentally regulated. Chronic hypoxia showed differential regulation of cytochrome c levels both developmentally and tissue specifically. The increased sensitivity of cytochrome c in fetal tissue to chronic hypoxia is likely to represent a fetal adaptive mechanism to the stress of chronic hypoxia.

Fetal and placental cyclic inositol phosphohydrolase in normoxia and hypoxia

Cyclic inositol phosphohydrolase (cIPH) converts cyclic inositol monophosphate (cIP), a putative modulator of cell growth, into inositol monophosphate. We hypothesized that hypoxic-ischemic injury alters cIPH activity in the placenta. On the 29th day of gestation pregnant rabbits were randomized to either 50 min of uterine ischemia (hypoxia) or no ischemia (controls). The activity of cIPH was measured by incubating with [3H]cIP and determining the release of [3H]inositol. Although no cIPH has been demonstrated in blood previously, cIPH activity was found in both fetal and maternal blood. cIPH activity was higher on the fetal side of the placenta than on the maternal side and was also higher in fetal blood compared to maternal blood. Hypoxia-ischemia failed to alter the cIPH activity in fetal blood and fetal and maternal placenta. Since cIPH activity is higher in the fetus and is retained even after major ischemia, modulation of cIP may be important in early development.

Reduced nitric oxide is involved in prenatal ischemia-induced tolerance to neonatal hypoxic-ischemic brain injury in rats

To explore the role of nitric oxide (NO) in the hypoxic-ischemic (HI) tolerance phenomenon, NO production and brain injury following neonatal hypoxia-ischemia (induced by unilateral common carotid artery ligation followed by hypoxic exposure) were assessed in rat pups with or without HI preconditioning. A previously demonstrated prenatal HI rat model of preconditioning was used in this study. On G17, rat fetuses were subjected to either HI in utero (PreHI) for 30 min or a sham operation (SH). The PreHI treatment provided significant protection against neonatal HI-induced brain injury, as indicated by decreased ipsilateral brain weight reduction, less severe tissue damage, and decreased activation of caspase-3. Concomitant with the protective effect of prenatal HI preconditioning, elevation of nitrite/nitrate content in the ipsilateral cortex of the brain, as an indirect measure of NO production, was significantly lower in the PreHI group than in the SH group following neonatal HI. The protective effect of prenatal HI preconditioning could be reversed by sodium nitroprusside (SNP), a spontaneous NO donor, while SNP had no effect on neonatal HI-induced brain injury in the SH group. Intraperitoneal administration of SNP to pups from the PreHI group (2 mg/kg, 24 and 1.5 h before neonatal HI) increased neonatal HI-induced brain injury similar to that observed in the SH group. On the other hand, L-N(G)-nitro-arginine (2 mg/kg, i.p., 1.5 h before the hypoxic exposure), an NO synthase inhibitor, significantly attenuated neonatal HI-induced brain injury in the SH group. The overall results indicate that reduced NO production in the preconditioned rat brain contributes to prenatal HI-induced tolerance to neonatal HI brain injury.

Hemodynamic and metabolic responses to moderate asphyxia in brain and skeletal muscle of late-gestation fetal sheep

The purpose of this study was to investigate metabolic and hemodynamic responses in two fetal tissues, hindlimb muscle and brain, to an episode of acute moderate asphyxia. Near-infrared spectroscopy was used to measure changes in total hemoglobin concentration ([tHb]) and the redox state of cytochrome oxidase (COX) simultaneously in the brain and hindlimb of near-term unanesthetized fetal sheep in utero. Oxygen delivery (DO(2)) to, and consumption (VO(2)) by, each tissue was derived from the arteriovenous difference in oxygen content and blood flow, measured by implanted flow probes. One hour of moderate asphyxia (n = 11), caused by occlusion of the maternal common internal iliac artery, led to a significant fall in DO(2) to both tissues and to a significant drop in VO(2) by the head. This was associated with an initial fall in redox state COX in the leg but an increase in the brain. [tHb], and therefore blood volume, fell in the leg and increased in the brain. These data suggest the presence of a fetal metabolic response to hypoxia, which, in the brain, occurs rapidly and could be neuroprotective.

Antioxidant role of endogenous coenzyme Q against the ischemia and reperfusion-induced lipid peroxidation in fetal rat brain

BACKGROUND

Ischemia and subsequent reperfusion induce lipid peroxidation in the cerebrum of the fetal rat. The present study evaluated the antioxidant activity of endogenous coenzyme Q in protecting against the lipid peroxidation induced in the fetal rat brain by ischemia/reperfusion.

METHODS

We used wistar rats at day 19 of pregnancy. Fetal ischemia was induced by bilateral occlusion of the utero-ovarian artery for 20 minutes. For reperfusion, the occlusion was released and the circulation was restored for 30 minutes. Control rats underwent sham operation. We determined the levels of thiobarbituric acid-reactive substances, the concentrations of coenzyme Q9, coenzyme Q10, and the mitochondrial respiratory control index in fetal brains.

RESULTS

Occlusion for 20 minutes significantly reduced the respiratory control index (p < 0.01), but did not alter the levels of thiobarbituric acid-reactive substances, coenzyme Q9 or coenzyme Q10. Subsequent reperfusion, however, significantly increased the level of thiobarbituric acid-reactive substances (from 6.53+/-1.54 to 11.46+/-3.31 nM/mg of protein, p < 0.01) and significantly decreased the level of coenzyme Q9 (from 291.73+/-108.94 to 162.44+/-56.83 pM/mg of protein, p < 0.05) and that of coenzyme Q10 (from 153.10+/-75.24 to 79.84+/-30.40 pM/mg of protein, p < 0.05). The respiratory control index was still significantly lower following reperfusion than in controls (p < 0.01). Significant negative correlations were observed between the level of thiobarbituric acid-reactive substances and the concentrations of either coenzyme Q9 (r = -0.68, p < 0.001) or coenzyme Q10 (r = -0.70, p < 0.001).

CONCLUSION

Endogenous coenzyme Q may protect the fetal rat brain against the lipid peroxidation induced by ischemia/reperfusion.

Chronic hypoxemia: effects on developing nitrergic and dopaminergic amacrine cells

PURPOSE

Very low birth weight and growth-restricted children have visual impairments including reduced contrast sensitivity, a parameter mediated in part by dopaminergic amacrine cells. The origin of these deficits is uncertain. In experimental fetal growth restriction, induced by placental insufficiency, the morphology and number of dopaminergic amacrine cells as identified by tyrosine hydroxylase staining were examined. In addition, the subclass of nitrergic amacrine cells was examined because nitric oxide released from nitric oxide synthase- containing neurons is proposed as a mediator of neurotoxicity and might contribute to the injury of dopaminergic amacrine cells in this situation.

METHODS

Fetal sheep were subjected to 20 or 30 days of placental embolization leading to fetal hypoxemia, hypoglycemia, and growth restriction during the last third of gestation (term, approximately 147 days). Retinal tissue was prepared as wholemounts or cryostat sections and analyzed for retinal area, total number, density, somal size and cell process length of amacrine cells immunoreactive for tyrosine hydroxylase or nitric oxide synthase, and widths of retinal layers. Retinas from fetal sheep at 72, 96, 113, and 140 days' gestation and adults were collected for an ontogenetic study of tyrosine hydroxylase-immunoreactive neurons.

RESULTS

In growth-restricted fetuses, the number of tyrosine hydroxylase-immunoreactive neurons and the total length of stained processes per cell were significantly reduced compared to control fetuses. The total number of neuronal nitric oxide synthase- containing neurons was not different between growth-restricted and control fetuses. The thickness of the inner retinal layers was reduced in hypoxemia.

CONCLUSIONS

There is damage to tyrosine hydroxylase-immunoreactive amacrine cells during fetal chronic placental insufficiency. This damage might be involved in the altered retinal dopaminergic system observed in very low birth weight infants, some of whom are growth-restricted. Furthermore, a differential susceptibility of tyrosine hydroxylase-immunoreactive and neuronal nitric oxide synthase-containing amacrine cells to hypoxemic injury has been demonstrated. These observations add to the current hypothesis that neuronal nitric oxide synthase- containing neurons are resistant to hypoxemic injury and may be involved in mediating some of the neuronal damage that results from hypoxemic insults.

Developmental changes of gene expression in heme metabolic enzymes in rat placenta

Transcription levels of the non-specific delta-aminolevulinate synthase (ALAS-N) and heme oxygenase-1 (HO-1) in the placenta at the terminal stage of pregnancy were comparable to those in the female adult liver and in the spleen, respectively. Immunohistochemical studies demonstrated that both enzymes were exclusively expressed in the trophoblast. During gestation, transcript of ALAS-N slightly increased, while HO-1 mRNA significantly decreased. Induced acute fetal hypoxia resulted in an increase in ALAS-N mRNA and in a decrease in HO-1 mRNA. These findings indicate that placental heme metabolism is influenced by the oxygen supply.

Lipid peroxidation and superoxide dismutase activity in umbilical and maternal blood

Oxygenation of both mother and child tissues oscillate frequently during labour. We tested the lipid peroxidation caused by reactive oxygen species which are produced in consequence of tissue reoxygenation and the inactivation of these species by the maternal and newborn superoxide dismutase. Total malondialdehyde in concentrations (mean +/- SE) of 1.04 +/- 0.17, 1.57 +/- 0.22, 1.33 +/- 0.14 and 1.36 +/- 0.21 mumol/L was found in maternal plasma and red blood cells and newborn plasma and red blood cells, respectively, after uncomplicated deliveries and 4.93 +/- 1.34, 7.12 +/- 1.37, 4.77 +/- 1.29 and 7.37 +/- 1.51 mumol/L, respectively, after deliveries with clinical signs of foetal hypoxia. In newborns, erythrocyte superoxide dismutase activity reached only 82% of the maternal level (p < 0.05). The results indicate that the maternal and foetal antioxidant defence systems can be overloaded during deliveries with abnormal oxygenation, where increased lipid peroxidation occurred.

Measurement of fetal plasma levels of glutathione S-transferase B1 as an indicator of damage to the liver caused by hypoxia in utero

Glutathione S-transferase B1 (GST B1) concentration in blood and amniotic fluid from fetuses investigated for a variety of conditions including rhesus (Rh) allo-immunisation was assessed for its usefulness as a measure of liver damage caused by hypoxia in utero. The concentration in blood from the intrahepatic vein (IHV) was 10-fold higher than that from the placental cord insertion suggesting that parenchymal liver cells are damaged during blood sampling from the IHV. As a measure of hepatocellular impairment caused by intra-uterine hypoxia, levels were higher in frankly acidotic fetuses than in normally managed Rh fetuses. The degree of hypoxia required to trigger the release of GST B1 into the plasma remains unclear.

Ornithine decarboxylase activity in fetal and newborn rat brain: responses to hypoxic and carbon monoxide hypoxia

In response to acute maternal hypoxia, ornithine decarboxylase (ODC) activity increased significantly in fetal rat brain, peaking at 4 h. This was associated with increased ODC mRNA and elevated polyamine concentrations. To correlate this response with development, we measured ODC activity in the rat from gestational day E 17 to postnatal day P 10. We also examined to what extent hypoxia induces increased ODC activity in adult rat brains and whether the response to chronic hypoxia differed from that to acute hypoxia. To test the hypothesis that this increased activity is due to hypoxic hypoxia per se, we subjected pregnant dams to inspired carbon monoxide concentrations ranging from 150 to 1000 ppm and assayed ODC activity in the fetal brain 4 h later. In the fetus, ODC activity was elevated on E 17 in the cerebrum and cerebellum. It declined gradually to about one-tenth E 17 levels by E 21 and remained low thereafter except for a postnatal elevation in the cerebellum on P 3. In response to 10.5% O2, in the 3-day-old rat, ODC activity peaked between 2 and 3 h of hypoxia, increasing 3-fold in the hippocampus and 2-fold in cerebellum. Similar increases were seen in the hypoxic adult rat brain. In inspired oxygen dose-response studies, exposure of P 3 rat pups to 13.25% O2 for 2.5 h produced a 1.5-fold increase in ODC activity; 10.5% O2 produced a 2-3-fold increase while in response to 9% O2, ODC activity remained at baseline levels. With maternal CO-hypoxia, ODC activity increased in the fetal brain at 4 h, as seen with hypoxic-hypoxia. For example, in hippocampus, ODC activity doubled at 500 ppm and tripled at 600 ppm. We conclude: (1) apparently, the ability to respond thus is not lost as the animal ages and may represent an important cellular response to acute hypoxia; (2) the increase in hypoxic-induced ODC activity is relative to the already elevated activity seen from E 17 to E 20; a vast reserve for the induction of fetal ODC activity probably exists and may indicate the importance of this enzyme during this time frame for differentiation and growth promotion; and (3) the CO-hypoxia studies suggest that some aspects of the cellular responses to CO- and hypoxic-hypoxia are similar.

Group I and group II phospholipase A2 in serum during normal and pathological pregnancy

Phospholipase A2 groups I (pancreatic) and II (synovial) could be a link between local and systemic changes in pregnancy, reflected in catalytic activity. We studied whether normal pregnancy, preeclampsia, preterm labor and four other diseases have processes involving serum phospholipase A2s. Pancreatic and synovial-type phospholipase A2 were measured in the serum of 59 normal pregnant women and 89 patients with pathological pregnancy by newly developed time-resolved fluoroimmunoassays, and the catalytic activity by a radiochemical method using micellar phosphatidylcholine as substrate. During pregnancy weeks 6-14, synovial-type phospholipase A2 and catalytic activity were elevated 2- to 4-fold, but at 37 weeks values were normal. Pregnancy-induced hypertensive diseases increased by 4- to 10-fold the concentration of synovial-type phospholipase A2, reflected in catalytic activity. In 8 out of 14 cases, the enzyme was increased if the fetus was to be delivered prematurely. The enzymes studied remained within the reference interval in cases of hepatogestosis, fetal asphyxia, diabetes and twin pregnancy. Newly developed specific immunoassays for measuring different types of phospholipase A2 in serum can provide insights for clinical follow-up.

Hypoxic risk in twins assessed by serum creatinine kinase brain isoenzyme measurement

A marked intrapair discordance in placentas and in many body and organ measurements are risk factors influencing perinatal mortality and morbidity in twins. Asphyxia is the single most important perinatal cause of neurologic morbidity in newborn infants. The higher hypoxic risk for the second twin arises, however, from conclusions based on studies that did not consider the new diagnostic possibility of using blood measurements of the brain-type isoenzyme of creatine kinase (CK-BB) as a marker of perinatal asphyxia. CK-BB levels were measured in cord blood of 60 preterm infants (mean birth weight 1670 +/- 390 g, and mean gestational age 33 +/- 1.9 weeks) born of twin gestation in the last 3 years. The mean CK-BB values were 48 +/- 40 U/l versus 29 +/- 31 U/l (p less than 0.5). Skilful antepartum and perinatal care are the keys for optimal management of both babies, as demonstrated by similar CK-BB values obtained in their cord-blood specimens after birth.

[Changes in the lactate dehydrogenase isoenzyme activity in parturients with chronic fetal hypoxia during different types of anesthesia in surgical delivery]

During cesarean delivery, the isoenzymic spectrum of lactate dehydrogenase and lactic acid levels were examined in 109 parturients with chronic fetal hypoxia. For initial anesthesia, sombrevin, kalipsol, hexenal were applied, basal anesthesia was performed with neuroleptic analgetics and combined electric anesthesia. The findings make it possible to choose the optimal anesthetic agents in this group of parturients in order to make the status of a fetus and a neonate stable and better.

5'-Nucleotidase and adenosine deaminase in developing fetal guinea pig brain and the effect of maternal hypoxia

The activity of key enzymes of adenosine metabolism was studied in the developing fetal guinea pig brain. The activities of 5'-nucleotidase and adenosine deaminase were determined in the brains of fetal guinea pigs at 30, 35, 40, 45, 50, 55, and 60 days of gestation. The level of 5'-nucleotidase activity was extremely low at 30 and 35 days of gestation but increased rapidly during the 40 to 60 day period. The enzyme activity increased in the presence of Mg2+ with the Mg2+ - dependent activation increasing with the age of gestation. This Mg2+ - dependent activity was primarily associated with the membrane fraction. Prenatal hypoxia significantly increased the fetal brain M2+ - independent 5'-nucleotidase activity at 45 days of gestational age and beyond. Prior to this age, no effect was evident. Furthermore, following hypoxia, the Mg2+ - dependent activation of 5'-nucleotidase activity was lost. The activity of adenosine deaminase was present at 30 days of gestation and, unlike 5'-nucleotidase, it remained at the same level until 60 days. The results indicate that the term fetal guinea pig brain has the enzymatic mechanisms of adenosine metabolism and thus the potential for adenosine-mediated regulation of cerebrovasculature during hypoxia.

Developmental profiles of catecholaminergic enzymes in adrenals of perinatal rats: effect of a hypoxic environment

Fetal and early neonatal development of adrenal catecholaminergic enzymes was studied in rats maintained under normal (normoxic) and high-altitude, 3800 m, 13% PO2 (hypoxic) conditions. In adrenals of normoxic fetuses, tyrosinehydroxylase (TH), DOPA-decarboxylase (DDC), phenylethanolamine-N-methyltransferase (PNMT), catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) showed rapid increases in activity from day 19 to day 21 of gestation. The activities of all enzymes but TH were higher at day 1 postpartum compared to fetal values: TH was equiactive just before and after birth. In animals conceived, born and raised at high altitude, several changes indicative of impaired adrenal development occurred. The activities of the synthesizing enzymes, TH, DDC and PNMT, were variably affected at some time during the perinatal period. The activities of the catabolizing enzymes, MAO and COMT, at high altitude were increased on the last days of gestation but depressed after birth, compared to control levels. Catecholamine content in high-altitude adrenals was altered on day 19 of gestation when epinephrine was lower, and again on day 1 postpartum when both norepinephrine and epinephrine were higher than in control adrenals at sea level. Normal developmental changes and high-altitude-induced disturbances in adrenal catecholaminergic enzymes are discussed with reference to differences observed in adrenal cortical function between sea-level and high-altitude animals.

Perinatal changes in glycolytic function in response to hypoxia in the incubated or perfused rat heart

Glycolysis was assessed in the rat heart during the perinatal period: in the fetus of 16.5 days postcoitum (dpc) and 21.5 dpc (term = 22 dpc) and in the newborn of 1 day postpartum (dpp) and 7 dpp. Glucose uptake, lactate production and glucose incorporation into glycogen were much higher in the fetal than in the newborn heart. Measurements were made of tissue contents of high energy phosphate compounds, lactate and hexose phosphates. Unchanged contents of glucose-6-phosphate and fructose-6-phosphate during hypoxia in spite of an increased flux through the enzyme phosphofructokinase (PFK) suggest that PFK has a regulatory role in the glycolysis as early as 16.5 dpc. The isolated fetal heart was more resistant to hypoxia than the newborn heart: glucose uptake and lactate production were much higher and high energy phosphate compounds and glycogen were better maintained in the fetal heart.

[Effect of alpha-glycerophosphate on intracellular distribution of hexokinase in the tissue of fetal rabbits during acute hypoxia]

In experiments with 40 rabbit fetuses acute intrauterine hypoxia caused a redistribution of the hexokinase activity in brain and liver tissues towards an increase in the amount of the enzyme associated with mitochondria. Previous administration of alpha-glycerophosphate into rabbit female (at a dose of 1.3 g/kg of body weight) was accompanied by an increase in the hexokinase activity in liver mitochondria and in brain cytoplasmic fraction of fetus as well as in the total homogenate of both tissue. The phenomenon might be considered as a positive pattern in adaptation to hypoxia.

[Histoenzymologic modifications of placental tissue in experimental fetal hypotrophy in the rat]

Chronic placental vascular insufficiency in the rat was achieved by ligature of the uterine and utero-placental arteries. The fetal and placental hypotrophy observed confirmed the previous observation. However, the placental enzymatic changes showed an increasing gradient of cellular hypoxy from decidua basalis to yolk sac placenta; this gradient is unfavourable to fetuses. The strong depletion of yolk sac enzyme activities demonstrates the reduction of fetomaternal exchanges which are usually predominant in this placental area. The other parts of rat placenta appear relatively less involved in fetal nutrition. Further studies are necessary to understand the changes observed in these activity stainings, such as: oxidoreductases II, acid phosphatase and 5-nucleotidase.