Antioxidant administration to the mother prevents oxidative stress associated with birth in the neonatal rat

Oxidative stress - Related spontaneous preterm delivery challenges in causality determination, prevention and novel strategies in reduction of the sequelae

Spontaneous preterm birth (PTB) is one of the major complications of pregnancy and the main cause of neonatal mortality and morbidity. Despite the efforts devoted to the understanding of this obstetrical syndrome and improved medical care, there has been a tendency for the PTB rate to increase in the last decades globally. The costs of the screening for spontaneous PTB, its management, and treatment of the sequelae represent a major burden to the health service economy of high-income countries. In this scenario, it has been widely acknowledged that oxidative stress (OS) plays an important role in the pathogenicity of human disease in wide range of areas of medicine. There is an emerging evidence that an imbalance between pro-and-antioxidants may be associated with spontaneous PTB. However, there are still many controversies on the mechanisms by which OS are involved in the pathogenesis of prematurity. Moreover, the crucial question whether the OS is the cause or consequence of the disease is yet to be answered. The purpose of this article is to briefly summarize the current knowledge and controversies on oxidative stress-related spontaneous PTB and to give a critical approach on future perspectives on this topic as a classical example of translational medicine. Placenta-mediated pregnancy adverse outcome associated with OS leading to iatrogenic PTB (e.g. pre-eclampsia, intrauterine growth restriction, gestational diabetes) will not be discussed.

Targeting Oxygen in Term and Preterm Infants Starting at Birth

Transition into the extrauterine world is characterized by a substantial increase in oxygen availability to tissue. Exact oxygen provision may be needed to avoid negative consequences of hypoxia or hyperoxia. For term and near-term infants, it is recommended to start with air and titrate the oxygen supplement to the saturation nomogram. However, oxygen supplementation in infants less than 32 weeks' gestation is an unsolved conundrum. At present, the inspired fraction of oxygen is set according to gestational age and blended to achieve targeted saturations and heart rates. Studies are still needed to overcome uncertainties about oxygen supplementation during preterm stabilization.

Hepatic 1-carbon metabolism enzyme activity, intermediate metabolites, and growth in neonatal Holstein dairy calves are altered by maternal supply of methionine during late pregnancy

Maternal supply of methyl donors such as methionine (Met) during late pregnancy can affect offspring growth and development. The objective was to investigate the effect of postruminal Met supply during late pregnancy on 1-carbon, Met cycle, and transsulfuration pathways in the calf liver. During the last 28 d of pregnancy, cows were individually fed a control diet or the control diet plus rumen-protected dl-Met (MET; 0.09% dry matter intake). Liver samples obtained from calves (n = 14/group) at 4, 14, 28, and 50 d of age were used for metabolomics, real-time PCR, and enzyme activity analyses. Genes associated with 1-carbon metabolism, DNA methylation, and the cytidine 5'-diphosphocholine-choline pathway were analyzed via real-time PCR. Activity of betaine homocysteine methyltransferase, cystathionine β-synthase, and 5-methyltetrahydrofolate homocysteine methyltransferase (MTR) was analyzed using ¹⁴C isotopes. Data were analyzed using a mixed model that included the fixed effects of maternal treatment, day, and their interaction, and the random effect was calf within maternal diet. Calves born to dams offered MET tended to have greater birth body weight and had overall greater body weight during the first 9 wk of life. However, no differences were detected for daily feed intake and average daily gain between groups. Concentrations of betaine and choline, reflecting Met cycle activity, at d 14 through 28 were greater in MET calves. Transsulfuration pathway intermediates also were altered in MET calves, with concentrations of cysteine sulfinic acid and hypotaurine (d 4 and 14) and taurine being greater (d 4, 14, 28, and 50). Despite the lack of differences in daily feed intake, the greater concentrations of the tricarboxylic acid cycle intermediates fumarate and glutamate along with NAD/NADH in MET calves indicated enhanced rates of energy metabolism. Although activity of betaine homocysteine methyltransferase was greater in MET calves at d 14, cystathionine β-synthase was lower and increased at d 14 and 28, where it was greater compared with the control diet. Activity of MTR was lower at d 4 and 50 in MET calves. Among gene targets measured, MET calves had greater overall expression of MTR, phosphatidylethanolamine N-methyltransferase, and choline kinase α and β. An interaction of maternal diet by time was detected for mRNA abundance of DNA methyltransferase 3α (involved in de novo methylation) due to greater values at d 4 and 14 in MET calves. Overall, the data indicate that enhanced postruminal supply of Met to cows during late pregnancy may program hepatic metabolism of the calf in the context of maintaining Met homeostasis, phosphatidylcholine and taurine synthesis, DNA methylation, and energy metabolism. These alterations potentially result in better efficiency of nutrient use, hence conferring the calf a physiologic advantage during a period of rapid growth and development. The precise biologic mechanisms remain to be established.

Oxidative Stress in the Newborn Period: Useful Biomarkers in the Clinical Setting

Aerobic metabolism is highly efficient in providing energy for multicellular organisms. However, even under physiological conditions, an incomplete reduction of oxygen produces reactive oxygen species and, subsequently, oxidative stress. Some of these chemical species are highly reactive free radicals capable of causing functional and structural damage to cell components (protein, lipids, or nucleotides). Oxygen is the most used drug in ill-adapted patients during the newborn period. The use of oxygen may cause oxidative stress-related diseases that increase mortality and cause morbidity with adverse long-term outcomes. Conditions such as prematurity or birth asphyxia are frequently treated with oxygen supplementation. Both pathophysiological situations of hypoxia⁻reoxygenation in asphyxia and hyperoxia in premature infants cause a burst of reactive oxygen species and oxidative stress. Recently developed analytical assays using mass spectrometry have allowed us to determine highly specific biomarkers with minimal samples. The detection of these metabolites will help improve the diagnosis, evolution, and response to therapy in oxidative stress-related conditions during the newborn period.

Oxidative Stress in the Developing Rat Brain due to Production of Reactive Oxygen and Nitrogen Species

Oxidative stress after birth led us to localize reactive oxygen and nitrogen species (RONS) production in the developing rat brain. Brains were assessed a day prenatally and on postnatal days 1, 2, 4, 8, 14, 30, and 60. Oxidation of dihydroethidium detected superoxide; 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate revealed hydrogen peroxide; immunohistochemical proof of nitrotyrosine and carboxyethyllysine detected peroxynitrite formation and lipid peroxidation, respectively. Blue autofluorescence detected protein oxidation. The foetuses showed moderate RONS production, which changed cyclically during further development. The periods and sites of peak production of individual RONS differed, suggesting independent generation. On day 1, neuronal/glial RONS production decreased indicating that increased oxygen concentration after birth did not cause oxidative stress. Dramatic changes in the amount and the sites of RONS production occurred on day 4. Nitrotyrosine detection reached its maximum. Day 14 represented other vast alterations in RONS generation. Superoxide production in arachnoidal membrane reached its peak. From this day on, the internal elastic laminae of blood vessels revealed the blue autofluorescence. The adult animals produced moderate levels of superoxide; all other markers reached their minimum. There was a strong correlation between detection of nitrotyrosine and carboxyethyllysine probably caused by lipid peroxidation initiated with RONS.

Changes in the Composition of Fatty Acids and Lipofuscin-Like Pigments During Development of Rat Heart

Postnatal heart development is characterized by critical periods of heart remodeling. In order to characterize the changes in the lipophilic fraction induced by free radicals, fatty acids and their oxidized products, lipofuscin-like pigments (LFP), were investigated. Fatty acids were analyzed by gas chromatography and LFP were studied by fluorescence techniques. A fluorophore characterized by spectral methods was further resolved by HPLC. Major changes in the composition of fatty acids occurred immediately after birth and then during maturation. Fluorescence of LFP changed markedly on postnatal days 1, 4, 8, and 14, and differed from the adult animals. LFP comprise several fluorophores that were present since fetal state till adulthood. No new major fluorophores were formed during development, just the abundances of individual fluorophores have been modulated which produced changes in the shape of the spectral arrays. HPLC resolved the fluorophore with excitation maximum at 360 nm and emission maximum at 410 nm. New chromatographically distinct species appeared immediately on postnatal day 1, and then on days 30 and 60. Consumption of polyunsaturated fatty acids immediately after birth and subsequent formation of LFP suggests that oxidative stress is involved in normal heart development.

Oxidative stress and tissue pathology caused by subacute exposure to ammonium acetate in rats and their response to treatments with alpha-ketoglutarate and N-acetyl cysteine

Ammonia is a widely used industrial chemical that is recognized as a potent neurotoxin and environmental pollutant. The present study addresses the oxidative stress and tissue pathology caused by 4 weeks of exposure to ammonium acetate (AMA; 100 mg/kg daily; orally) in rats, and their response to oral treatments with alpha-ketoglutarate (A-KG; 1.0 g/kg), a potential cyanide antidote, and/or N-acetyl cysteine (NAC; 10 mg/kg), an antioxidant. The organ-body weight index of brain and liver was significantly increased by AMA but kidney was unaffected. Also, plasma ammonia levels were significantly elevated without any concomitant change in blood gas status and hematology but levels of catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase and reduced glutathione (GSH) in the brain and liver were diminished, accompanied by elevated levels of malondialdehyde. Levels of glutathione disulfide (GSSG) were unaffected, but the ratio of GSH:GSSG was reduced. Plasma alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase and total bilirubin were raised but urea, uric acid and creatinine levels were not altered. AMA also caused temporal, hepatic and renal pathology. However, the renal pathology was not supported by any biochemical alterations. A-KG or NAC alone afforded less protection against AMA as compared to both given together. The protective efficacy of A-KG can be ascribed to its ability to detoxify ammonia and additionally both A-KG and NAC have antioxidant properties as well. The study suggests a new therapeutic regimen for ammonia poisoning.

Oxidative stress-induced formation of a positive-feedback loop for the sustained activation of p38 MAPK leading to the loss of cell division in cardiomyocytes soon after birth

Shortly after birth, mammalian cardiomyocytes irreversibly exit from the cell cycle and become terminally differentiated. The cellular mechanisms responsible for the cessation of cell division and terminal differentiation of cardiomyocytes soon after birth have intrigued developmental biologists as well as cardiovascular physicians, but the genetic cues for the irreversible exit from the cell cycle soon after birth remain largely unknown. We examined whether and if so how oxidative stress to mammalian hearts during fetal-neonatal transition produces changes in the proliferative activity and terminal differentiation of cardiomyocytes. Scavenging of reactive oxygen species (ROS) during fetal-neonatal transition, especially after birth, resulted in an increase in the proliferative activity and a decrease in the ratio of binucleated cardiomyocytes. Exposure to ROS in cultured cardiomyocytes increased the activity of p38 MAPK and the expression of connexin 43 (Cx43). Not only knockdown of Cx43 using siRNA but also the inhibition of p38 MAPK activity resulted in a significant decrease in the production of ROS in cardiomyocytes, suggesting that the signaling pathway ROS-p38 MAPK-Cx43 (especially, Cx43 at mitochondria, mtCx43) constituted a closed regulatory system with positive feedback. In addition, continuous scavenging of ROS or suppression of p38 MAPK activity for 4 days after birth resulted in a significant decrease in the expression of mtCx43 and in the number of binucleated cardiomyocytes. This study demonstrated that the ROS-induced formation of a positive-feedback loop ROS-p38 MAPK-mtCx43 for the sustained activation of p38 MAPK soon after birth possibly contributes to the loss of cell division and binucleation in mammalian cardiomyocytes.

Early postnatal development of rat brain is accompanied by generation of lipofuscin-like pigments

The increased generation of free radicals results in the formation of fluorescent end-products of lipid peroxidation, lipofuscin-like pigments (LFPs). The authors observed that LFPs are generated in rat brain after a normal birth during 5 postnatal days. The experimental design of the study comprised 10 groups of animals. The authors measured prenatal values 1 day and 7 days before birth, and then the animals were sampled on postnatal day 1, 2, 5, 10, 15, 25, 35, and 90. Maximum LFP concentration is achieved on the postnatal day 2. Starting from postnatal day 10, LFP concentration returns to prenatal values. A new rise in LFP concentration is observed at 3 months of age. This is associated with the beginning of the aging process. LFPs were characterized by fluorescence spectroscopy using tridimensional excitation spectra, synchronous spectra and their derivatives, and HPLC with fluorescence detection. It was possible to discern several tens of fluorescent compounds of unknown structure that are generated and metabolized during early development. The authors suggest that LFPs are formed after respiratory burst of microglia phagocytosing apoptotic cells.

Prenatal N-acetylcysteine prevents cigarette smoke-induced lung cancer in neonatal mice

Certain adult diseases may have their origin early in life, and perinatal exposures may contribute to cancers both during childhood and later in life. We recently demonstrated that mainstream cigarette smoke (MCS) induces a potent carcinogenic response in mice when exposure starts soon after birth. We also showed that the antioxidant N-acetylcysteine (NAC) prevents the extensive nucleotide and gene expression alterations that occur 'physiologically' at birth in mouse lung. The present study was designed to evaluate whether administration of NAC during pregnancy may affect the yield of tumors in mice exposed to MCS, starting after birth and continuing for 120 days. The results obtained showed that 210 days after birth, one adenoma only was detectable in sham-exposed mice. In contrast, as much as the 61.1% (33/54) of MCS-exposed mice born from untreated dams had lung tumors, including both benign tumors and bronchoalveolar carcinomas. Treatment with NAC during pregnancy strikingly inhibited the formation of benign lung tumors and totally prevented occurrence of carcinomas. In addition, prenatal NAC inhibited the MCS-induced hyperplasia of the urinary bladder epithelium. These findings demonstrate for the first time that treatment during pregnancy with an antioxidant chemopreventive agent can affect the induction of tumors consequent to exposure to a carcinogen after birth.

Human milk enhances antioxidant defenses against hydroxyl radical aggression in preterm infants

BACKGROUND

Preterm infants endowed with an immature antioxidant defense system are prone to oxidative stress. Hydroxyl radicals are very aggressive reactive oxygen species that lack specific antioxidants. These radicals cannot be measured directly, but oxidation byproducts of DNA or phenylalanine in urine are reliable markers of their activity. Human milk has a higher antioxidant capacity than formula.

OBJECTIVE

We hypothesized that oxidative stress associated with prematurity could be diminished by feeding human milk.

DESIGN

We recruited a cohort of stable preterm infants who lacked perinatal conditions associated with oxidative stress; were not receiving prooxidant or antioxidant drugs, vitamins, or minerals before recruitment; and were fed exclusively human milk (HM group) or preterm formula (PTF group). Collected urine was analyzed for oxidative bases of DNA [8-hydroxy-2'-deoxyguanosine (8-oxodG)/2'-deoxyguanosine (2dG) ratio] and oxidative derivatives of phenylalanine [ortho-tyrosine (o-Tyr)/Phe ratio] by HPLC coupled to tandem mass spectrometry. Healthy term newborn infants served as control subjects.

RESULTS

Both preterm groups eliminated greater amounts of metabolites than did the control group. However, the PTF group eliminated significantly (P < 0.02) higher amounts of 8-oxodG (8-oxodG/2dG ratio: 10.46 +/- 3.26) than did the HM group (8-oxodG/2dG ratio: 9.05 +/- 2.19) and significantly (P < 0.01) higher amounts of o-Tyr (o-Tyr/Phe ratio: 14.90 +/- 3.75) than did the HM group (o-Tyr/Phe ratio: 12.53 +/- 3.49). When data were lumped together independently of the type of feeding received, a significant correlation was established between the 8-oxodG/2dG and o-Tyr/Phe ratios in urine, dependent on gestational age and birth weight.

CONCLUSION

Prematurity is associated with protracted oxidative stress, and human milk is partially protective.

Oxidative stress mediated cytotoxicity of cyanide in LLC-MK2 cells and its attenuation by alpha-ketoglutarate and N-acetyl cysteine

Cyanide is a rapidly acting mitochondrial poison that inhibits cellular respiration and energy metabolism leading to histotoxic hypoxia followed by cell death. Cyanide is predominantly a neurotoxin but its toxic manifestations in non-neuronal cells are also documented. This study addresses the oxidative stress mediated cytotoxicity of cyanide in Rhesus monkey kidney epithelial cells (LLC-MK2). Cells were treated with various concentrations of potassium cyanide (KCN) for different time intervals and cytotoxicity was evidenced by increased leakage of intracellular lactate dehydrogenase, mitochondrial dysfunction (MTT assay) and depleted energy status of cells (ATP assay). Cytotoxicity was accompanied by lipid peroxidation indicated by elevated levels of malondialdehyde (MDA), reactive oxygen species (ROS) and reactive nitrogen species (RNS) (DCF-DA staining), diminished cellular antioxidant status (reduced glutathione (GSH), glutathione peroxidase, superoxide dismutase and catalase). These cascading events triggered an apoptotic kind of cell death characterized by oligonucleosomal DNA fragmentation and nuclear fragmentation (Hoechst 33342 staining). Apoptosis was further confirmed by increased caspase-3 activity. Cyanide-induced cytotoxicity, oxidative stress, and DNA fragmentation were prevented by alpha-ketoglutarate (A-KG) and N-acetyl cysteine (NAC). A-KG is a potential cyanide antidote that confers protection by interacting with cyanide to form cyanohydrin complex while NAC is a free radical scavenger and enhances the cellular GSH levels. The study reveals cytotoxicity of cyanide in cells of renal origin and the protective efficacy of A-KG and NAC.

Consequences of neonatal resuscitation with supplemental oxygen

There has been considerable controversy surrounding the optimal inspired oxygen concentration for resuscitation of term and preterm infants. We have developed a rat pup model to quantify both physiologic and biochemical parameters associated with normoxic vs. hyperoxic resuscitation. We have confirmed existing human data that hyperoxic resuscitation of rat pups is associated with a significant delay in onset of spontaneous respiratory efforts. Both 40% and 100% inspired oxygen delayed onset of respiratory activity when compared to 21% oxygen. We have also documented, in the rat pup model, that hyperoxic resuscitation is associated with reduced levels of glutathione at 24 hours post resuscitation. The implications of these and other findings for human infants are that term asphyxiated babies can be safely resuscitated in 21% oxygen and that supplementary oxygen can be reserved for non-responders. In contrast, resuscitation of extremely low gestational age infants does appear to require an initial low inspired oxygen concentration (eg, 30%) with subsequent pulse oximetry titration to optimize oxygenation status.

Achievement of targeted saturation values in extremely low gestational age neonates resuscitated with low or high oxygen concentrations: a prospective, randomized trial

OBJECTIVE

Extremely low gestational age neonates have very low oxygen saturation in utero and an immature antioxidant defense system. Abrupt increases in oxygen saturation after birth may cause oxidative stress. We compared achievement of a targeted oxygen saturation of 85% at 10 minutes of life when resuscitation was initiated with low or high fractions of inspired oxygen and levels were adjusted according to preductal pulse oxygen saturation values.

METHODS

A prospective, randomized, clinical trial was performed in 2 level III neonatal referral units. Patients of < or = 28 weeks of gestation who required active resuscitation were randomly assigned to the low-oxygen group (fraction of inspired oxygen: 30%) or the high-oxygen group (fraction of inspired oxygen: 90%). Every 60 to 90 seconds, the fraction of inspired oxygen was increased in 10% steps if bradycardia occurred (< 100 beats per minute) or was decreased in similar steps if pulse oxygen saturation reached values of > 85%. Preductal pulse oxygen saturation was continuously monitored.

RESULTS

The fraction of inspired oxygen in the low-oxygen group was increased stepwise to 45% and that in the high-oxygen group was reduced to 45% to reach a stable pulse oxygen saturation of approximately 85% at 5 to 7 minutes in both groups. No differences in oxygen saturation in minute-to-minute registers were found independent of the initial fraction of inspired oxygen used 4 minutes after cord clamping. No differences in mortality rates in the early neonatal period were detected.

CONCLUSIONS

Resuscitation can be safely initiated for extremely low gestational age neonates with a low fraction of inspired oxygen (approximately 30%), which then should be adjusted to the infant's needs, reducing the oxygen load to the neonate.

N-acetylcysteine protects melanocytes against oxidative stress/damage and delays onset of ultraviolet-induced melanoma in mice

PURPOSE

UV radiation is the major environmental risk factor for melanoma and a potent inducer of oxidative stress, which is implicated in the pathogenesis of several malignancies. We evaluated whether the thiol antioxidant N-acetylcysteine (NAC) could protect melanocytes from UV-induced oxidative stress/damage in vitro and from UV-induced melanoma in vivo.

EXPERIMENTAL DESIGN

In vitro experiments used the mouse melanocyte line melan-a. For in vivo experiments, mice transgenic for hepatocyte growth factor and survivin, shown previously to develop melanoma following a single neonatal dose of UV irradiation, were given NAC (7 mg/mL; mother's drinking water) transplacentally and through nursing until 2 weeks after birth.

RESULTS

NAC (1-10 mmol/L) protected melan-a cells from several UV-induced oxidative sequelae, including production of intracellular peroxide, formation of the signature oxidative DNA lesion 8-oxoguanine, and depletion of free reduced thiols (primarily glutathione). Delivery of NAC reduced thiol depletion and blocked formation of 8-oxoguanine in mouse skin following neonatal UV treatment. Mean onset of UV-induced melanocytic tumors was significantly delayed in NAC-treated compared with control mice (21 versus 14 weeks; P = 0.0003).

CONCLUSIONS

Our data highlight the potential importance of oxidative stress in the pathogenesis of melanoma and suggest that NAC may be useful as a chemopreventive agent.

A novel antioxidant N-acetylcysteine amide prevents gp120- and Tat-induced oxidative stress in brain endothelial cells

Free radical production and, consequently, oxidative stress play an important role in the pathogenesis of AIDS and cause damage to lipids, proteins, and DNA. In our previous study, the HIV-1 envelope glycoprotein (gp120) and transregulatory protein (Tat) of HIV-1 have been found to induce oxidative stress in an immortalized endothelial cell line from rat brain capillaries, RBE4 (in vitro model of the blood-brain barrier). Here, we have determined the effects of a novel antioxidant, N-acetylcysteine amide (NACA), on gp120- and Tat-induced oxidative stress. Various oxidative stress parameters, including reduced glutathione (GSH), oxidized glutathione (GSSG), catalase (CAT) activity, and glutathione reductase (GR) activity, as well as malondialdehyde (MDA) levels, were used as measures of oxidative stress. NACA significantly increased the levels of intracellular GSH, CAT, and GR and decreased the levels of MDA in RBE4 cells, showing that oxidatively challenged cells were protected. Gp120- and Tat-induced increases in intracellular reactive oxygen species (ROS) were observed by using the 2',7'-DCF assay; the ROS scavenger, NACA, blocked ROS generation. A well-known apoptosis indicator, caspase-3 activity, was measured and was also found to have been returned to its control levels by NACA. Treatment of RBE4 cells with gp120 and Tat caused an increase in toxicity, as measured by lactate dehydrogenase (LDH) and tetrazolium reduction (MTS) assays. HIV-1 protein-induced toxicity in these cells was blocked by treatment with NACA. These studies show that NACA reverses gp120- and Tat-induced oxidative stress in immortalized endothelial cells.

Phenytoin induced oxidative stress in pre- and postnatal rat development - effect of vitamin E on selective biochemical variables

A pre- and postnatal study was carried out to investigate the effect of high dose (500 mg/kg) of the natural antioxidant vitamin E (VIT E) on biochemical variables in the model of chronic intrauterine hypoxia. Chronic hypoxia was induced by administration of the anticonvulsant phenytoin (PHT) during pregnancy. Rats were orally treated with PHT (150 mg/kg) from day 7 to 18 of gestation and VIT E prior to PHT orally on the same days. The activity of the lysosomal enzyme N-acetyl-ss-D-glucosaminidase (NAGA) and the level of glutathione (GSH) were used as markers of tissue damage. In the prenatal study PHT-induced embryofoetal toxicity was associated with an increase in NAGA activity and decrease of GSH level in maternal serum and heart and with an increase in NAGA activity in the placenta. Administration of VIT E did not inhibit the above given changes. PHT increased the activity of NAGA and decreased the level of GSH in foetal organs (liver, lungs, brain). VIT E did not reverse these changes. In the postnatal study, we did not find any significant differences in NAGA activity in the organs of 1-day-old pups. An increase of liver GSH level was found in PHT and VIT E+PHT groups of pups and in the group VIT E+PHT in the lungs. In conclusion, supplementation with a high-dose of VIT E failed to protect maternal, foetal and new-born rat organs from PHT induced changes of selective biochemical variables.

Oxidative stress and apoptosis in fetal rat liver induced by maternal cholestasis. Protective effect of ursodeoxycholic acid

BACKGROUND/AIMS

The sensitivity of fetal rat liver to maternal obstructive cholestasis during pregnancy (OCP), and the effect of ursodeoxycholic acid (UDCA) were investigated.

METHODS

UDCA was administered (i.g. 0.6 mg/kg b.wt./day) from day 14 to day 21 of pregnancy after maternal common bile duct ligation.

RESULTS

Impairment in the activity of antioxidant enzymes, levels of total glutathione and GSH/GSSG ratio and the degrees of lipid peroxidation and protein carbonylation were similar in livers of OCP mothers and fetuses at term, despite hypercholanemia was milder in fetuses. Treatment of OCP rats with UDCA reduced maternal and fetal liver oxidative stress. Although maternal hypercholanemia was not corrected, fetal serum concentrations of major bile acids (except UDCA and beta-muricholic acid) were reduced. Fetal liver expression of key enzyme in bile acid synthesis, Cyp7a1, Cyp27 and Cyp8b1 was not affected by OCP or UDCA treatment. In OCP fetal livers, the relative expression of Bax-alpha and Bcl-2 and the activity of caspase-3, but not caspase-8, were increased. These changes were markedly reduced in fetuses of OCP animals treated with UDCA.

CONCLUSIONS

OCP induced moderate fetal hypercholanemia but marked liver oxidative stress and apoptosis that were partly prevented by treatment of pregnant rats with UDCA.

Resuscitation with 100% oxygen causes intestinal glutathione oxidation and reoxygenation injury in asphyxiated newborn piglets

OBJECTIVE

To compare mesenteric blood flow, oxidative stress, and mucosal injury in piglet small intestine during hypoxemia and reoxygenation with 21%, 50%, or 100% oxygen.

SUMMARY BACKGROUND DATA

Necrotizing enterocolitis is a disease whose pathogenesis likely involves hypoxia-reoxygenation and the generation of oxygen-free radicals, which are known to cause intestinal injury. Resuscitation of asphyxiated newborns with 100% oxygen has been shown to increase oxidative stress, as measured by the glutathione redox ratio, and thus may predispose to free radical-mediated tissue injury.

METHODS

Newborn piglets subjected to severe hypoxemia for 2 hours were resuscitated with 21%, 50%, or 100% oxygen while superior mesenteric artery (SMA) flow and hemodynamic parameters were continuously measured. Small intestinal tissue samples were analyzed for histologic injury and levels of oxidized and reduced glutathione.

RESULTS

SMA blood flow decreased to 34% and mesenteric oxygen delivery decreased to 9% in hypoxemic piglets compared with sham-operated controls. With reoxygenation, SMA blood flow increased to 177%, 157%, and 145% of baseline values in piglets resuscitated with 21%, 50%, and 100% oxygen, respectively. Mesenteric oxygen delivery increased to more than 150% of baseline values in piglets resuscitated with 50% or 100% oxygen, and this correlated significantly with the degree of oxidative stress, as measured by the oxidized-to-reduced glutathione ratio. Two of eight piglets resuscitated with 100% oxygen developed gross and microscopic evidence of pneumatosis intestinalis and severe mucosal injury, while all other piglets were grossly normal.

CONCLUSIONS

Resuscitation of hypoxemic newborn piglets with 100% oxygen is associated with an increase in oxygen delivery and oxidative stress, and may be associated with the development of small intestinal hypoxia-reoxygenation injury. Resuscitation of asphyxiated newborns with lower oxygen concentrations may help to decrease the risk of necrotizing enterocolitis.

Birth-related genomic and transcriptional changes in mouse lung

Birth is characterized by a sudden transition from the maternal-mediated respiration to the autonomous pulmonary respiration. Notwithstanding the importance of the involved functional and metabolic changes, little is known about possible DNA alterations occurring in the lung during the perinatal period. We comparatively evaluated genomic and transcriptional changes in the lung of fetuses and newborn Swiss albino mice, whose dams had either been untreated or treated with oral N-acetyl-L-cysteine (NAC) throughout the pregnancy period. In the less than 24h period elapsing between the end of fetal life and the start of post-natal life, nucleotide alterations occurred in mouse lung, as shown by a significant increase of both bulky DNA adducts and 8-hydroxy-2'-deoxyguanosine levels, detected by 32P post-labeling procedures. The frequency of micronuclei in peripheral blood erythrocytes was not significantly increased after birth. Multigene expression analysis of 746 selected genes, by cDNA arrays, showed that 33 of them (4.4%) were upregulated in the lung of newborn mice, as compared with fetuses. The overexpressed genes were mainly involved in protective mechanism as a response to oxidative changes, alterations of glutathione metabolism, cellular stress, and damage to DNA and proteins. The transplacental treatment with NAC totally prevented birth-related genomic alterations in lung DNA. NAC did not change the basal gene expression in mouse fetal lung, but attenuated the upregulation of most genes involved in oxidative stress, stress response, and DNA repair in the lung of newborn mice. In fact, only 13 genes (1.7%) were overexpressed in newborns from NAC-treated dams. It therefore appears that administration of NAC during pregnancy is beneficial not only to counteract the adverse effects of toxic agents, as supported by previous studies, but also to attenuate birth-related DNA alterations.

Oxidative stress in asphyxiated term infants resuscitated with 100% oxygen

OBJECTIVE

To test the hypothesis that resuscitation of asphyxiated infants with pure oxygen causes hyperoxemia and oxidative stress.Study design Asphyxiated term newborn infants (n = 106) were randomly resuscitated with room air (RAR = 51) or 100% oxygen (OxR = 55). The Apgar score, time of the first cry, and establishment of a sustained pattern of respiration were recorded. Assays performed included: blood gases; reduced glutathione (GSH) and oxidized glutathione (GSSG) in whole blood; glutathione-related enzyme activities; and superoxide dismutase activity (SOD) in erythrocytes.

RESULTS

The RAR group needed less time of ventilation for resuscitation (5.3 +/- 1.5 vs 6.8 +/- 1.2 min; P <.05). Pure oxygen caused hyperoxemia (PO(2), 126.3 +/- 21.8 mm Hg) that did not occur with the use of room air (PO(2), 72.2 +/- 6.8 mm Hg). GSH was decreased and GSSG, the glutathione cycle enzymes, and SOD activities were increased in both asphyxiated groups. However, the 100% oxygen-resuscitated group showed significantly greater alterations that correlated positively with hyperoxemia.

CONCLUSIONS

Asphyxia causes oxidative stress in the perinatal period, and resuscitation with 100% oxygen causes hyperoxemia and increased oxidative stress. Because there are no advantages to resuscitation with 100% oxygen, room air may be preferred under certain circumstances for the resuscitation of asphyxiated neonates.

Protective effect of N-acetylcysteine against fetal death and preterm labor induced by maternal inflammation

OBJECTIVE

Intrauterine and maternal systemic infections are proposed causes of preterm labor. The resulting prematurity is associated with 75% of infant mortality and 50% of long-term neurologic handicaps. We hypothesize that free radicals generated in large quantities during an inflammatory response shift the fetomaternal redox balance to an oxidative state, compromising the fetus. Thus, if our working hypothesis is correct, selective inactivation of free radicals with N-acetylcysteine (NAC), an antioxidant and glutathione (GSH) precursor, would improve the outcome of preterm deliveries associated with inflammation. We tested aspects of this hypothesis in an animal model of preterm labor and fetal damage (death).

STUDY DESIGN

NAC (1 g/kg) was administered orally to C57Bl/6 mice injected intraperitoneally with either 10 microg lipopolysaccharide (LPS) or saline solution (CRL) on day 16 of gestation. The latency period (time from injection to delivery of the first pup) and fetal viability were recorded. To discriminate between an effect of prematurity from an effect of inflammation, and to document any improvement in survival, mice were killed at 3, 6, and 16 hours after injection. Maternal and fetal redox states were approximated by measuring hepatic GSH.

RESULTS

Each C57Bl/6 LPS-treated mouse delivered prematurely after a significantly shorter latency period (LPS: 16.8 hours [95% CI 15.9-17.6] vs CRL: 54.7 hours [95% CI 43.8-65.5]). NAC doubled the latency interval of LPS-treated animals to 35.2 hours (95% CI 21.0-49.2). LPS alone resulted in a 100% rate of stillbirth. Fifty-eight percent of fetuses were already dead 16 hours after LPS. In contrast, only 33% of fetuses were dead 16 hours after LPS (P =.001) when NAC was given. LPS was followed by a reduction in maternal (LPS: 26.3 nmol/mg [95% CI 19.9-32.8] vs CRL: 41.3 nmol/mg [95% CI 34.7-47.9, P <.01]) and fetal GSH (LPS: 19.7 nmol/mg [95% CI 11.7-27.8] vs CRL: 34.5 nmol/mg [95% CI 32.0-37.0, P <.001]). This decline was reversed by NAC (NAC/LPS maternal GSH: 37.0 nmol/mg [95% CI 22.5-51.5] and fetal GSH: 28.4 nmol/mg [95% CI 22.8-33.9]). Importantly, maternal liver GSH impacted on fetal survival. NAC/LPS mothers with living pups 16 hours after LPS had significantly higher liver GSH compared with NAC/LPS mothers whose pups died in utero. In fact, all NAC-treated mice whose hepatic GSH exceeded 20 nmol/mg had living fetuses at 16 hours.

CONCLUSION

Maternal inflammation in C57Bl/6 mice results in oxidative stress associated with maternal and fetal GSH depletion. Oxidative stress damages the fetus independent of prematurity. Restoration of maternal and fetal oxidative balance by NAC protects the fetus and reduces the rate of preterm birth.

Hyperoxemia caused by resuscitation with pure oxygen may alter intracellular redox status by increasing oxidized glutathione in asphyxiated newly born infants

In a prospective, randomized, blinded trial we have studied the effects of resuscitation upon oxygenation in a group of asphyxiated newly born infants receiving room air or 100% oxygen as the gas source. During the acute phase of asphyxia and until the resuscitation procedure concluded, we determined serial blood gases as well as reduced and oxidized glutathione, enzymes involved in the glutathione redox cycle, and antioxidant enzyme activities. The use of 100% oxygen caused a remarkable increase of partial pressures of oxygen in arterial blood, with values that were frequently above physiological levels (> 100 mm Hg). In addition, we have found a significant correlation between hyperoxemia and the intra-erythrocyte GSSG (oxidized glutathione) concentration. We hypothesize that hyperoxemia may be 1 of the triggering factors responsible for an increased oxidation of GSH (reduced glutathione). Moreover, an increased antioxidant enzyme activity, which reflects an oxidative stress, indicates that the antioxidant capacity of the newly born infant may have been surpassed.

Six years of experience with the use of room air for the resuscitation of asphyxiated newly born term infants

In the last 6 years, 830 asphyxiated newly born term infants have been resuscitated with room air (RAR; n = 304) or 100% oxygen (OxR; n = 526) in our hospital. We have studied the time to onset of a regular respiratory pattern, morbidity and mortality, blood gases, reduced glutathione (GSH) and oxidised glutathione (GSSG) and antioxidant enzymes in these infants. No significant differences in the effectiveness of either gas sources or in the final outcome have been found. The RAR group required a shorter time of positive pressure ventilation to attain a spontaneous pattern of respiration. The OxR group showed hyperoxaemia during resuscitation, which was positively correlated with increased GSSG concentrations. Significant oxidative stress was found in the OxR group at 28 days of postnatal life when compared with normal control infants and the RAR group. Oxygen concentrations used during the resuscitation of newly born infants should be strictly monitored.

Resuscitation with room air instead of 100% oxygen prevents oxidative stress in moderately asphyxiated term neonates

BACKGROUND

Traditionally, asphyxiated newborn infants have been ventilated using 100% oxygen. However, a recent multinational trial has shown that the use of room air was just as efficient as pure oxygen in securing the survival of severely asphyxiated newborn infants. Oxidative stress markers in moderately asphyxiated term newborn infants resuscitated with either 100% oxygen or room air have been studied for the first time in this work.

METHODS

Eligible term neonates with perinatal asphyxia were randomly resuscitated with either room air or 100% oxygen. The clinical parameters recorded were those of the Apgar score at 1, 5, and 10 minutes, the time of onset of the first cry, and the time of onset of the sustained pattern of respiration. In addition, reduced and oxidized glutathione concentrations and antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase) were determined in blood from the umbilical artery during delivery and in peripheral blood at 72 hours and at 4 weeks' postnatal age.

RESULTS

Our results show that the room-air resuscitated (RAR) group needed significantly less time to first cry than the group resuscitated with 100% oxygen (1.2 +/- 0.6 minutes vs 1.7 +/- 0.5). Moreover, the RAR group needed less time undergoing ventilation to achieve a sustained respiratory pattern than the group resuscitated with pure oxygen (4.6 +/- 0.7 vs 7.5 +/- 1.8 minutes). The reduced-to-oxidized-glutathione ratio, which is an accurate index of oxidative stress, of the RAR group (53 +/- 9) at 28 days of postnatal life showed no differences with the control nonasphyxiated group (50 +/- 12). However, the reduced-to-oxidized-glutathione ratio of the 100% oxygen-resuscitated group (OxR) (15 +/- 5) was significantly lower and revealed protracted oxidative stress. Furthermore, the activities of superoxide dismutase and catalase in erythrocytes were 69% and 78% higher, respectively, in the OxR group than in the control group at 28 days of postnatal life. Thus, this shows that these antioxidant enzymes, although higher than in controls, could not cope with the ongoing generation of free radicals in the OxR group. However, there were no differences in antioxidant enzyme activities between the RAR group and the control group at this stage.

CONCLUSIONS

There are no apparent clinical disadvantages in using room air for ventilation of asphyxiated neonates rather than 100% oxygen. Furthermore, RAR infants recover more quickly as assessed by Apgar scores, time to the first cry, and the sustained pattern of respiration. In addition, neonates resuscitated with 100% oxygen exhibit biochemical findings reflecting prolonged oxidative stress present even after 4 weeks of postnatal life, which do not appear in the RAR group. Thus, the current accepted recommendations for using 100% oxygen in the resuscitation of asphyxiated newborn infants should be further discussed and investigated.

Effects of different diets and dietary restriction on perinatal endogenous DNA adducts. Time dependence of oxidative and presumptive nonoxidative lesions

Type II I-compounds (indigenous DNA adducts) denote a class of bulky oxidative DNA lesions that are detectable by 32P-postlabeling and represent useful biomarkers of DNA damage induced by oxidative stress. Their levels are increased in tissue DNA under pro-oxidant conditions, for example, as previously shown, in newborn rat organs. Here we have investigated whether the maternal diet affects perinatal type II I-compound levels. Pregnant F344 rats were fed Purina-5001 natural-ingredient or AIN-93G purified diet from day 11 of gestation. Type II I-compounds were measured in liver DNA at three different developmental stages, i.e., fetus, and 24 h and 9 days postnatally. Higher adduct levels were detected in the Purina-5001 group at each stage. In a second experiment, pregnant F344 rats were subjected to dietary restriction (DR) (by 40%; Purina-5001) from day 12 of gestation. At 24 h postpartum hepatic type II I-compound levels were decreased compared to parallel ad libitum (AL) fed controls. As an unrelated observation, fetal lung, but not liver, kidney, and skin DNA contained a different pattern of nonpolar, apparently nonoxidative adducts, which were not diet-dependent. These spots were not detectable 24 h after birth and were observed at much reduced levels and only in a few samples at 9 days. The main results show for the first time that the maternal nutrition modulated levels of oxidative lesions in fetal and neonatal DNA, but the underlying mechanisms (e.g., differences in metal or caloric content of the diets) still need to be determined. The dietary effects were apparently transmitted through both placenta and the mother's milk.

Glutathione and glutathione-related enzymes in reproduction. A review

Glutathione and glutathione-related enzymes are pivotal for the normal functioning of several important biological processes in humans. Glutathione and glutathione-related enzymes are involved in the metabolism and detoxification of cytotoxic and carcinogenic compounds as well as reactive oxygen species. The role of reactive oxygen species in reproduction was the subject of many investigations, and there is compelling evidence for the involvement of these species in the physiology and pathology of both male and female reproductive systems. The glutathione/glutathione-related enzyme system was extensively studied in gynaecological oncology, but to a lesser extent in other topics related to reproduction. In this paper a review is provided on the glutathione/glutathione-related enzyme system in reproduction. Attention is given to its role as a detoxicating system, and as an early marker for disease.

Necrogenic and regenerative responses of liver of newly weaned rats against a sublethal dose of thioacetamide

The hepatocellular necrogenic and regenerative responses of newly weaned rats (21 days old) to a sublethal dose of thioacetamide (6.6 mmol kg-1) were studied in comparison to adult (6-month old rats), in terms of liver injury, antioxidant defense systems and cell proliferation. Hepatocellular necrosis, detected by serum aspartate aminotransferase, was less severe in newly weaned rats than in adult animals and was parallel to previous changes in the activity of microsomal FAD monooxygenase system responsible for thioacetamide biotransformation. Liver damage in hepatocytes from newly weaned rats was also detected by the decreased levels of glutathione and protein thiol groups (47%, p < 0.001 and 52%, p < 0.001 vs. untreated, respectively) and by the enhanced malondialdehyde production (334%, p < 0.001) and glutathione S-transferase activity (384%, p < 0.001). No significant differences were detected in these values when compared to adults. Changes in cytosolic and mitochondrial superoxide dismutase and catalase activities in hepatocytes from newly weaned rats at 24 h, following thioacetamide (49%, p < 0.001; 50% and 53%, p < 0.001 vs. untreated, respectively), were less severe against those in adult hepatocytes at 48 h of intoxication, and the increases in glutathione peroxidase and glutathione reductase activities were significantly lowered: 25% (p < 0.001) and 41% (p < 0.001), respectively. Post-necrotic DNA synthesis in hepatocytes from newly weaned rats peaked at 48 h of intoxication, while in adults a more intense peak appeared at 72 h preceded by a sharp decrease in tetraploid population. These differences indicate that the lower necrogenic response against the same dose of thioacetamide in newly weaned rats may be due to the lower rate of thioacetamide biotransformation and to the earlier onset of cell division. Accordingly, the growing liver from newly weaned rats presents advantages against the necrogenic aggression of thioacetamide, first, because the diminished activity of its specific microsomal detoxification system, and second because the earlier increase in the proliferative response prevents the progression of injury permitting an earlier restoration of liver function.

Peroxidative and glutathione status in uterus and placenta after normal and pathological pregnancy

In 10 women with disturbed pregnancies without hypertension, reduced (GSH) and oxidized glutathione (GSSG) as well as lipid peroxides as thiobarbituric acid reactive substances (TBARS) were determined in the placenta and in the uterine tissue after unexpected stress-induced Caesarian section (group II). Production of TBARS was also measured in vitro in the 9000 x g supernatant of both tissues. The results were compared with those from women after normal pregnancy and expected Caesarian section (group I). After normal pregnancy higher TBARS and lower GSH with higher GSSG/GSH ratio were found in the placenta in comparison to the uterine tissue, indicating an oxidant/antioxidant imbalance in the placenta. No statistically significant differences were shown between the parameters of groups I and II. The possible oxidant stress associated with disturbed pregnancy and subsequent unexpected Caesarian section in this study was insufficient to alter tissue levels of glutathione nor the peroxidative status of placenta and uterus.

N-actylcysteine protects Chinese hamster ovary (CHO) cells from lead-induced oxidative stress

In vitro administration of lead acetate (PbA) to cultures of Chinese hamster ovary (CHO) cells had a concentration-dependent inhibitory effect on colony formation. Colony formation was returned to control levels in lead-treated cultures that were supplemented with 1 mM N-actylcysteine (NAC), a well-documented synthetic antioxidant. In order to investigate the nature of NAC's protective effect, we measured L-gamma-glutamyl-L-cysteinylglycine (GSH), oxidized glutathione (GSSG), malondialdehyde (MDA) and catalase activity both in the presence and absence of NAC in lead-exposed CHO cells. Increases in both MDA levels (p < 0.05) and catalase activity (P < 0.05) were observed in cultures that received only PbA, but supplementation with NAC returned these measures to pretreatment levels. The ratio of GSH to GSSG increased in lead-exposed cells incubated in NAC-enhanced media, but declined in cultures treated with PbA only. Our results suggest that NAC can confer protection against lead-induced oxidative stress to CHO cells, possibly through the enhancement of the cell's own antioxidant defense mechanisms.

In vivo indices of oxidative stress in lead-exposed C57BL/6 mice are reduced by treatment with meso-2,3-dimercaptosuccinic acid or N-acetylcysteine

Knowledge of lead's capacity to disrupt the prooxidant/antioxidant balance within mammalian tissues suggests that definitive therapy for chronic lead poisoning should encompass both chelating and antioxidant actions. The dithiol meso-2,3-Dimercaptosuccinic Acid (DMSA) is the first orally administered metal chelating agent to receive U.S. Food and Drug Administration (FDA) approval for the treatment of childhood plumbism and possesses the potential to function as an antioxidant by removing lead from the site of deleterious oxidation reactions. Five weeks of lead exposure was found to deplete glutathione (GSH) levels, increase oxidized glutathione (GSSG), and promote malondialdehyde (MDA) production in both liver and brain samples taken from C57BL/6 mice. GSH levels increased and GSSG and MDA levels decreased in groups of lead-exposed mice that received 1 mmol/kg DMSA or 5.5 mmol/kg N-acetylcysteine (NAC) for 7 d prior to sacrifice. Treatment with DMSA caused a reduction in blood, liver, and brain lead levels consistent with its function as a chelating agent, while treatment with NAC did not reduce these lead levels. However, NAC did cause a reduction in indices of oxidative stress in both brain and liver samples, which implies that this synthetic thiol-containing antioxidant is capable of abrogating lead-induced oxidative stress in vivo. Overall, these results suggest that lead-induced oxidative stress in vivo can be mitigated by pharmacologic interventions, which encompass both chelating as well as thiol-mediated antioxidant functions.