Moderate ethanol exposure during early ontogeny of the rat alters respiratory plasticity, ultrasonic distress vocalizations, increases brain catalase activity, and acetaldehyde-mediated ethanol intake

Early ontogeny of the rat (late gestation and postnatal first week) is a sensitive period to ethanol’s positive reinforcing effects and its detrimental effects on respiratory plasticity. Recent studies show that acetaldehyde, the first ethanol metabolite, plays a key role in the modulation of ethanol motivational effects. Ethanol brain metabolization into acetaldehyde via the catalase system appears critical in modulating ethanol positive reinforcing consequences. Catalase system activity peak levels occur early in the ontogeny. Yet, the role of ethanol-derived acetaldehyde during the late gestational period on respiration response, ultrasonic vocalizations (USVs), and ethanol intake during the first week of the rat remains poorly explored. In the present study, pregnant rats were given a subcutaneous injection of an acetaldehyde-sequestering agent (D-penicillamine, 50 mg/kg) or saline (0.9% NaCl), 30 min prior to an intragastric administration of ethanol (2.0 g/kg) or water (vehicle) on gestational days 17–20. Respiration rates (breaths/min) and apneic episodes in a whole-body plethysmograph were registered on postnatal days (PDs) 2 and 4, while simultaneously pups received milk or ethanol infusions for 40-min in an artificial lactation test. Each intake test was followed by a 5-min long USVs emission record. On PD 8, immediately after pups completed a 15-min ethanol intake test, brain samples were collected and kept frozen for catalase activity determination. Results indicated that a moderate experience with ethanol during the late gestational period disrupted breathing plasticity, increased ethanol intake, as well brain catalase activity. Animals postnatally exposed to ethanol increased their ethanol intake and exerted differential affective reactions on USVs and apneic episodes depending on whether the experience with ethanol occur prenatal or postnatally. Under the present experimental conditions, we failed to observe, a clear role of acetaldehyde mediating ethanol’s effects on respiratory plasticity or affective states, nevertheless gestational acetaldehyde was of crucial importance in determining subsequent ethanol intake affinity. As a whole, results emphasize the importance of considering the participation of acetaldehyde in fetal programming processes derived from a brief moderate ethanol experience early in development, which in turn, argues against “safe or harmless” ethanol levels of exposure.

Multi-biomarker approach to evaluate the neurotoxic effects of environmentally relevant concentrations of phenytoin on adult zebrafish Danio rerio

Several studies have reported the presence of phenytoin (PHE) in wastewater treatment plant effluents, hospital effluents, surface water, and even drinking water. However, published studies on the toxic effects of PHE at environmentally relevant concentrations in aquatic organisms are scarce. The present study aimed to determine the effect of three environmentally relevant concentrations of PHE (25, 282, and 1500 ng L^-1) on behavioral parameters using the novel tank test. Moreover, we also aimed to determine whether or not these concentrations of PHE may impair acetylcholinesterase (AChE) activity and oxidative status in the brain of Danio rerio adults. Behavioral responses suggested an anxiolytic effect in PHE-exposed organisms, mainly observed in organisms exposed to 1500 ng L^-1, with a significant decrease in fish mobility and a significant increase in activity at the top of the tank. Besides the behavioral impairment, PHE-exposed fish also showed a significant increase in the levels of lipid peroxidation, hydroperoxides, and protein carbonyl content compared to the control group. Moreover, a significant increase in brain AChE levels was observed in fish exposed to 282 and 1500 ng L^-1. The results obtained in the present study show that PHE triggers a harmful response in the brain of fish, which in turn generates fish have an anxiety-like behavior.

Glucose-6-Phosphate Dehydrogenase, Redox Homeostasis and Embryogenesis

Normal embryogenesis requires complex regulation and precision, which depends on multiple mechanistic details. Defective embryogenesis can occur by various mechanisms. Maintaining redox homeostasis is of importance during embryogenesis. NADPH, as produced from the action of glucose-6-phosphate dehydrogenase (G6PD), has an important role in redox homeostasis, serving as a cofactor for glutathione reductase in the recycling of glutathione from oxidized glutathione and for NADPH oxidases and nitric oxide synthases in the generation of reactive oxygen (ROS) and nitrogen species (RNS). Oxidative stress differentially influences cell fate and embryogenesis. While low levels of stress (eustress) by ROS and RNS promote cell growth and differentiation, supra-physiological concentrations of ROS and RNS can lead to cell demise and embryonic lethality. G6PD-deficient cells and organisms have been used as models in embryogenesis for determining the role of redox signaling in regulating cell proliferation, differentiation and migration. Embryogenesis is also modulated by anti-oxidant enzymes, transcription factors, microRNAs, growth factors and signaling pathways, which are dependent on redox regulation. Crosstalk among transcription factors, microRNAs and redox signaling is essential for embryogenesis.

Malformations and mortality in zebrafish early stages associated with elevated caspase activity after 24 h exposure to MS-222

Tricaine methanesulfonate (MS-222) is a commonly used anaesthetic agent for immobilization of aquatic species. However, delayed development and malformations have been observed in 24 hpf (hours post-fertilization) zebrafish embryos after long-term immobilization. Still, no comprehensive study has been described regarding zebrafish exposure to MS-222 during the first hours of development, which are one of the most sensitive life stages to toxicants. Therefore, this research aimed to assess the toxicity of a 24 h exposure to MS-222 on zebrafish embryonic development. Based on the MS-222 LC₅₀, early blastula stage embryos (~2 hpf) were exposed to 0, 12.5, 25 and 50 mg L^-1 for 24 h and then allowed to develop up to 144 hpf. The chromatographic analysis showed that this anaesthetic agent bioaccumulates in 26 hpf zebrafish larvae in a concentration-dependent manner. In addition, increased mortalities and skeletal abnormalities were observed at 144 hpf, namely in the highest tested concentration. Yet, no craniofacial anomalies were observed either by alcian blue or calcein staining methods. Independently of the tested concentration, decreased speed and distance travelled were perceived in 144 hpf larvae. At the biochemical level, decreased in vivo reactive oxygen species (ROS) generation and apoptosis was observed. Additionally, catalase activity was increased at 26 hpf while results of mRNA expression showed a decreased gclc transcript content at the same time-point. Overall, data obtained highlight the toxicological risk of MS-222 and support ROS-mediated cell death signalling changes through the elevation of catalase activity as an adaptative or protective response.

Advances in BPA-induced Oxidative Stress and Related Effects and Mechanisms in Liver, 1991-2017

Bisphenol A (BPA) is a widely spreading environmental endocrine disruptor . Its characteristics, including small doses and frequent contact, make it easy to enter human body through drinking water, food, air and other pathways, leading to tumors, infertility, and liver damage. The present review summarizes the underlying mechanism of oxidative stress and its related effects induced by BPA in the liver. The progress of the mechanism for oxidative stress induced by BPA is summarized, including mitochondrial dysfunction, lipid peroxidation and inflammation reaction, liver dyslipidemia, apoptosis, and cell death mechanism. In the future, it is necessary to elucidate the molecular mechanisms and timing of oxidative stress to clarify the effects on different exposures to different genders and growth stages. Besides, studying the toxic effects on BPA surrogates, BPA metabolites and BPA combined with other pollutants in the environment is beneficial to clarify the environmental and human health effects of BPA and provide technical reference for the development of practical control measures.

The Redox Theory of Development

Significance: The geological record shows that as atmospheric O2 levels increased, it concomitantly coincided with the evolution of metazoans. More complex, higher organisms contain a more cysteine-rich proteome, potentially as a means to regulate homeostatic responses in a more O2-rich environment. Regulation of redox-sensitive processes to control development is likely to be evolutionarily conserved. Recent Advances: During early embryonic development, the conceptus is exposed to varying levels of O2. Oxygen and redox-sensitive elements can be regulated to promote normal development, defined as changes to cellular mass, morphology, biochemistry, and function, suggesting that O2 is a developmental morphogen. During periods of O2 fluctuation, embryos are "reprogrammed," on the genomic and metabolic levels. Reprogramming imparts changes to particular redox couples (nodes) that would support specific post-translational modifications (PTMs), targeting the cysteine proteome to regulate protein function and development. Critical Issues: Major developmental events such as stem cell expansion, proliferation, differentiation, migration, and cell fate decisions are controlled through oxidative PTMs of cysteine-based redox nodes. As such, timely coordinated redox regulation of these events yields normal developmental outcomes and viable species reproduction. Disruption of normal redox signaling can produce adverse developmental outcomes. Future Directions: Furthering our understanding of the redox-sensitive processes/pathways, the nature of the regulatory PTMs involved in development and periods of activation/sensitivity to specific developmental pathways would greatly support the theory of redox regulation of development, and would also provide rationale and direction to more fully comprehend poor developmental outcomes, such as dysmorphogenesis, functional deficits, and preterm embryonic death.

Quantifying Activity for Repair of the DNA Lesion 8-Oxoguanine by Oxoguanine Glycosylase 1 (OGG1) in Mouse Adult and Fetal Brain Nuclear Extracts Using Biotin-Labeled DNA

The reactive oxygen species (ROS)-initiated DNA lesion 8-oxoguanine (8-oxoG) is commonly used as a biomarker to measure oxidative stress levels in tissue samples from animals and humans. This lesion also can play a pathogenic role in cancer, birth defects, and neurodegeneration, among other disorders. The level of 8-oxoG may be enhanced due to ROS-initiating environmental factors (e.g., drugs, gamma radiation, microbial infection) or due to a decrease in the activity of oxoguanine glycosylase 1 (OGG1), an enzyme that repairs this lesion. Measurement of the activity of OGG1 can be useful in elucidating mechanisms and complements measurements of 8-oxoG levels in tissues of interest. This protocol describes an assay for measuring the activity of 8-oxoG in mouse adult and fetal brain tissues. Briefly, a synthetic duplex containing the 8-oxoG residue in one of the nucleotides (49-mer), labeled with biotin at the 3'-end, is incubated with protein extract from the tissue of interest containing OGG1, which cleaves the 8-oxoG residue producing a cleavage product of ~27-mer. The percent cleavage quantifies the activity of OGG1 in that tissue. The biotin tag allows rapid and sensitive detection of the cleavage product via chemiluminescence, avoiding the problems of safety and short half-lives of radionuclides encountered in assays employing a radioactively-labeled substrate.

Oxidative stress and DNA damage in the mechanism of fetal alcohol spectrum disorders

This review covers molecular mechanisms involving oxidative stress and DNA damage that may contribute to morphological and functional developmental disorders in animal models resulting from exposure to alcohol (ethanol, EtOH) in utero or in embryo culture. Components covered include: (a) a brief overview of EtOH metabolism and embryopathic mechanisms other than oxidative stress; (b) mechanisms within the embryo and fetal brain by which EtOH increases the formation of reactive oxygen species (ROS); (c) critical embryonic/fetal antioxidative enzymes and substrates that detoxify ROS; (d) mechanisms by which ROS can alter development, including ROS-mediated signal transduction and oxidative DNA damage, the latter of which leads to pathogenic genetic (mutations) and epigenetic changes; (e) pathways of DNA repair that mitigate the pathogenic effects of DNA damage; (f) related indirect mechanisms by which EtOH enhances risk, for example by enhancing the degradation of some DNA repair proteins; and, (g) embryonic/fetal pathways like NRF2 that regulate the levels of many of the above components. Particular attention is paid to studies in which chemical and/or genetic manipulation of the above mechanisms has been shown to alter the ability of EtOH to adversely affect development. Alterations in the above components are also discussed in terms of: (a) individual embryonic and fetal determinants of risk and (b) potential risk biomarkers and mitigating strategies. FASD risk is likely increased in progeny which/who are biochemically predisposed via genetic and/or environmental mechanisms, including enhanced pathways for ROS formation and/or deficient pathways for ROS detoxification or DNA repair.

Measurement of the Oxidative DNA Lesion 8-Oxoguanine (8-oxoG) by ELISA or by High-Performance Liquid Chromatography (HPLC) with Electrochemical Detection

Reactive oxygen species (ROS) can oxidize cellular macromolecules like DNA, causing DNA damage. The most common form of DNA damage is the 8-oxoguanine (8-oxoG) lesion, typically repaired by the base excision repair (BER) pathway, which is initiated by the enzyme oxoguanine glycosylase 1 (OGG1). ROS are produced endogenously and can be enhanced by environmental factors, such as xenobiotics, radiation, and microbial pathogens. As a commonly used biomarker of oxidative damage, 8-oxoG can be measured in two different ways described herein. Commercially available ELISA kits allow for easy detection of the 8-oxoG lesion, while more difficult HPLC assays with UV and electrochemical detection allow for a more definitive identification and quantification of 8-oxoG.

Protective Effects of Quercetin Against Cadmium Chloride-Induced Oxidative Injury in Goat Sperm and Zygotes

Quercetin, a plant-derived flavonoid, is frequently used as an antioxidant for efficient anti-oxidative capacity. However, whether quercetin has protective effects on goat sperm and preimplantation embryos against Cd²⁺-induced oxidative injury is still unclear. So, we researched the influence of quercetin on goat sperm and zygotes respectively under the oxidative stress induced by Cd²⁺. In our study, quercetin decreased the malonaldehyde (MDA) and reactive oxygen species (ROS) levels caused by Cd²⁺ in goat sperm (p < 0.05), which facilitated sperm characteristics including motility, survival rates, membrane integrity, and mitochondria activity during storage in vitro and subsequent embryo development (p < 0.05). Moreover, in goat zygotes, quercetin decreased peroxidation products including ROS, MDA, and carbonyl through preserving or maintaining mitochondrial function, gene expression, and anti-oxidative products such as glutathione peroxidase, superoxide dismutase, and catalase, which ameliorated subsequent embryo development and embryo quality (p < 0.05). Taken together, these results suggest that quercetin protects both goat sperm and preimplantation embryos from Cd²⁺-induced oxidative stress.

Fetal oxidative stress mechanisms of neurodevelopmental deficits and exacerbation by ethanol and methamphetamine

In utero exposure of mouse progeny to alcohol (ethanol, EtOH) and methamphetamine (METH) causes substantial postnatal neurodevelopmental deficits. One emerging pathogenic mechanism underlying these deficits involves fetal brain production of reactive oxygen species (ROS) that alter signal transduction, and/or oxidatively damage cellular macromolecules like lipids, proteins, and DNA, the latter leading to altered gene expression, likely via non-mutagenic mechanisms. Even physiological levels of fetal ROS production can be pathogenic in biochemically predisposed progeny, and ROS formation can be enhanced by drugs like EtOH and METH, via activation/induction of ROS-producing NADPH oxidases (NOX), drug bioactivation to free radical intermediates by prostaglandin H synthases (PHS), and other mechanisms. Antioxidative enzymes, like catalase in the fetal brain, while low, provide critical protection. Oxidatively damaged DNA is normally rapidly repaired, and fetal deficiencies in several DNA repair proteins, including oxoguanine glycosylase 1 (OGG1) and breast cancer protein 1 (BRCA1), enhance the risk of drug-initiated postnatal neurodevelopmental deficits, and in some cases deficits in untreated progeny, the latter of which may be relevant to conditions like autism spectrum disorders (ASD). Risk is further regulated by fetal nuclear factor erythroid 2-related factor 2 (Nrf2), a ROS-sensing protein that upregulates an array of proteins, including antioxidative enzymes and DNA repair proteins. Imbalances between conceptal pathways for ROS formation, versus those for ROS detoxification and DNA repair, are important determinants of risk. Birth Defects Research (Part C) 108:108-130, 2016. © 2016 Wiley Periodicals, Inc.

Ketamine-induced oxidative stress at different developmental stages of zebrafish (Danio rerio) embryos

The changes induced by ketamine exposure were developmental stage-dependent, and related with the gradual development of the antioxidant defense system of the embryo, which is dependent on changes in energy-sensing pathways.

Oxidative stress, unfolded protein response, and apoptosis in developmental toxicity

Physiological development requires precise spatiotemporal regulation of cellular and molecular processes. Disruption of these key events can generate developmental toxicity in the form of teratogenesis or mortality. The mechanism behind many developmental toxicants remains unknown. While recent work has focused on the unfolded protein response (UPR), oxidative stress, and apoptosis in the pathogenesis of disease, few studies have addressed their relationship in developmental toxicity. Redox regulation, UPR, and apoptosis are essential for physiological development and can be disturbed by a variety of endogenous and exogenous toxicants to generate lethality and diverse malformations. This review examines the current knowledge of the role of oxidative stress, UPR, and apoptosis in physiological development as well as in developmental toxicity, focusing on studies and advances in vertebrates model systems.

Oxidative DNA damage in the in utero initiation of postnatal neurodevelopmental deficits by normal fetal and ethanol-enhanced oxidative stress in oxoguanine glycosylase 1 knockout mice

Studies in mice with deficient antioxidative enzymes have shown that physiological levels of reactive oxygen species (ROS) can adversely affect the developing embryo and fetus. Herein, DNA repair-deficient progeny of oxoguanine glycosylase 1 (ogg1)-knockout mice lacking repair of the oxidative DNA lesion 8-oxo-2'-deoxyguanosine (8-oxodGuo) exhibited enhanced postnatal neurodevelopmental deficits, revealing the pathogenic potential of 8-oxodGuo initiated by physiological ROS production in fetal brain and providing the first evidence of a pathological phenotype for ogg1-knockout mice. Moreover, when exposed in utero to ethanol (EtOH), ogg1-knockout progeny exhibited higher levels of 8-oxodGuo in fetal brain and more severe postnatal neurodevelopmental deficits than wild-type littermates, both of which were blocked by pretreatment with the free radical trapping agent phenylbutylnitrone. These results suggest that ROS-initiated DNA oxidation, as distinct from altered signal transduction, contributes to neurodevelopmental deficits caused by in utero EtOH exposure, and fetal DNA repair is a determinant of risk.

Pro-oxidant/antioxidant balance controls pancreatic β-cell differentiation through the ERK1/2 pathway

During embryogenesis, the intrauterine milieu affects cell proliferation, differentiation, and function by modifying gene expression in susceptible cells, such as the pancreatic β-cells. In this limited energy environment, mitochondrial dysfunction can lead to overproduction of reactive oxygen species (ROS) and to a decline in β-cell function. In opposition to this toxicity, ROS are also required for insulin secretion. Here we investigated the role of ROS in β-cell development. Surprisingly, decreasing ROS production in vivo reduced β-cell differentiation. Moreover, in cultures of pancreatic explants, progenitors were highly sensitive to ROS stimulation and responded by generating β-cells. ROS enhanced β-cell differentiation through modulation of ERK1/2 signaling. Gene transfer and pharmacological manipulations, which diminish cellular ROS levels, also interfered with normal β-cell differentiation. This study highlights the role of the redox balance on β-cell development and provides information that will be useful for improving β-cell production from embryonic stem cells, a step in cell therapy for diabetes.

Protective effect of quercetin on the development of preimplantation mouse embryos against hydrogen peroxide-induced oxidative injury

Quercetin, a plant-derived flavonoid in Chinese herbs, fruits and wine, displays antioxidant properties in many pathological processes associated with oxidative stress. However, the effect of quercetin on the development of preimplantation embryos under oxidative stress is unclear. The present study sought to determine the protective effect and underlying mechanism of action of quercetin against hydrogen peroxide (H₂O₂)-induced oxidative injury in mouse zygotes. H₂O₂ treatment impaired the development of mouse zygotes in vitro, decreasing the rates of blastocyst formation and hatched, and increasing the fragmentation, apoptosis and retardation in blastocysts. Quercetin strongly protected zygotes from H₂O₂-induced oxidative injury by decreasing the reactive oxygen species level, maintaining mitochondrial function and modulating total antioxidant capability, the activity of the enzymatic antioxidants, including glutathione peroxidase and catalase activity to keep the cellular redox environment. Additionally, quercetin had no effect on the level of glutathione, the main non-enzymatic antioxidant in embryos.

Developmental role of nuclear factor E2-related factor 2 in mitigating methamphetamine fetal toxicity and postnatal neurodevelopmental deficits

Nuclear factor E2-related factor 2 (Nrf2) is a transcription factor that mediates protective responses to oxidative stress, but its developmental role is unknown. Herein, we treated pregnant Nrf2-deficient knockout mice with methamphetamine (METH) (5-40 mg/kg ip), which increases fetal reactive oxygen species (ROS) and oxidatively damaged DNA in fetal brain tissue. METH-exposed Nrf2(-/-) fetuses were unable to increase mRNA levels of ROS-protective heme oxygenase-1, NAD(P)H:quinone oxidoreductase, or oxoguanine glycosylase 1, unlike wild-type controls, and exhibited enhanced DNA oxidation, fetal resorption, edema, and reduced fetal weight, with greater toxicity in female Nrf2(-/-) fetuses. Postnatal neurodevelopmental deficits in activity and olfactory function were exacerbated, with gender-dependent differences, and the olfactory bulb GABAergic marker GAD-65 was decreased in Nrf2(-/-) offspring exposed in utero to METH. In utero METH-initiated olfactory deficits may be a sensitive postnatal functional test for long-term neurotoxicity, and indicated a broad fetal role for Nrf2. The results show that fetal Nrf2 deficiency enhances METH-initiated oxidative DNA damage and toxicity, suggesting that Nrf2 activation of cytoprotective proteins mitigates the effects of ROS and their oxidative damage to cellular macromolecules, thereby protecting the developing fetus from adverse structural and postnatal neurodevelopmental consequences.

Short-term effects of neuroactive pharmaceutical drugs on a fish species: biochemical and behavioural effects

The presence of pharmaceutical residues in the aquatic environment is receiving great attention since significant levels of contamination have been found, not only in sewage treatment plant effluents, but also in open waters. In our study, the toxicity of three anticonvulsant drugs commonly found in the environment (diazepam, carbamazepine, and phenytoin) was evaluated in Lepomis gibbosus (pumpkinseed sunfish). This study focused on oxidative stress parameters, namely: glutathione reductase (GRed), glutathione S-transferases (GSTs), catalase (CAT), and lipid peroxidation (thiobarbituric acid reactive substances, TBARS) in the hepatic, digestive, and gill tissues of exposed animals. Simultaneously, we assessed the effects of these drugs in terms of behavioural parameters, such as scototaxis and activity. Exposure to diazepam caused an increase in GST activities in the gills and an inhibition of GRed in the digestive tract, relative to control, suggesting an antioxidant response. It also caused fish to spend more time swimming and less time in a refuge area (black compartment of an aquarium). Exposure to carbamazepine caused an increase in GSTs and GRed activity in the digestive tract, which is not always consistent with the literature. A significant positive correlation was found between carbamazepine concentration and time spent in motion and a negative correlation with time spent in black compartment. Exposure to phenytoin was responsible for adaptive responses in the activities of CAT and GSTs (in the liver), but it did not elicit any behavioural alterations. Although all three drugs seemed to induce oxidative stress in some organs, peroxidative damage (measured as TBARS concentrations) was not found at the selected range of concentrations. Our results enlighten the need for more research on the ecological consequences of pharmaceuticals in the aquatic environment, especially drugs that interfere with the CNS and behaviour, because the net outcome of these effects may be difficult to predict.

A role for glutathione, independent of oxidative stress, in the developmental toxicity of methanol

Oxidative stress and reactive oxygen species (ROS) have been implicated in the teratogenicity of methanol (MeOH) in rodents, both in vivo and in embryo culture. We explored the ROS hypothesis further in vivo in pregnant C57BL/6J mice. Following maternal treatment with a teratogenic dose of MeOH, 4 g/kg via intraperitoneal (ip) injection on gestational day (GD) 12, there was no increase 6h later in embryonic ROS formation, measured by 2',7'-dichlorodihydrofluorescin diacetate (DCFH-DA) fluorescence, despite an increase observed with the positive control ethanol (EtOH), nor was there an increase in embryonic oxidatively damaged DNA, quantified as 8-oxo-2'-deoxyguanosine (8-oxodG) formation. MeOH teratogenicity (primarily ophthalmic anomalies, cleft palate) also was not altered by pre- and post-treatment with varying doses of the free radical spin trapping agent alpha-phenyl-N-tert-butylnitrone (PBN). In contrast, pretreatment with L-buthionine-(S,R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, depleted maternal hepatic and embryonic GSH, and enhanced some new anomalies (micrognathia, agnathia, short snout, fused digits, cleft lip, low set ears), but not the most common teratogenic effects of MeOH (ophthalmic anomalies, cleft palate) in this strain. These results suggest that ROS did not contribute to the teratogenic effects of MeOH in this in vivo mouse model, in contrast to results in embryo culture from our laboratory, and that the protective effect of GSH in this model may arise from its role as a cofactor for formaldehyde dehydrogenase in the detoxification of formaldehyde.

The free radical spin trapping agent phenylbutylnitrone reduces fetal brain DNA oxidation and postnatal cognitive deficits caused by in utero exposure to a non-structurally teratogenic dose of ethanol: a role for oxidative stress

Reactive oxygen species (ROS), although implicated in morphological birth defects caused by ethanol (EtOH) during pregnancy, have not been directly linked to its behavioral deficits. To determine this, a pathogenic oxidative DNA lesion was measured in fetal brain, and a passive avoidance learning test was assessed postnatally in the progeny of CD-1 mice treated once on gestational day 17 with 4g/kg EtOH or its saline vehicle, with or without pretreatment with the free radical spin trapping agent α-phenyl-N-tert-butylnitrone (PBN; 40mg/kg). EtOH-exposed CD-1 progeny, unlike C57BL/6 progeny, had no morphological birth defects, but exhibited a learning deficit at 12 weeks of age (p<0.001), which continued to 16 weeks in males (p<0.01). Peak blood EtOH concentrations were 2.5-fold higher in C57BL/6 mice compared to CD-1 mice given the same dose. PBN pretreatment of CD-1 dams blocked both EtOH-initiated DNA oxidation in fetal brain (p<0.05) and postnatal learning deficits (p<0.01), providing the first direct evidence for ROS in the mechanism of EtOH-initiated neurodevelopmental deficits.