Catalase Mediates Acetaldehyde Formation from Ethanol in Fetal and Neonatal Rat Brain

Embryonic alcohol exposure disrupts the ubiquitin-proteasome system

Ethanol (EtOH) is a commonly encountered teratogen that can disrupt organ development and lead to fetal alcohol spectrum disorders (FASDs); many mechanisms of developmental toxicity are unknown. Here, we used transcriptomic analysis in an established zebrafish model of embryonic alcohol exposure (EAE) to identify the ubiquitin-proteasome system (UPS) as a critical target of EtOH during development. Surprisingly, EAE alters 20S, 19S, and 11S proteasome gene expression and increases ubiquitylated protein load. EtOH and its metabolite acetaldehyde decrease proteasomal peptidase activity in a cell type-specific manner. Proteasome 20S subunit β 1 (psmb1hi2939Tg) and proteasome 26S subunit, ATPase 6 (psmc6hi3593Tg), genetic KOs define the developmental impact of decreased proteasome function. Importantly, loss of psmb1 or psmc6 results in widespread developmental abnormalities resembling EAE phenotypes, including growth restriction, abnormal craniofacial structure, neurodevelopmental defects, and failed hepatopancreas maturation. Furthermore, pharmacologic inhibition of chymotrypsin-like proteasome activity potentiates the teratogenic effects of EAE on craniofacial structure, the nervous system, and the endoderm. Our studies identify the proteasome as a target of EtOH exposure and signify that UPS disruptions contribute to craniofacial, neurological, and endodermal phenotypes in FASDs.

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.

Novel insights into alcoholic liver disease: Iron overload, iron sensing and hemolysis

The liver is the major target organ of continued alcohol consumption at risk and resulting alcoholic liver disease (ALD) is the most common liver disease worldwide. The underlying molecular mechanisms are still poorly understood despite decades of scientific effort limiting our abilities to identify those individuals who are at risk to develop the disease, to develop appropriate screening strategies and, in addition, to develop targeted therapeutic approaches. ALD is predestined for the newly evolving translational medicine, as conventional clinical and health care structures seem to be constrained to fully appreciate this disease. This concept paper aims at summarizing the 15 years translational experience at the Center of Alcohol Research in Heidelberg, namely based on the long-term prospective and detailed characterization of heavy drinkers with mortality data. In addition, novel experimental findings will be presented. A special focus will be the long-known hepatic iron accumulation, the somewhat overlooked role of the hematopoietic system and novel insights into iron sensing and the role of hepcidin. Our preliminary work indicates that enhanced red blood cell (RBC) turnover is critical for survival in ALD patients. RBC turnover is not primarily due to vitamin deficiency but rather to ethanol toxicity directly targeted to erythrocytes but also to the bone marrow stem cell compartment. These novel insights also help to explain long-known aspects of ALD such as mean corpuscular volume of erythrocytes (MCV) and elevated aspartate transaminase (GOT/AST) levels. This work also aims at identifying future projects, naming unresolved observations, and presenting novel hypothetical concepts still requiring future validation.

A study of effect of Centella asiatica on oxidative markers in the hippocampus of offsprings born to alcohol-fed pregnant rats and the correlation with their cognitive functions

OBJECTIVES

Alcohol consumption causes several harmful effects on the organs, which is hugely understated. Many deformities occur in the fetus when pregnant mothers indulge in alcoholism. Alcohol is a known teratogen, hence organ formation, particularly development of parts brain critical for cognitive function may be affected. The oxidative brain damage also could contribute to reduced cognitive efficiency of brain exposed to alcohol. In this study, effect of Centella asiatica in relieving the oxidative brain damage in offspring of alcohol fed mother rats was evaluated.

METHODS

In this study we fed alcohol (5 g/kg body weight, 30% w/v) to a group of pregnant Wistar rats during gestation period, and another group served as control. Four groups of rats (n = 6 each) were selected from the offspring of these mother rats. The groups were, control, positive (treated) control, untreated and treated from alcohol-fed mother. Their cognitive parameters were tested in water maze, shuttle box and compared. Further their oxidative status was evaluated by estimating malondialdehyde (MDA), protein carbonyl, total antioxidants and glutathione reductase (GSH) in hippocampus.

RESULTS

The results suggested that there was significantly high cognitive performance in maze test and shuttle box memory retention in rats treated with C. asiatica water extract and the antioxidant levels were high in their hippocampus.

CONCLUSIONS

The outcome of the study suggested that C. asiatica produced beneficial effects in reversing the alcohol induced brain damage in pregnancy.

Postnatal Antioxidant and Anti-inflammatory Treatments Prevent Early Ketamine-Induced Cortical Dysfunctions in Adult Mice

Early brain insult, interfering with its maturation, may result in psychotic-like disturbances in adult life. Redox dysfunctions and neuroinflammation contribute to long-term psychiatric consequences due to neurodevelopmental abnormalities. Here, we investigated the effects of early pharmacological modulation of the redox and inflammatory states, through celastrol, and indomethacin administration, on reactive oxygen species (ROS) amount, levels of malondialdehyde (MDA) and antioxidant enzymes (superoxide dismutase 1, SOD1, glutathione, GSH, and catalase, CAT), as well as of pro-inflammatory cytokines (tumor necrosis factor-alpha, TNF-α, interleukin-6, IL-6, and interleukin-1 beta, IL-1β), in the prefrontal cortex of adult mice exposed to a neurotoxic insult, i.e. ketamine administration, in postnatal life. Early celastrol or indomethacin prevented ketamine-induced elevations in cortical ROS production. MDA levels in ketamine-treated mice, also administered with celastrol, were comparable with the control ones. Indomethacin also prevented the increase in lipid peroxidation following early ketamine administration. Whereas no significant differences were detected in SOD1, GSH, and CAT levels between ketamine and saline-administered mice, celastrol elevated the cortical amount of these antioxidant enzymes and the same effect was induced by indomethacin per se. Both celastrol and indomethacin prevented ketamine-induced enhancement in TNF-α and IL-1β levels, however, they had no effects on increased IL-6 amount resulting from ketamine exposure in postnatal life. In conclusion, our data suggest that an early increase in cortical ROS scavenging and reduction of lipid peroxidation, via the enhancement of antioxidant defense, together with inhibition of neuroinflammation, may represent a therapeutic opportunity against psychotic-like disturbances resulting, later in life, from the effects of a neurotoxic insult on the developing brain.

Learning experiences comprising central ethanol exposure in rat neonates: Impact upon respiratory plasticity and the activity of brain catalase

Fetal ethanol exposure represents a risk factor for sudden infant death syndrome, and the respiratory effects of fetal ethanol exposure promote hypoxic ischemic consequences. This study analyzes central ethanol's effects upon breathing plasticity during an ontogenetic stage equivalent to the human third gestational trimester. Ethanol's unconditioned breathing effects and their intervention in learning processes were examined. Since central ethanol is primarily metabolized via the catalase system, we also examined the effects of early history with the drug upon this system. During postnatal days 3, 5, and 7 (PDs 3-7), pups were intracisternally administered with vehicle or ethanol (300 mg%). They were tested in a plethysmograph scented or not scented with ethanol odor. The state of intoxication attenuated the onset of apneas, a phenomenon that is suggestive of ethanol's anxiolytic effects given the state of arousal caused by the novel environment and the stress of ethanol administration. At PD9, pups were evaluated when sober under sequential air conditions (initial-normoxia, hypoxia, and recovery-normoxia), with or without the presence of ethanol odor. Initial apneic episodes increased when ethanol intoxication was previously associated with the odor. Pups then ingested ethanol, and brain catalase activity was determined. Pre-exposure to ethanol intoxication paired with the odor of the drug resulted in heightened enzymatic activity. Central ethanol exposure appears to exert antianxiety effects that attenuate apneic disruptions. However, during withdrawal, the cues associated with such effects elicit an opposite reaction. The activity of the catalase system was also dependent upon learning processes that involved the association of environmental stimuli and ethanol intoxication.

Yin and Yang of mitochondrial ROS in Drosophila

In this study, we test the hypothesis that Drosophila larvae producing mildly elevated levels of endogenous mitochondrial reactive oxygen species (ROS) benefit in stressful environmental conditions due to the priming of antioxidant responses. Reactive oxygen species (ROS) are produced as a by-product of oxidative phosphorylation and may be elevated when mutations decrease the efficiency of ATP production. In moderation, ROS are necessary for cell signaling and organismal health, but in excess can damage DNA, proteins, and lipids. We utilize two Drosophila melanogaster strains (Dahomey and Alstonville) that share the same nuclear genetic background but differ in their mitochondrial DNA haplotypes. Previously, we reported that Dahomey larvae harboring the V161L ND4 mtDNA mutation have reduced proton pumping and higher levels of mitochondrial ROS than Alstonville larvae when they are fed a 1:2 protein: carbohydrate (P:C) diet. Here, we explore the potential for mitochondrial ROS to provide resistance to dietary stressors by feeding larvae 1:2 P:C food supplemented with ethanol or hydrogen peroxide (H₂O₂). When fed a diet supplemented with ethanol or H₂O₂, Dahomey develop more quickly than Alstonville into larger pupae, while Alstonville developed faster on the control. Dahomey larvae displayed higher antioxidant capacity than Alstonville on all diets, with mitochondrial H₂O₂ levels unchanged after the addition of stressors. Addition of stressors to the diet did not affect the mitochondrial functions of Dahomey larvae as measured by mitochondrial membrane potential, respiratory control ratio, or larval survival after bacterial challenge. In contrast, Alstonville larvae developed slower, had lower pupal weight, higher cytosolic H₂O₂, and had reduced mitochondrial functions. Further, Alstonville larvae fed the ethanol treated diet had lower survival after bacterial infection than those fed the control diet. Surprisingly, they had greater survival when fed diet with H₂O₂ indicating a mitotype by stressor interaction that influences the immune response. Overall, these data suggest that elevated mitochondrial ROS in Dahomey can result in greater antioxidant capacity that prevents oxidative damage from exogenous stressors and may be a conserved response to high ethanol found in rotting fruit.

Prenatal Alcohol Exposure as a Case of Involuntary Early Onset of Alcohol Use: Consequences and Proposed Mechanisms From Animal Studies

Prenatal alcohol exposure has been found to be an important factor determining later consumption of this drug. In humans, despite the considerable diversity of variables that might influence alcohol consumption, longitudinal studies show that maternal alcohol intake during gestation is one of the best predictors of later alcohol use from adolescence to young adulthood. Experimental studies with animals also provide abundant evidence of the effects of prenatal alcohol exposure on later alcohol intake. In addition to increased consumption, other effects include enhanced palatability and attractiveness of alcohol flavor as well as sensitization to its sensory and reinforcing effects. Most of these outcomes have been obtained after exposing rats to binge-like administrations of moderate alcohol doses during the last gestational period when the fetus is already capable of detecting flavors in the amniotic fluid and learning associations with aversive or appetitive consequences. On this basis, it has been proposed that one of the mechanisms underlying the increased acceptance of alcohol after its prenatal exposure is the acquisition (by the fetus) of appetitive learning via an association between the sensory properties of alcohol and its reinforcing pharmacological effects. It also appears that this prenatal appetitive learning is mediated by the activation of the opioid system, with fetal brain acetaldehyde playing an important role, possibly as the main chemical responsible for its activation. Here, we review and analyze together the results of all animal studies testing these hypotheses through experimental manipulation of the behavioral and neurochemical elements of the assumed prenatal association. Understanding the mechanisms by which prenatal alcohol exposure favors the early initiation of alcohol consumption, along with its role in the causal pathway to alcohol disorders, may allow us to find strategies to mitigate the behavioral effects of this early experience with the drug. We propose that prenatal alcohol exposure is regarded as a case of involuntary early onset of alcohol use when designing prevention policies. This is particularly important, given the notion that the sooner alcohol intake begins, the greater the possibility of a continued history of alcohol consumption that may lead to the development of alcohol use disorders.

Effects of Acute Ethanol Administration on Brain Oxidative Status: The Role of Acetaldehyde

BACKGROUND

Ethanol (EtOH), one of the most widely consumed substances of abuse, can induce brain damage and neurodegeneration. EtOH is centrally metabolized into acetaldehyde, which has been shown to be responsible for some of the neurophysiological and cellular effects of EtOH. Although some of the consequences of chronic EtOH administration on cell oxidative status have been described, the mechanisms by which acute EtOH administration affects the brain's cellular oxidative status and the role of acetaldehyde remain to be elucidated in detail.

METHODS

Swiss CD-I mice were pretreated with the acetaldehyde-sequestering agent d-penicillamine (DP; 75 mg/kg, i.p.) or the antioxidant lipoic acid (LA; 50 mg/kg, i.p.) 30 minutes before EtOH (2.5 g/kg, i.p.) administration. Animals were sacrificed 30 minutes after EtOH injection. Glutathione peroxidase (GPx) mRNA levels; GPx and glutathione reductase (GR) enzymatic activities; reduced glutathione (GSH), glutathione disulfide (GSSG), glutamate, g-L-glutamyl-L-cysteine (Glut-Cys), and malondialdehyde (MDA) concentrations; and protein carbonyl group (CG) content were determined in whole-brain samples.

RESULTS

Acute EtOH administration enhanced GPx activity and the GSH/GSSG ratio, while it decreased GR activity and GSSG concentration. Pretreatment with DP or LA only prevented GPx activity changes induced by EtOH.

CONCLUSIONS

Altogether, these results show the capacity of a single dose of EtOH to unbalance cellular oxidative homeostasis.

Ethanol-induced DNA repair in neural stem cells is transforming growth factor β1-dependent

Following neurotoxic damage, cells repair their DNA, and survive or undergo apoptosis. This study tests the hypothesis that ethanol induces a DNA damage response (DDR) in neural stem cells (NSCs) that promotes excision repair (ER) and this repair is influenced by the growth factor environment. Non-immortalized NSCs treated with fibroblast growth factor 2 or transforming growth factor (TGF) β1 were exposed to ethanol. Ethanol increased total DNA damage, reactive oxygen species, and oxidized DNA bases. TGFβ1 potentiated these toxic effects. Transcriptional analyses of cultured NSCs revealed ethanol-induced increases in transcripts related to the DDR (e.g., Hus1 and p53), base ER (e.g., Mutyh and Nthl1), and nucleotide ER (e.g., Xpc), particularly in the presence of TGFβ1. Expression and activity of ER proteins were affected by ethanol. Similar changes occurred in proliferating cells of ethanol-treated mouse fetuses. Ethanol-induced DNA repair in NSCs depends on the ambient growth factors. Gene products for DNA repair in stem cells are among the first biomarkers identifying fetal alcohol-induced damage.

Is catalase involved in the effects of systemic and pVTA administration of 4-methylpyrazole on ethanol self-administration?

The oxidative metabolism of ethanol into acetaldehyde involves several enzymes, including alcohol dehydrogenase (ADH) and catalase-hydrogen peroxide (H₂O₂). In this regard, while it is well known that 4-methylpyrazole (4-MP) acts by inhibiting ADH in the liver, little attention has been placed on its ability to interfere with fatty acid oxidation-mediated generation of H₂O₂, a mechanism that may indirectly affect catalase whose enzymatic activity requires H₂O₂. The aim of our investigation was twofold: 1) to evaluate the effect of systemic (i.p. [intraperitoneal]) and local (into the posterior ventral tegmental area, pVTA) administration of 4-MP on oral ethanol self-administration, and 2) to assess ex vivo whether or not systemic 4-MP affects liver and brain H₂O₂ availability. The results show that systemic 4-MP reduced ethanol but not acetaldehyde or saccharin self-administration, and decreased the ethanol deprivation effect. Moreover, local intra-pVTA administration of 4-MP reduced ethanol but not saccharin self-administration. In addition, although unable to affect basal catalase activity, systemic administration of 4-MP decreased H₂O₂ availability both in liver and in brain. Overall, these results indicate that 4-MP interferes with ethanol self-administration and suggest that its behavioral effects could be due to a decline in catalase-H₂O₂ system activity as a result of a reduction of H₂O₂ availability, thus highlighting the role of central catalase-mediated metabolism of ethanol and further supporting the key role of acetaldehyde in the reinforcing properties of ethanol.

Brain Acetaldehyde Exposure Impacts upon Neonatal Respiratory Plasticity and Ethanol-Related Learning in Rodents

Prior studies indicate that neonates are very sensitive to ethanol's positive reinforcing effects and to its depressant effects upon breathing. Acetaldehyde (ACD) appears to play a major role in terms of modulating early reinforcing effects of the drug. Yet, there is no pre-existing literature relative to the incidence of this metabolite upon respiratory plasticity. The present study analyzed physiological and behavioral effects of early central administrations of ethanol, acetaldehyde or vehicle. Respiration rates (breaths/min) were registered at post-natal days (PDs) 2 and 4 (post-administration time: 5, 60, or 120 min). At PD5, all pups were placed in a context (plethysmograph) where they had previously experienced the effects of central administrations and breathing patterns were recorded. Following this test, pups were evaluated using and operant conditioning procedure where ethanol or saccharin served as positive reinforcers. Body temperatures were also registered prior to drug administrations as well as at the beginning and the end of each specific evaluation. Across days, breathing responses were high at the beginning of the evaluation session and progressively declined as a function of the passage of time. At PDs 2 and 4, shortly after central administration (5 min), ACD exerted a significant depression upon respiration frequencies. At PD5, non-intoxicated pups with a prior history of ACD central administrations, exhibited a marked increase in respiratory frequencies; a result that probably indicates a conditioned compensatory response. When operant testing procedures were conducted, prior ethanol or ACD central administrations were found to reduce the reinforcing effects of ethanol. This was not the case when saccharin was employed as a reinforcer. As a whole, the results indicate a significant role of central ACD upon respiratory plasticity of the neonate and upon ethanol's reinforcing effects; phenomena that affect the physiological integrity of the immature organism and its subsequent affinity for ethanol operationalized through self-administration procedures.

Alcohol Teratogenesis: Mechanisms of Damage and Strategies for Intervention

There are multiple mechanisms by which alcohol can damage the developing brain, but the type of damage induced will depend on the amount and developmental timing of exposure, along with other maternal and genetic factors. This article reviews current perspectives on how ethanol can produce neuroteratogenic effects by its interactions with molecular regulators of brain development. The current evidence suggests that alcohol produces many of its damaging effects by exerting specific actions on molecules that regulate key developmental processes (e.g., L1 cell adhesion molecule, alcohol dehydrogenase, catalase), interfering with the early development of midline serotonergic neurons and disrupting their regulatory-signaling function for other target brain structures, interfering with trophic factors that regulate neurogenesis and cell survival, or inducing excessive cell death via oxidative stress or activation of caspase-3 proteases. The current understanding of pathogenesis mechanisms suggests several strategic approaches to develop rational molecular prevention. However, the development of behavioral and biologic treatments for alcohol-affected children is crucial because it is unlikely that effective delivery of preventative interventions can realistically be achieved in ways to prevent prenatal damage in at-risk pregnancies. Toward that end, behavioral training that promotes experience-dependent neuroplasticity has been effective in a rat model of cerebellar damage induced by alcohol exposure during the period of brain development that is comparable to that of the human third trimester.

Maternal Alcohol Consumption during Pregnancy and Early Age Leukemia Risk in Brazil

Objectives. To investigate the association between the maternal alcohol consumption during pregnancy and early age leukemia (EAL) in offspring. Methods. Datasets were analyzed from a case-control study carried out in Brazil during 1999-2007. Data were obtained by maternal interviews using a standardized questionnaire. The present study included 675 children (193 acute lymphoid leukemia (ALL), 59 acute myeloid leukemia (AML), and 423 controls). Unconditional logistic regression was performed, and adjusted odds ratios (adj. OR) on the association between alcohol consumption and EAL were ascertained. Results. Alcohol consumption was reported by 43% of ALL and 39% of AML case mothers and 35.5% of controls'. Beer consumption before and during pregnancy was associated with ALL in crude analysis (OR = 1.54, 95% CI, 1.08-2.19), although in adjusted analysis no statistical significance was found. For weekly intake of ≤1 glass (adj. OR = 1.30, 95% CI, 0.71-2.36) and ≥1 glass/week (adj. OR = 1.47, 95% CI, 0.88-2.46) a potential dose-response was observed (P trend < 0.03). Conclusion. This study failed to support the hypothesis of an increased risk of EAL associated with maternal alcohol intake during pregnancy, neither with the interaction with tobacco nor with alcohol consumption.

Acetaldehyde, not ethanol, impairs myelin formation and viability in primary mouse oligodendrocytes

BACKGROUND

Excessive ethanol (EtOH) drinking is associated with white matter loss in the brain at all stages of life. Myelin-forming oligodendrocytes (OLs) are a major component of white matter, but their involvement in EtOH-mediated white matter loss is unclear. Myelination continues throughout the life with highest rates during fetal development and adolescence. However, little is known about the effects of EtOH and its principal metabolite acetaldehyde (ACD) on OLs at the cellular level.

METHODS

We compared the responses to different concentrations of EtOH or ACD by primary OLs in culture.

RESULTS

EtOH did not cause significant cell death at concentrations lower than 120 mM, even after 24 hours. In comparison, ACD was highly lethal at doses above 50 μM. High concentrations of EtOH (120 mM) and ACD (500 μM) for 24 hours did not reduce myelin in mature OLs. Myelin production and OL differentiation were significantly impaired by 7 days exposure to 500 or 50 μM ACD but not 120 mM EtOH.

CONCLUSIONS

This study shows that OLs are relatively resistant to EtOH, even at a concentration more than 4 times the typical blood EtOH concentrations associated with social drinking (10 to 30 mM). In contrast, OLs are much more sensitive to ACD than EtOH, particularly with long-term exposure. This suggests that part of white matter loss in response to EtOH, especially during high rates of myelin formation, may be due in part to the effects of its principal metabolite ACD.

Effect of boric acid on oxidative stress in rats with fetal alcohol syndrome

To the best of our knowledge, this is the first study concerning the effect of boric acid (BA) administration on fetal alcohol syndrome (FAS). In this study, the aim was to investigate prenatal alcohol-induced oxidative stress on the cerebral cortex of newborn rat pups and assess the protective and beneficial effects of BA supplementation on rats with FAS. Pregnant rats were divided into three groups, namely the control, alcohol and alcohol + boric acid groups. As markers of alcohol-induced oxidative stress in the cerebral cortex of the newborn pups, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) levels were measured. Although the MDA levels in the alcohol group were significantly increased compared with those in the control group (P<0.05), the MDA level in the alcohol + boric acid group was shown to be significantly decreased compared with that in the alcohol group (P<0.01). The CAT activity of the alcohol + boric acid group was significantly higher than that in the alcohol group (P<0.05). The GPx activity in the alcohol group was decreased compared with that in the control group (P<0.05). These results demonstrate that alcohol is capable of triggering damage to membranes of the cerebral cortex of rat pups and BA could be influential in antioxidant mechanisms against oxidative stress resulting from prenatal alcohol exposure.

Comparison of minipig, dog, monkey and human drug metabolism and disposition

INTRODUCTION

This article gives an overview of the drug metabolism and disposition (ADME) characteristics of the most common non-rodent species used in toxicity testing of drugs (minipigs, dogs, and monkeys) and compares these to human characteristics with regard to enzymes mediating the metabolism of drugs and the transport proteins which contribute to the absorption, distribution and excretion of drugs.

METHODS

Literature on ADME and regulatory guidelines of relevance in drug development of small molecules has been gathered.

RESULTS

Non-human primates (monkeys) are the species that is closest to humans in terms of genetic homology. Dogs have an advantage due to the ready availability of comprehensive background data for toxicological safety assessment and dogs are easy to handle. Pigs have been used less than dogs and monkeys as a model in safety assessment of drug candidates. However, when a drug candidate is metabolised by aldehyde oxidase (AOX1), N-acetyltransferases (NAT1 and NAT2) or cytochrome (CYP2C9-like) enzymes which are not expressed in dogs, but are present in pigs, this species may be a better choice than dogs, provided that adequate exposure can be obtained in pigs. Conversely, pigs might not be the right choice if sulfation, involving 3-phospho-adenosyl-5-phosphosulphate sulphotransferase (PAPS) is an important pathway in the human metabolism of a drug candidate.

DISCUSSION

In general, the species selection should be based on comparison between in vitro studies with human cell-based systems and animal-cell-based systems. Results from pharmacokinetic studies are also important for decision-making by establishing the obtainable exposure level in the species. Access to genetically humanized mouse models and highly sensitive analytical methods (accelerator mass spectrometry) makes it possible to improve the chance of finding all metabolites relevant for humans before clinical trials have been initiated and, if necessary, to include another animal species before long term toxicity studies are initiated. In conclusion, safety testing can be optimized by applying knowledge about species ADME differences and utilising advanced analytical techniques.

Ethanol pharmacokinetics in neonates and infants

Introduction

Ethanol has been used for years in neonatal and infant liquid medications, yet the pharmacokinetics, pharmacodynamics, and safety of ethanol in this vulnerable population have not been well characterized. The purpose of this review is to raise awareness of ethanol use as an excipient in neonatal and infant medications and to provide insight, based on the available evidence, into clearance rates of ethanol in babies. We also discuss ethanol pharmacokinetics in adults, theoretical pharmacokinetic changes in neonates and infants as it may apply to ethanol disposition, and case reports involving ethanol exposure in neonates and infants.

Materials and methods

This study was a narrative review in which relevant papers were selected using databases and scientific search engines such as PubMed with the key words ethanol, infant, and newborninfant.

Results

It remains unclear what ethanol exposure is safe for neonates and infants. The Food and Drug Administration and American Academy of Pediatrics have both taken action, by either setting limits of ethanol content in over-the-counter medications or by recommending restricted exposure to ethanol-containing pediatric formulations.

Conclusions

Until the short- and long-term health effects of chronic ethanol administration can be further characterized, ethanol-containing medications should be used with caution.

Induction of brain cytochrome P450 2E1 boosts the locomotor-stimulating effects of ethanol in mice

In the central nervous system ethanol (EtOH) is metabolized into acetaldehyde by different enzymes. Brain catalase accounts for 60% of the total production of EtOH-derived acetaldehyde, whereas cerebral cytochrome P450 2E1 (CYP 2E1) produces 20% of this metabolite. Acetaldehyde formed by the activity of central catalase has been implicated in some of the neurobehavioral properties of EtOH, yet the contribution of CYP 2E1 to the pharmacological actions of this drug has not been investigated. Here we assessed the possible participation of CYP 2E1 in the behavioral effects of EtOH. Thus, we induced CYP 2E1 activity and expression by exposing mice to chronic acetone intake (1% v/v for 10 days) and examined its consequences on the stimulating and uncoordinating effects of EtOH (0-3.2 g/kg) injected intraperitoneally. Our data showed that 24 h after withdrawal of acetone brain expression and activity of CYP 2E1 was induced. Furthermore, the locomotion produced by EtOH was boosted over the same interval of time. Locomotor stimulation produced by amphetamine or tert-butanol was unchanged by previous treatment with acetone. EtOH-induced motor impairment as evaluated in a Rota-Rod apparatus was unaffected by the preceding exposure to acetone. These results indicate that cerebral CYP 2E1 activity could contribute to the locomotor-stimulating effects of EtOH, and therefore we suggest that centrally produced acetaldehyde might be a possible mediator of some EtOH-induced pharmacological effects.

Modulation of ethanol-induced conditioned place preference in mice by 3-amino-1,2,4-triazole and D-penicillamine depends on ethanol dose and number of conditioning trials

Previous studies have shown that both 3-amino-1,2,4-triazole (AT), which inhibits metabolism of ethanol (EtOH) to acetaldehyde by inhibiting catalase, and D-penicillamine (D-P), an acetaldehyde-sequestering agent, modulate EtOH-conditioned place preference (CPP) in male albino Swiss (IOPS Orl) mice. These studies followed a reference-dose-like procedure, which involves comparing cues that have both been paired with EtOH. However, the role of EtOH-derived acetaldehyde has not been examined using a standard CPP method, and efficacy of these treatments could be different under the two circumstances. In the present investigation, we manipulated the strength of CPP across five separate studies and evaluated the effect of D-P and AT on EtOH-induced CPP following a standard unbiased CPP procedure. Mice received pairings with vehicle-saline injections with one cue and, alternatively, with AT- and D-P-EtOH with another cue. Our studies indicate that AT and D-P only disrupt CPP induced by EtOH in mice when the number of conditioning sessions and the dose of EtOH are low. These findings suggest that acquisition of EtOH-induced CPP may depend on the levels of acetaldehyde available during memory acquisition and the strength of the memory. Therefore, we propose that, at least when the memory processes are labile, brain acetaldehyde could participate in the formation of Pavlovian learning elicited by EtOH.

Oxidation of ethanol in the rat brain and effects associated with chronic ethanol exposure

It has been reported that chronic and acute alcohol exposure decreases cerebral glucose metabolism and increases acetate oxidation. However, it remains unknown how much ethanol the living brain can oxidize directly and whether such a process would be affected by alcohol exposure. The questions have implications for reward, oxidative damage, and long-term adaptation to drinking. One group of adult male Sprague-Dawley rats was treated with ethanol vapor and the other given room air. After 3 wk the rats received i.v. [2-(13)C]ethanol and [1, 2-(13)C2]acetate for 2 h, and then the brain was fixed, removed, and divided into neocortex and subcortical tissues for measurement of (13)C isotopic labeling of glutamate and glutamine by magnetic resonance spectroscopy. Ethanol oxidation was seen to occur both in the cortex and the subcortex. In ethanol-naïve rats, cortical oxidation of ethanol occurred at rates of 0.017 ± 0.002 µmol/min/g in astroglia and 0.014 ± 0.003 µmol/min/g in neurons, and chronic alcohol exposure increased the astroglial ethanol oxidation to 0.028 ± 0.002 µmol/min/g (P = 0.001) with an insignificant effect on neuronal ethanol oxidation. Compared with published rates of overall oxidative metabolism in astroglia and neurons, ethanol provided 12.3 ± 1.4% of cortical astroglial oxidation in ethanol-naïve rats and 20.2 ± 1.5% in ethanol-treated rats. For cortical astroglia and neurons combined, the ethanol oxidation for naïve and treated rats was 3.2 ± 0.3% and 3.8 ± 0.2% of total oxidation, respectively. (13)C labeling from subcortical oxidation of ethanol was similar to that seen in cortex but was not affected by chronic ethanol exposure.

Acquisition and reconditioning of ethanol-induced conditioned place preference in mice is blocked by the H₂O₂ scavenger alpha lipoic acid

RATIONALE

Hydrogen peroxide (H2O2) is the co-substrate used by catalase to metabolize ethanol to acetaldehyde in the brain. This centrally formed acetaldehyde has been involved in several ethanol-related behaviors.

OBJECTIVES

The present research evaluated the effect of the H2O2 scavenger, alpha lipoic acid (LA), on the acquisition and reconditioning of ethanol-induced conditioned place preference (CPP).

METHODS

Mice received pairings of a distinctive floor stimulus (CS+) associated with intraperitoneal injections of ethanol (2.5 g/kg). On alternate days, animals received pairings of a different floor stimulus (CS-) associated with saline injections. A different group of animals received pairings with the (CS-) associated with saline injections, and on alternate days they received LA (100 mg/kg) injected 30 min prior to ethanol (2.5 g/kg) administration paired with the (CS+). A preference test assessed the effect of LA on the acquisition of ethanol-induced CPP. A similar procedure was followed to study the effect of LA on the acquisition of cocaine- and morphine-induced CPP. A separate experiment evaluated the effect of LA on the reconditioning of ethanol-induced CPP. In addition, we investigated the consequence of LA administration on central H2O2 levels.

RESULTS

LA selectively blocked the acquisition of ethanol-induced CPP. Moreover, this compound impaired the reconditioning of ethanol-induced CPP. Additionally, we found that LA diminished H2O2 levels in the brain.

CONCLUSIONS

These data suggest that a decline in H2O2 availability by LA might impede the formation of brain ethanol-derived acetaldehyde by catalase, which results in an impairment of the rewarding properties of ethanol.

Increased levels of monoamine-derived potential neurotoxins in fetal rat brain exposed to ethanol

Pregnant SD rats were exposed to ethanol (25 % (v/v) ethanol at 1.0, 2.0 or 4.0 g/kg body weight from GD8 to GD20) to assess whether ethanol-derived acetaldehyde could interact with endogenous monoamine to generate tetrahydroisoquinoline or tetrahydro-beta-carboline in the fetuses. The fetal brain concentration of acetaldehyde increased remarkably after ethanol administration (2.6 times, 5.3 times and 7.8 times as compared to saline control in 1.0, 2.0 and 4.0 g/kg ethanol-treated groups, respectively) detected by HPLC with 2,4-dinitrophenylhydrazine derivatization. Compared to control, ethanol exposure induced the formation of 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol, Sal), N-methyl-salsolinol (NMSal) and 1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline (6-OH-MTHBC) in fetal rat brains. Determined by HPLC with electrochemical detector, the levels of dopamine and 5-hydroxytryptamine in whole fetal brain were not remarkably altered by ethanol treatment, while the levels of homovanillic acid and 5-hydroxyindole acetic acid in high dose (4.0 g/kg) of ethanol-treated rats were significantly decreased compared to that in the control animals. 4.0 g/kg ethanol administration inhibited the activity of mitochondrial monoamine oxidase (51.3 % as compared to control) and reduced the activity of respiratory chain complex I (61.2 % as compared to control). These results suggested that ethanol-induced alteration of monoamine metabolism and the accumulation of dopamine-derived catechol isoquinolines and 5-hydroxytryptamine-derived tetrahydro-beta-carbolines may play roles in the developmental dysfuction of monoaminergic neuronal systems.

Ethanol-induced disruption of Golgi apparatus morphology, primary neurite number and cellular orientation in developing cortical neurons

Prenatal ethanol exposure disrupts cortical neurite initiation and outgrowth, but prior studies have reported both ethanol-dependent growth promotion and inhibition. To resolve this ambiguity and better approximate in vivo conditions, we quantitatively analyzed neuronal morphology using a new, whole hemisphere explant model. In this model, Layer 6 (L6) cortical neurons migrate, laminate and extend neurites in an organotypic fashion. To selectively label L6 neurons, we performed ex utero electroporation of a GFP expression construct at embryonic day 13 and allowed the explants to develop for 2 days in vitro. Explants were exposed to (400 mg/dL) ethanol for either 4 or 24 h prior to fixation. Complete 3-D reconstructions were made of >80 GFP-positive neurons in each experimental condition. Acute responses to ethanol exposure included compaction of the Golgi apparatus accompanied by elaboration of supernumerary primary apical neurites, as well as a modest (∼15%) increase in higher order apical neurite length. With longer exposure time, ethanol exposure leads to a consistent, significant disorientation of the cell (cell body, primary apical neurite, and Golgi) with respect to the pial surface. The effects on cellular orientation were accompanied by decreased expression of cytoskeletal elements, microtubule-associated protein 2 and F-actin. These findings indicate that upon exposure to ethanol, developing L6 neurons manifest disruptions in Golgi apparatus and cytoskeletal elements which may in turn trigger selective and significant perturbations to primary neurite formation and neuronal polarity.

The H2O2 scavenger ebselen decreases ethanol-induced locomotor stimulation in mice

BACKGROUND

In the brain, the enzyme catalase by reacting with H(2)O(2) forms Compound I (catalase-H(2)O(2) system), which is the main system of central ethanol metabolism to acetaldehyde. Previous research has demonstrated that acetaldehyde derived from central-ethanol metabolism mediates some of the psychopharmacological effects produced by ethanol. Manipulations that modulate central catalase activity or sequester acetaldehyde after ethanol administration modify the stimulant effects induced by ethanol in mice. However, the role of H(2)O(2) in the behavioral effects caused by ethanol has not been clearly addressed. The present study investigated the effects of ebselen, an H(2)O(2) scavenger, on ethanol-induced locomotion.

METHODS

Swiss RjOrl mice were pre-treated with ebselen (0-50mg/kg) intraperitoneally (IP) prior to administration of ethanol (0-3.75g/kg; IP). In another experiment, animals were pre-treated with ebselen (0 or 25mg/kg; IP) before caffeine (15mg/kg; IP), amphetamine (2mg/kg; IP) or cocaine (10mg/kg; IP) administration. Following these treatments, animals were placed in an open field to measure their locomotor activity. Additionally, we evaluated the effect of ebselen on the H(2)O(2)-mediated inactivation of brain catalase activity by 3-amino-1,2,4-triazole (AT).

RESULTS

Ebselen selectively prevented ethanol-induced locomotor stimulation without altering the baseline activity or the locomotor stimulating effects caused by caffeine, amphetamine and cocaine. Ebselen reduced the ability of AT to inhibit brain catalase activity.

CONCLUSIONS

Taken together, these data suggest that a decline in H(2)O(2) levels might result in a reduction of the ethanol locomotor-stimulating effects, indicating a possible role for H(2)O(2) in some of the psychopharmacological effects produced by ethanol.

Acetaldehyde oral self-administration: evidence from the operant-conflict paradigm

BACKGROUND

Acetaldehyde (ACD), ethanol's first metabolite, has been reported to interact with the dopaminergic reward system, and with the neural circuits involved in stress response. Rats self-administer ACD directly into cerebral ventricles, and multiple intracerebroventricular infusions of ACD produce conditioned place preference. Self-administration has been largely employed to assess the reinforcing and addictive properties of most drugs of abuse. In particular, operant conditioning is a valid model to investigate drug-seeking and drug-taking behavior in rats.

METHODS

This study was aimed at the evaluation of (i) the motivational properties of oral ACD in the induction and maintenance of an operant-drinking behavior; (ii) ACD effect in a conflict situation employing the punishment-based Geller-Seifter procedure; and (iii) the onset of a relapse drinking behavior, following ACD deprivation. The lever-pressing procedure in a sound-attenuated operant-conditioning chamber was scheduled into 3 different periods: (i) training-rewarded responses with a fixed ratio 1; (ii) conflict-rewarded responses periodically associated with a 0.2 mA foot-shock; and (iii) relapse-rewarded lever presses following 1-week ACD abstinence.

RESULTS

Our results show that oral self-administrated ACD induced: a higher rate of punished responses in Geller-Seifter procedures; and the establishment of a relapse behavior following ACD deprivation.

CONCLUSIONS

In conclusion, our results indicate that ACD is able to induce an operant-drinking behavior, which is also maintained besides the conflict procedure and enhanced by the deprivation effect, supporting the hypothesis that ACD itself possesses motivational properties, such as alcohol and other substances of abuse.

α-Lipoic acid, a scavenging agent for H₂O₂, reduces ethanol-stimulated locomotion in mice

RATIONALE

The main system of central ethanol oxidation is mediated by the enzyme catalase. By reacting with H(2)O(2), brain catalase forms compound I (the catalase-H(2)O(2) system), which is able to oxidize ethanol to acetaldehyde in the brain. Previous studies have demonstrated that pharmacological manipulations of brain catalase activity modulate the stimulant effects of ethanol in mice. However, the role of H(2)O(2) in the behavioral effects of ethanol has not yet been clearly addressed.

OBJECTIVES

In the present study, we investigated the effects of alpha-lipoic acid (LA), a scavenging agent for H(2)O(2), on ethanol-induced locomotor stimulation.

METHODS

CD-1 mice were pretreated with LA [0-100 mg/kg, intraperitoneally (IP)] 0-60 min prior to administration of ethanol (0-3.75 g/kg, IP). In another experiment, animals were pretreated with LA (0, 25, or 50 mg/kg, IP) 30 min before cocaine (10 mg/kg, IP), amphetamine (2 mg/kg, IP), or caffeine (25 mg/kg, IP). After these treatments the animals were placed in an open-field chamber and their locomotor activity was measured for 20 min.

RESULTS

LA 25, 50, and 100 mg/kg IP prevented ethanol-induced locomotor stimulation. LA did not affect the locomotor-stimulating effects of cocaine, amphetamine, and caffeine. Additionally, we demonstrated that LA prevents the inactivation of brain catalase by 3-amino-1,2,4-triazole, thus indicating that H(2)O(2) levels are reduced by LA.

CONCLUSIONS

These data support the idea that a decrease in cerebral H(2)O(2) production by LA administration inhibits ethanol-stimulated locomotion. This study suggests that the brain catalase-H(2)O(2) system, and by implication centrally formed acetaldehyde, plays a key role in the psychopharmacological effects of ethanol.

An optimized method for the measurement of acetaldehyde by high-performance liquid chromatography

BACKGROUND

Acetaldehyde is produced during ethanol metabolism predominantly in the liver by alcohol dehydrogenase and rapidly eliminated by oxidation to acetate via aldehyde dehydrogenase. Assessment of circulating acetaldehyde levels in biological matrices is performed by headspace gas chromatography and reverse phase high-performance liquid chromatography (RP-HPLC).

METHODS

We have developed an optimized method for the measurement of acetaldehyde by RP-HPLC in hepatoma cell culture medium, blood, and plasma. After sample deproteinization, acetaldehyde was derivatized with 2,4-dinitrophenylhydrazine (DNPH). The reaction was optimized for pH, amount of derivatization reagent, time, and temperature. Extraction methods of the acetaldehyde-hydrazone (AcH-DNP) stable derivative and product stability studies were carried out. Acetaldehyde was identified by its retention time in comparison with AcH-DNP standard, using a new chromatography gradient program, and quantitated based on external reference standards and standard addition calibration curves in the presence and absence of ethanol.

RESULTS

Derivatization of acetaldehyde was performed at pH 4.0 with an 80-fold molar excess of DNPH. The reaction was completed in 40 minutes at ambient temperature, and the product was stable for 2 days. A clear separation of AcH-DNP from DNPH was obtained with a new 11-minute chromatography program. Acetaldehyde detection was linear up to 80 μM. The recovery of acetaldehyde was >88% in culture media and >78% in plasma. We quantitatively determined the ethanol-derived acetaldehyde in hepatoma cells, rat blood and plasma with a detection limit around 3 μM. The accuracy of the method was <9% for intraday and <15% for interday measurements, in small volume (70 μl) plasma sampling.

CONCLUSIONS

An optimized method for the quantitative determination of acetaldehyde in biological systems was developed using derivatization with DNPH, followed by a short RP-HPLC separation of AcH-DNP. The method has an extended linear range, is reproducible and applicable to small-volume sampling of culture media and biological fluids.

The role of oxidative stress in fetal alcohol spectrum disorders

The ingestion of alcohol/ethanol during pregnancy can result in abnormal fetal development in both humans and a variety of experimental animal models. Depending on the pattern of consumption, the dose, and the period of exposure to ethanol, a myriad of structural and functional deficits can be observed. These teratogenic effects are thought to result from the ethanol-induced dysregulation of a variety of intracellular pathways ultimately culminating in toxicity and cell death. For instance, ethanol exposure can lead to the generation of reactive oxygen species (ROS) and produce an imbalance in the intracellular redox state, leading to an overall increase in oxidative stress. In the present review we will provide an up-to-date summary on the effects of prenatal/neonatal ethanol exposure on the levels of oxidative stress in the central nervous system (CNS) of experimental models of fetal alcohol spectrum disorders (FASD). We will also review the evidence for the use of antioxidants as potential therapeutic strategies for the treatment of some of the neuropathological deficits characteristic of both rodent models of FASD and children afflicted with these disorders. We conclude that an imbalance in the intracellular redox state contributes to the deficits seen in FASD and suggest that antioxidants are potential candidates for the development of novel therapeutic strategies for the treatment of these developmental disorders.

Ethanol as a prodrug: brain metabolism of ethanol mediates its reinforcing effects--a commentary

BACKGROUND

This commentary discusses a study by Karahanian and colleagues (2011) on the role of central nervous system acetaldehyde in the reinforcing effects of ethanol. The goal is to emphasize the importance of the study and to discuss future directions.

RESULTS

This important paper solidifies the idea that the levels of acetaldehyde in the central nervous system have profound effects in mediating the reinforcing actions of ethanol. This is accomplished by manipulating the brain levels of acetaldehyde produced from ethanol by the injection of lentivirus containing either an anti-catalase shRNA construct or a rat liver alcohol dehydrogenase into the central nervous system and observing the effects on alcohol preference by high ethanol-consuming rats. A factor not directly considered is that acetaldehyde is further metabolized to acetate, which also has some behavioral actions.

CONCLUSIONS

The efficacy of lentivirus injections of enzyme inhibitors or enzymes themselves to alter a behavioral response to ethanol is clearly demonstrated here. The many other actions of ethanol that are postulated to be a result of the production of acetaldehyde in the brain remain to be investigated by similar techniques. Possible "therapeutic avenues to reduce chronic alcohol use" are envisioned.

Human catalase: looking for complete identity

Catalases are well studied enzymes that play critical roles in protecting cells against the toxic effects of hydrogen peroxide. The ubiquity of the enzyme and the availability of substrates made heme catalases the focus of many biochemical and molecular biology studies over 100 years. In human, this has been implicated in various physiological and pathological conditions. Advancement in proteomics revealed many of novel and previously unknown features of this mysterious enzyme, but some functional aspects are yet to be explained. Along with discussion on future research area, this mini-review compile the information available on the structure, function and mechanism of action of human catalase.

Ethanol modulates corticotropin releasing hormone release from the rat hypothalamus: does acetaldehyde play a role?

BACKGROUND AND METHODS

Ethanol (EtOH) activates hypothalamic-pituitary-adrenal (HPA) axis, resulting in adrenocorticotropin hormone, glucocorticoid release, and in modifications of the response of the axis to other stressors. The initial site of EtOH action within the HPA system seems to be the hypothalamus. Thus, to determine the mechanisms responsible for these effects, we investigated: (i) whether EtOH was able to release corticotrophic releasing hormone (CRH) from incubated hypothalamic explants; (ii) whether acetaldehyde (ACD), its first metabolite formed in the brain by catalase activity, might play a role in EtOH activity. To this aim, rat hypothalamic explants were incubated with: (i) medium containing EtOH at 32.6 x 10(3) microM; (ii) different concentration of ACD (1, 3, 10, and 30 microM); (iii) EtOH plus 3amino-1,2,4-triazole (3AT, 32 x 10(3) microM) an inhibitor of cerebral catalase; (iv) ACD plus D-penicillamine (DP, 50.3 x 10(3) microM) an ACD-trapping agent. CRH levels were evaluated by a radioimmunoassay.

RESULTS

Incubation with EtOH induced a 7-fold increase in CRH secretion, with respect to basal levels; ACD was able to stimulate CRH release in a dose-dependent manner; the inhibition of cerebral catalase by 3AT blocked EtOH-induced CRH outflow; the inactivation of ACD by DP reverted the ACD-stimulating effect on CRH secretion.

CONCLUSIONS

These data show that both EtOH and acetaldehyde are able to increase hypothalamic CRH release from the rat hypothalamus and that acetaldehyde itself appears to be the mediator of EtOH activity.

A low ethanol dose affects all types of cells in mixed long-term embryonic cultures of the cerebellum

The beneficial effect of the '1-drink-a-day' lifestyle is suggested by studies of cardiovascular health, and this recommendation is increasingly followed in many countries. The main objective of this study was to determine whether this pattern of ethanol use would be detrimental to a pregnant woman. We exposed a primary culture of rat cerebellum from embryonic day 17 (corresponding to second trimester in humans) to ethanol at a concentration of 17.6 mM which is roughly equivalent to one glass of wine. Acutely, there was no change in cell viability after 5 or 8 days of exposure relative to control. By 11 days, a reduction in the number of viable cells was observed without an accompanying change in caspase-3 activity (marker of apoptotic cell death), suggesting changes in cell proliferation. As the proportion of nestin-positive cells was higher in the ethanol-treated cultures after 5 days, we hypothesized that an increase in differentiation to neurons would compensate for the ongoing neuronal death. However, there were limits to this compensatory ability as the relative proportion of nestin-positive cells was decreased after 11 days. To further illustrate the negative long-term effects of this ethanol dose, cultures were exposed for 30 days. After this period, virtually no neurons or myelinating oligodendrocytes were present in the ethanol-treated cultures. In conclusion, chronic exposure to ethanol, even at small doses, dramatically and persistently affects normal development.

Glutathione content as a potential mediator of the vulnerability of cultured fetal cortical neurons to ethanol-induced apoptosis

Ethanol ingestion during pregnancy elicits damage to the developing brain, some of which appears to result from enhanced apoptotic death of neurons. A consistent characteristic of this phenomenon is a highly differing sensitivity to ethanol within specific neuron populations. One possible explanation for this "selective vulnerability" could be cellular variations in glutathione (GSH) homeostasis. Prior studies have illustrated that ethanol elicits apoptotic death of neurons in the developing brain, that oxidative stress may be an underlying mechanism, and that GSH can be neuroprotective. In the present study, both multiphoton microscopy and flow cytometry demonstrate a striking heterogeneity in GSH content within cortical neuron populations. Ethanol differentially elicits apoptotic death and oxidative stress in these neurons. When neuron GSH content is reduced by treatment with butathione sulfoxamine, the ethanol-mediated enhancement of reactive oxygen species is exacerbated. Sorting of cells into high- and low-GSH populations further exemplifies ethanol-mediated oxidative stress whereby apoptotic indices are preferentially elevated in the low-GSH population. Western blot analysis of the low-GSH subpopulations shows higher ethanol-mediated expression of active caspase 3 and 24-kDa PARP-1 fragments compared with the high-GSH subpopulation. In addition, neuronal content of 4-hydroxynonenal adducts is higher in low-GSH neurons in response to ethanol. These studies suggest that GSH content is an important predictor of neuronal sensitivity to ethanol-mediated oxidative stress and subsequent cell death. The data support the proposition that the differences in proapoptotic responses to ethanol within specific neuron populations reflect a heterogeneity of neuron GSH content.

The reinforcing properties of salsolinol in the ventral tegmental area: evidence for regional heterogeneity and the involvement of serotonin and dopamine

BACKGROUND

Salsolinol (SAL), the condensation product of acetaldehyde and dopamine, may be a factor contributing to alcohol abuse. Previous research indicated that both ethanol and acetaldehyde are self-administered into the posterior ventral tegmental area (VTA). The current study examined SAL self-infusions into the VTA, and determined the involvement of dopamine neurons and 5-HT3 receptors in this process.

METHODS

The intracranial self-administration technique was used to determine the self-infusion of SAL into the VTA of adult, male Wistar rats. The rats were placed in 2-lever (active and inactive) experimental chambers, and allowed to respond for the self-infusion of 0, 0.03, 0.1, 0.3, 1.0 or 3.0 microM SAL into the posterior or anterior VTA. In a second experiment, rats self-administered 0.3 microM SAL for the initial 4 sessions, co-administered SAL with ICS-205,930 (a 5-HT3 receptor antagonist) or quinpirole (a D(2,3) receptor agonist) for sessions 5 and 6, and then only 0.3 microM SAL for session 7.

RESULTS

Wistar rats, given 0.03 to 0.3 microM SAL, received more infusions per session than did the group given artificial cerebrospinal fluid (aCSF) alone (e.g., 41 infusions for 0.1 microM SAL versus 9 infusions for the aCSF group), and responded more on the active than inactive lever. These effects were observed in the posterior but not in anterior VTA. Co-infusion of 100 microM ICS-205,930, or quinpirole significantly reduced self-infusions and active lever responding.

CONCLUSIONS

SAL produces reinforcing effects in the posterior VTA of Wistar rats, and these effects are mediated by activation of DA neurons and local 5-HT3 receptors.

Involvement of brain catalase activity in the acquisition of ethanol-induced conditioned place preference

It has been suggested that some of the behavioral effects produced by ethanol are mediated by its first metabolite, acetaldehyde. The present research addressed the hypothesis that catalase-dependent metabolism of ethanol to acetaldehyde in the brain is an important step in the production of ethanol-related affective properties. Firstly, we investigated the contribution of brain catalase in the acquisition of ethanol-induced conditioned place preference (CPP). Secondly, the specificity of the catalase inhibitor 3-amino-1,2,4-triazole (AT) was evaluated with morphine- and cocaine-induced CPP. Finally, to investigate the role of catalase in the process of relapse to ethanol seeking caused by re-exposure to ethanol, after an initial conditioning and extinction, mice were primed with saline and ethanol or AT and ethanol and tested for reinstatement of CPP. Conditioned place preference was blocked in animals treated with AT and ethanol. Morphine and cocaine CPP were unaffected by AT treatment. However, the reinstatement of place preference was not modified by catalase inhibition. Taken together, the results of the present study indicate that the brain catalase-H(2)O(2) system contributes to the acquisition of affective-dependent learning induced by ethanol, and support the involvement of centrally-formed acetaldehyde in the formation of positive affective memories produced by ethanol.

Central reinforcing effects of ethanol are blocked by catalase inhibition

Recent studies have systematically indicated that newborn rats are highly sensitive to ethanol's positive reinforcing effects. Central administrations of ethanol (25-200mg %) associated with an olfactory conditioned stimulus (CS) promote subsequent conditioned approach to the CS as evaluated through the newborn's response to a surrogate nipple scented with the CS. It has been shown that ethanol's first metabolite, acetaldehyde, exerts significant reinforcing effects in the central nervous system. A significant amount of acetaldehyde is derived from ethanol metabolism via the catalase system. In newborn rats, catalase levels are particularly high in several brain structures. The present study tested the effect of catalase inhibition on central ethanol reinforcement. In the first experiment, pups experienced lemon odor either paired or unpaired with intracisternal (IC) administrations of 100mg% ethanol. Half of the animals corresponding to each learning condition were pretreated with IC administrations of either physiological saline or a catalase inhibitor (sodium-azide). Catalase inhibition completely suppressed ethanol reinforcement in paired groups without affecting responsiveness to the CS during conditioning or responding by unpaired control groups. A second experiment tested whether these effects were specific to ethanol reinforcement or due instead to general impairment in learning and expression capabilities. Central administration of an endogenous kappa opioid receptor agonist (dynorphin A-13) was used as an alternative source of reinforcement. Inhibition of the catalase system had no effect on the reinforcing properties of dynorphin. The present results support the hypothesis that ethanol metabolism regulated by the catalase system plays a critical role in determination of ethanol reinforcement in newborn rats.

Ethanol oxidation in the living brain

AIM

The examination of the possibility of ethanol oxidation in the brain in vivo and the evaluation of the enzyme catalase in this process.

METHODS

We anesthetized rats and perfused the brain with ethanol solutions through the lateral ventricle and collected the perfusate from the Cisterna magna. We determined ethanol and acetaldehyde in the perfusate by gas chromatography.

RESULTS

It was found that the passage of ethanol solution (85 and 90 mM) through the ventricular system of the rat brain (6-43 microl/min) results in the significant (up to 98%) elimination of ethanol from the perfusing fluid and in the appearance of acetaldehyde (up-to 60 microM) in the perfusate. The addition of the catalase inhibitor, aminotriazole, (10 mM) to the perfusing fluid decreased ethanol elimination significantly.

CONCLUSIONS

The ethanol oxidation and AA accumulation take place in the living brain. The enzyme catalase is involved in this process.

A novel method for evaluation of ethanol oxidation in living brain

We propose a method for intravital examination of ethanol metabolism in rat brain. Calipsol-anesthetized rats were fixed in stereotaxis and ethanol solution was infused into the lateral cerebral ventricle via an orifice in the skull at a constant rate with a syringe or micro-pump. Elimination of ethanol and production of acetaldehyde (ethanol metabolite) were measured in perfusate samples from the cisterna magna by gas chromatography. The method is highly sensitive, reliable, and reproducible and allows to study the kinetics and enzyme mechanisms of ethanol oxidation in the brain and regulation of this process.

Ethanol and acetaldehyde induce similar changes in extracellular levels of glutamate, taurine and GABA in rat anterior cingulate cortex

It is controversial regarding to the roles of acetaldehyde and ethanol in the central nervous system. In the present study, the effects of acetaldehyde and ethanol on extracellular levels of glutamate, taurine and GABA in the anterior cingulate cortex (ACC) of freely moving rats were investigated by using the microdialysis technique coupled to high performance liquid chromatography (HPLC) with fluorescent detection. The result showed that glutamate levels were significantly decreased after acute administration of acetaldehyde (AcH, 20 and 100 mg/kg, i.p.), while taurine levels were significantly increased after the higher dose of acetaldehyde (100 mg/kg, i.p.). GABA levels had no changes at any doses of acetaldehyde tested. Interestingly, similar changes of these amino acids were induced by ethanol (EtOH, 3 g/kg, i.p.) when sodium azide (NaN3, 10 mg/kg, i.p.), a catalase inhibitor that can reduce brain ethanol metabolism, was used simultaneously. These findings suggest that acetaldehyde and ethanol have the similar effects on the extracellular output of glutamate, taurine and GABA in the ACC.

Acute administration of 3-nitropropionic acid, a reactive oxygen species generator, boosts ethanol-induced locomotor stimulation. New support for the role of brain catalase in the behavioural effects of ethanol

The antioxidant enzyme catalase by reacting with H(2)O(2), forms the compound known as compound I (catalase-H(2)O(2)). This compound is able to oxidise ethanol to acetaldehyde in the CNS. It has been demonstrated that 3-nitropropionic acid (3-NPA) induces the activity of the brain catalase-H(2)O(2) system. In this study, we tested the effect of 3-NPA on both the brain catalase-H(2)O(2) system and on the acute locomotor effect of ethanol. To find the optimal interval for the 3-NPA-ethanol interaction mice were treated with 3-NPA 0, 45, 90 and 135min before an ethanol injection (2.4mg/kg). In a second study, 3-NPA (0, 15, 30 or 45mg/kg) was administered SC to animals 90min before saline or several doses of ethanol (1.6 or 2.4g/kg), and the open-field behaviour was registered. The specificity of the effect of 3-NPA (45mg/kg) was evaluated on caffeine (10mg/kg IP) and cocaine (4mg/kg)-induced locomotion. The prevention of 3-NPA effects on both ethanol-induced locomotion and brain catalase activity by L-carnitine, a potent antioxidant, was also studied. Nitropropionic acid boosted ethanol-induced locomotion and brain catalase activity after 90min. The effect of 3-NPA was prevented by l-carnitine administration. These results indicate that 3-NPA enhanced ethanol-induced locomotion by increasing the activity of the brain catalase system.

Enzymatic mechanisms of ethanol oxidation in the brain

BACKGROUND

The exact enzymatic mechanisms of ethanol oxidation in the brain are still unclear. The catalase-mediated oxidation of ethanol was demonstrated in rat brain using incubation of brain homogenates with catalase inhibitors. The role of the alcohol dehydrogenase (ADH) or cytochrome P450-dependent system in this process is possible, but has not been confirmed. The objective of the study was to determine the contribution of the different enzymatic pathways to ethanol oxidation in brain homogenates from mice and rats.

METHODS

Three approaches were used to investigate the enzymatic mechanisms of ethanol oxidation in the brain of rats and mice: (1) preincubation of brain homogenates with inhibitors of the ethanol-metabolizing enzymes (catalase, CYP2E1, ADH, and ALDH); (2) utilization of mice with genetic deficiency in ethanol-metabolizing enzymes (catalase, CYP2E1, or both enzymes); and (3) determination of ethanol oxidation in brain subcellular fractions known to have differential activity of ethanol-metabolizing enzymes. The ethanol-derived acetaldehyde (AC) and acetate were determined in brain samples by gas chromatography.

RESULTS

The catalase inhibitors sodium azide (5 mM) and aminotriazole (5 mM) as well as CYP2E1 inhibitors diallyl sulfide (2 mM) and beta-phenethyl isothiocyanate (0.1 mM) lowered significantly the accumulation of the ethanol-derived AC and acetate in brain homogenates. The ADH inhibitor 4-methyl pyrazole (5 mM) significantly decreased the acetate but not the AC accumulation. Ethanol-derived AC accumulation in brain homogenates of acatalasemic mice was 47% of the control value, 91% in CYP2E1-null mice, and 24% in double mutants (with deficiency of both catalase and CYP2E1). The highest levels of ethanol oxidation were found in microsomal and peroxisomal subcellular brain fractions, where CYP2E1 and catalase are located, respectively.

CONCLUSIONS

Catalase is the key enzyme of ethanol oxidation in the brain of rodents: it may be responsible for about 60% of the process. CYP2E1 plays an important role in ethanol oxidation in the rodent brains. Alcohol dehydrogenase plays a minor role, if any, in this process. Aldehyde dehydrogenase plays the crucial role in the further oxidation of ethanol-derived AC in the brain homogenates.

Does ascorbate/L-Cys/L-Met mixture protect different parts of the rat brain against chronic alcohol toxicity?

Chronic ingestion of high levels of alcohol may cause oxidative stress that results in the formation, through alcohol metabolism, of excess free radicals, acetaldehyde, lipid and protein oxidation, and their reactivity products. These harmful molecules may trigger oxidative damage to neurons and can cause cell death. It is hypothesized that cysteine-methionine and vitamin C may neutralize these harmful compounds while potentiating the antioxidant capacity of the cell or tissue. In the present study, rats were fed regular diets and were maintained for 90 days in (1) the control group, (2) the alcoholic group, which was given 2.5 g of 50% ethanol/kg body weight administered intragastrically every other day, or (3) the alcoholic with antioxidant supplement group, to whom 2.5 g of 50% ethanol/kg body weight + a solution that contained 200 mg vitamin C, 100 mg cysteine, and 100 mg methionine was administered intragastrically every other day. The mean blood alcohol level was raised by 40% in the alcoholic group compared with the control group, but, compared with the alcoholic group, the alcohol level was decreased by 30% in the antioxidant-supplemented group. In keeping with blood alcohol levels, oxidized protein and lipid content in the cerebrum, brain stem, and cerebellum were low in the control group, higher in the antioxidant-supplemented group, and highest in the alcoholic group. The mean total thiol level was higher in the antioxidant-supplemented group than in the alcoholic and control groups. It is interesting to note that the level of total glutathione in the cerebrum and cerebellum in the alcoholic group was lower than in the control and antioxidant-supplemented groups. In conclusion, long-term alcohol administration led to increased levels of oxidized protein and lipids in the cerebrum, brain stem, and cerebellum of rats. Simultaneous intake of ascorbate/l-cys/l-met and ethanol attenuated the amount of oxidation that occurred, which suggested that cysteine, methionine, and vitamin C may play a protective role in the central nervous system against oxidative damage caused by alcohol consumption. In addition, the mean alcohol level was increased in the alcoholic group compared with the control group. The level of total glutathione was significantly decreased in the cerebellum of the alcoholic group, and oxidative damage was noted in various parts of the brain in this group. These findings suggest that oxidative stress plays a pathogenetic role in brain damage related to chronic alcoholism.

The UChA and UChB rat lines: metabolic and genetic differences influencing ethanol intake

Ethanol non-drinker (UChA) and drinker (UChB) rat lines derived from an original Wistar colony have been selectively bred at the University of Chile for over 70 generations. Two main differences between these lines are clear. (1) Drinker rats display a markedly faster acute tolerance than non-drinker rats. In F2 UChA x UChB rats (in which all genes are 'shuffled'), a high acute tolerance of the offspring predicts higher drinking than a low acute tolerance. It is further shown that high-drinker animals 'learn' to drink, starting from consumption levels that are one half of the maximum consumptions reached after 1 month of unrestricted access to 10% ethanol and water. It is likely that acquired tolerance is at the basis of the increases in ethanol consumption over time. (2) Non-drinker rats carry a previously unreported allele of aldehyde dehydrogenase-2 (Aldh2) that encodes an enzyme with a low affinity for Nicotinamide-adenine-dinuclectide (NAD+) (Aldh2(2)), while drinker rats present two Aldh2 alleles (Aldh2(1) and Aldh2(3)) with four- to fivefold higher affinities for NAD+. Further, the ALDH2 encoded by Aldh2(1) also shows a 33% higher Vmax than those encoded by Aldh2(2) and Aldh2(3). Maximal voluntary ethanol intakes are the following: UChA Aldh2(2)/Aldh2(2) = 0.3-0.6 g/kg/day; UChB Aldh2(3)/Aldh2(3) = 4.5-5.0 g/kg/day; UChB Aldh2(1)/Aldh2(1) = 7.0-7.5 g/kg/day. In F2 offspring of UChA x UChB, the Aldh2(2)/Aldh2(2) genotype predicts a 40-60% of the alcohol consumption. Studies also show that the low alcohol consumption phenotype of Aldh2(2)/Aldh2(2) animals depends on the existence of a maternally derived low-activity mitochondrial reduced form of nicotinamide-adenine-dinucleotide (NADH)-ubiquinone complex I. The latter does not influence ethanol consumption of animals exhibiting an ALDH2 with a higher affinity for NAD+. An illuminating finding is the existence of an 'acetaldehyde burst' in animals with a low capacity to oxidize acetaldehyde, being fivefold higher in UChA than in UChB animals. We propose that such a burst results from a great generation of acetaldehyde by alcohol dehydrogenase in pre-steady-state conditions that is not met by the high rate of acetaldehyde oxidation in mitochondria. The acetaldehyde burst is seen despite the lack of differences between UChA and UChB rats in acetaldehyde levels or rates of alcohol metabolism in steady state. Inferences are drawn as to how these studies might explain the protection against alcoholism seen in humans that carry the high-activity alcohol dehydrogenase but metabolize ethanol at about normal rates.