Perinatal ethanol exposure affects cell populations in adult dorsal hippocampal neurogenic niche

Neurodevelopment is highly affected by perinatal ethanol exposure (PEE). In the adult brain, neurogenesis takes place in the dentate gyrus (DG) of the hippocampus and in the subventricular zone. This work aimed to analyze the effect of PEE on the cellular types involved in adult dorsal hippocampal neurogenesis phases using a murine model. For this purpose, primiparous female CD1 mice consumed only ethanol 6% v/v from 20 days prior to mating and along pregnancy and lactation to ensure that the pups were exposed to ethanol throughout pre- and early postnatal development. After weaning, pups had no further contact with ethanol. Cell types of the adult male dorsal DG were studied by immunofluorescence. A lower percentage of type 1 cells and immature neurons and a higher percentage of type 2 cells were observed in PEE animals. This decrease in type 1 cells suggests that PEE reduces the population of remnant progenitors of the dorsal DG present in adulthood. The increase in type 2 cells and the decrease in immature neurons indicate that, during neurodevelopment, ethanol alters the capacity of neuroblasts to become neurons in the adult neurogenic niche. These results suggest that pathways implicated in cell determination are affected by PEE and remain affected in adulthood.

Differential Early Mechanistic Frontal Lobe Responses to Choline Chloride and Soy Isoflavones in an Experimental Model of Fetal Alcohol Spectrum Disorder

Fetal alcohol spectrum disorder (FASD) is the most common preventable cause of neurodevelopmental defects, and white matter is a major target of ethanol neurotoxicity. Therapeutic interventions with choline or dietary soy could potentially supplement public health preventive measures. However, since soy contains abundant choline, it would be important to know if its benefits are mediated by choline or isoflavones. We compared early mechanistic responses to choline and the Daidzein+Genistein (D+G) soy isoflavones in an FASD model using frontal lobe tissue to assess oligodendrocyte function and Akt-mTOR signaling. Long Evans rat pups were binge administered 2 g/Kg of ethanol or saline (control) on postnatal days P3 and P5. P7 frontal lobe slice cultures were treated with vehicle (Veh), Choline chloride (Chol; 75 µM), or D+G (1 µM each) for 72 h without further ethanol exposures. The expression levels of myelin oligodendrocyte proteins and stress-related molecules were measured by duplex enzyme-linked immunosorbent assays (ELISAs), and mTOR signaling proteins and phosphoproteins were assessed using 11-plex magnetic bead-based ELISAs. Ethanol's main short-term effects in Veh-treated cultures were to increase GFAP and relative PTEN phosphorylation and reduce Akt phosphorylation. Chol and D+G significantly modulated the expression of oligodendrocyte myelin proteins and mediators of insulin/IGF-1-Akt-mTOR signaling in both control and ethanol-exposed cultures. In general, the responses were more robust with D+G; the main exception was that RPS6 phosphorylation was significantly increased by Chol and not D+G. The findings suggest that dietary soy, with the benefits of providing complete nutrition together with Choline, could be used to help optimize neurodevelopment in humans at risk for FASD.

Cell type-specific changes in Wnt signaling and neuronal differentiation in the developing mouse cortex after prenatal alcohol exposure during neurogenesis

Fetal Alcohol Spectrum Disorder (FASD) encompasses an array of effects of prenatal alcohol exposure (PAE), including physical abnormalities and cognitive and behavioral deficits. Disruptions of cortical development have been implicated in multiple PAE studies, with deficits including decreased progenitor proliferation, disrupted neuronal differentiation, aberrant radial migration of pyramidal neurons, and decreased cortical thickness. While several mechanisms of alcohol teratogenicity have been explored, how specific cell types in the brain at different developmental time points may be differentially affected by PAE is still poorly understood. In this study, we used single nucleus RNA sequencing (snRNAseq) to investigate whether moderate PAE from neurulation through peak cortical neurogenesis induces cell type-specific transcriptomic changes in the developing murine brain. Cluster analysis identified 25 neuronal cell types, including subtypes of radial glial cells (RGCs), intermediate progenitor cells (IPCs), projection neurons, and interneurons. Only Wnt-expressing cortical hem RGCs showed a significant decrease in the percentage of cells after PAE, with no cell types showing PAE-induced apoptosis as measured by caspase expression. Cell cycle analysis revealed only a subtype of RGCs expressing the downstream Wnt signaling transcription factor Tcf7l2 had a decreased percentage of cells in the G2/M phase of the cell cycle, suggesting decreased proliferation in this RGC subtype and further implicating disrupted Wnt signaling after PAE at this early developmental timepoint. An increased pseudotime score in IPC and projection neuron cell types indicated that PAE led to increased or premature differentiation of these cells. Biological processes affected by PAE included the upregulation of pathways related to synaptic activity and neuronal differentiation and downregulation of pathways related to chromosome structure and the cell cycle. Several cell types showed a decrease in Wnt signaling pathways, with several genes related to Wnt signaling altered by PAE in multiple cell types. As Wnt has been shown to promote proliferation and inhibit differentiation at earlier stages in development, the downregulation of Wnt signaling may have resulted in premature neuronal maturation of projection neurons and their intermediate progenitors. Overall, these findings provide further insight into the cell type-specific effects of PAE during early corticogenesis.

Impact of Wnt/β-catenin signaling on ethanol-induced changes in brain endothelial cell permeability

Chronic exposure to ethanol is associated with enhanced leakiness in the brain microvessel endothelial cells that form the blood-brain barrier (BBB). As previous studies suggested Wnt/β-catenin signaling could improve the BBB phenotype of brain endothelial cells, we examined the extent to which Wnt signaling is altered following ethanol exposure, using both a cell culture model of the BBB and mice exposed to ethanol, and the ability of Wnt activation to reverse the permeability effects of ethanol. The human brain endothelial cells, hCMEC/D3, were exposed to ethanol (17-200 mM) for various periods of time (0-96 hr) and Wnt signaling, as well as expression of downstream genes influencing BBB integrity in the cell monolayers were monitored. Determination of Wnt signaling in both brain homogenates and brain microvessels from mice exposed to ethanol was also performed. The effects of ethanol on the permeability of the hCMEC/D3 monolayers were examined using both small molecular weight (sodium fluorescein) and large molecular weight (IRdye 800CW PEG) fluorescent markers. Exposure of hCMEC/D3 to ethanol (50 mM) caused a down-regulation of Wnt/β-catenin signaling, a reduction of tight junction protein expression and up-regulation of plasmalemma vesicle associated protein (PLVAP). A similar reduction in Wnt/β-catenin activity in both cortical brain homogenates and isolated cortical cerebral microvessels were observed in mice. Other areas such as cerebellum and striatum displayed as much as 3-6 fold increases in Dkk-1, an endogenous Wnt inhibitor. Ethanol exposure caused significant changes in both sodium fluorescein and IRdye 800CW PEG permeability (2-fold compared to control). The ethanol-induced increases in permeability were attenuated by treatment with known Wnt activators (i.e. LiCl or Wnt3a). Additional screens of CNS active agents with possible Wnt activity indicated fluoxetine could also prevent the permeability effects of ethanol. These studies suggest that ethanol-induced changes in brain microvessel permeability can be reversed through activation of Wnt signaling.

Postnatal Ethanol-Induced Neurodegeneration Involves CB1R-Mediated β-Catenin Degradation in Neonatal Mice

Alcohol consumption by pregnant women may produce neurological abnormalities that affect cognitive processes in children and are together defined as fetal alcohol spectrum disorders (FASDs). However, the molecular underpinnings are still poorly defined. In our earlier studies, we found that ethanol exposure of postnatal day 7 (P7) mice significantly induced widespread neurodegeneration mediated via endocannabinoids (eCBs)/cannabinoid receptor type 1 (CB1R). In the current study, we examined changes in the β-catenin protein levels that are involved in the regulation of neuronal function including neuronal death and survival. We found that moderate- and high-dose postnatal ethanol exposure (PEE) significantly reduced active-β-catenin (ABC) (non-phosphorylated form) protein levels in the hippocampus (HP) and neocortex (NC). In addition, we found that moderate- and high-dose PEE significantly increased the phosphorylated-β-catenin (p-β-catenin)/ABC ratios in the HP and NC. Antagonism/null mutation of CB1R before PEE to inhibit CC3 production mitigated the loss of ABC protein levels. Collectively, these findings demonstrated that the CB1R/β-catenin signaling mechanism causes neurodegeneration in neonatal mouse brains following PEE.

Analysis of Drosophila nervous system development following an early, brief exposure to ethanol

The effects of ethanol on neural function and development have been studied extensively, motivated in part by the addictive properties of alcohol and the neurodevelopmental deficits that arise in children with fetal alcohol spectrum disorder (FASD). Absent from this research area is a genetically tractable system to study the effects of early ethanol exposure on later neurodevelopmental and behavioral phenotypes. Here, we used embryos of the fruit fly, Drosophila melanogaster, as a model system to investigate the neuronal defects that arise after an early exposure to ethanol. We found several disruptions of neural development and morphology following a brief ethanol exposure during embryogenesis and subsequent changes in larval behavior. Altogether, this study establishes a new system to examine the effects of alcohol exposure in embryos and the potential to conduct large-scale genetics screens to uncover novel factors that sensitize or protect neurons to the effects of alcohol.

Ethanol-Induced White Matter Atrophy Is Associated with Impaired Expression of Aspartyl-Asparaginyl-β-Hydroxylase (ASPH) and Notch Signaling in an Experimental Rat Model

Alcohol-induced white matter (WM) degeneration is linked to cognitive-motor deficits and impairs insulin/insulin-like growth factor (IGF) and Notch networks regulating oligodendrocyte function. Ethanol downregulates Aspartyl-Asparaginyl-β-Hydroxylase (ASPH) which drives Notch. These experiments determined if alcohol-related WM degeneration was linked to inhibition of ASPH and Notch. Adult Long Evans rats were fed for 3, 6 or 8 weeks with liquid diets containing 26% ethanol (caloric) and in the last two weeks prior to each endpoint they were binged with 2 g/kg ethanol, 3×/week. Controls were studied in parallel. Histological sections of the frontal lobe and cerebellar vermis were used for image analysis. Frontal WM proteins were used for Western blotting and duplex ELISAs. The ethanol exposures caused progressive reductions in frontal and cerebellar WM. Ethanol-mediated frontal WM atrophy was associated with reduced expression of ASPH, Jagged 1, HES-1, and HIF-1α. These findings link ethanol-induced WM atrophy to inhibition of ASPH expression and signaling through Notch networks, including HIF-1α.

Alcohol Regulates BK Surface Expression via Wnt/β-Catenin Signaling

It has been suggested that drug tolerance represents a form of learning and memory, but this has not been experimentally established at the molecular level. We show that a component of alcohol molecular tolerance (channel internalization) from rat hippocampal neurons requires protein synthesis, in common with other forms of learning and memory. We identify β-catenin as a primary necessary protein. Alcohol increases β-catenin, and blocking accumulation of β-catenin blocks alcohol-induced internalization in these neurons. In transfected HEK293 cells, suppression of Wnt/β-catenin signaling blocks ethanol-induced internalization. Conversely, activation of Wnt/β-catenin reduces BK current density. A point mutation in a putative glycogen synthase kinase phosophorylation site within the S10 region of BK blocks internalization, suggesting that Wnt/β-catenin directly regulates alcohol-induced BK internalization via glycogen synthase kinase phosphorylation. These findings establish de novo protein synthesis and Wnt/β-catenin signaling as critical in mediating a persistent form of BK molecular alcohol tolerance establishing a commonality with other forms of long-term plasticity.

SIGNIFICANCE STATEMENT

Alcohol tolerance is a key step toward escalating alcohol consumption and subsequent dependence. Our research aims to make significant contributions toward novel, therapeutic approaches to prevent and treat alcohol misuse by understanding the molecular mechanisms of alcohol tolerance. In our current study, we identify the role of a key regulatory pathway in alcohol-induced persistent molecular changes within the hippocampus. The canonical Wnt/β-catenin pathway regulates BK channel surface expression in a protein synthesis-dependent manner reminiscent of other forms of long-term hippocampal neuronal adaptations. This unique insight opens the possibility of using clinically tested drugs, targeting the Wnt/β-catenin pathway, for the novel use of preventing and treating alcohol dependency.

Neurotrophins in the Brain: Interaction With Alcohol Exposure During Development

Fetal alcohol spectrum disorders (FASDs) are a result of the teratogenic effects of alcohol on the developing fetus. Decades of research examining both individuals with FASDs and animal models of developmental alcohol exposure have revealed the devastating effects of alcohol on brain structure, function, behavior, and cognition. Neurotrophic factors have an important role in guiding normal brain development and cellular plasticity in the adult brain. This chapter reviews the current literature showing that alcohol exposure during the developmental period impacts neurotrophin production and proposes avenues through which alcohol exposure and neurotrophin action might interact. These areas of overlap include formation of long-term potentiation, oxidative stress processes, neuroinflammation, apoptosis and cell loss, hippocampal adult neurogenesis, dendritic morphology and spine density, vasculogenesis and angiogenesis, and behaviors related to spatial memory, anxiety, and depression. Finally, we discuss how neurotrophins have the potential to act in a compensatory manner as neuroprotective molecules that can combat the deleterious effects of in utero alcohol exposure.

Prenatal Alcohol Exposure Affects Progenitor Cell Numbers in Olfactory Bulbs and Dentate Gyrus of Vervet Monkeys

Fetal alcohol exposure (FAE) alters hippocampal cell numbers in rodents and primates, and this may be due, in part, to a reduction in the number or migration of neuronal progenitor cells. The olfactory bulb exhibits substantial postnatal cellular proliferation and a rapid turnover of newly formed cells in the rostral migratory pathway, while production and migration of postnatal neurons into the dentate gyrus may be more complex. The relatively small size of the olfactory bulb, compared to the hippocampus, potentially makes this structure ideal for a rapid analysis. This study used the St. Kitts vervet monkey (Chlorocebus sabeus) to (1) investigate the normal developmental sequence of post-natal proliferation in the olfactory bulb and dentate gyrus and (2) determine the effects of naturalistic prenatal ethanol exposure on proliferation at three different ages (neonate, five months and two years). Using design-based stereology, we found an age-related decrease of actively proliferating cells in the olfactory bulb and dentate gyrus for both control and FAE groups. Furthermore, at the neonatal time point, the FAE group had fewer actively proliferating cells as compared to the control group. These data are unique with respect to fetal ethanol effects on progenitor proliferation in the primate brain and suggest that the olfactory bulb may be a useful structure for studies of cellular proliferation.

Impact of exercise and a complex environment on hippocampal dendritic morphology, Bdnf gene expression, and DNA methylation in male rat pups neonatally exposed to alcohol

Alcohol exposure in utero can result in Fetal Alcohol Spectrums Disorders (FASD). Measures of hippocampal neuroplasticity, including long-term potentiation, synaptic and dendritic organization, and adult neurogenesis, are consistently disrupted in rodent models of FASD. The current study investigated whether third trimester-equivalent binge-like alcohol exposure (AE) [postnatal days (PD) 4-9] affects dendritic morphology of immature dentate gyrus granule cells, and brain-derived neurotrophic factor (Bdnf) gene expression and DNA methylation in hippocampal tissue in adult male rats. To understand immediate impact of alcohol, DNA methylation was measured in the PD10 hippocampus. In addition, two behavioral interventions, wheel running (WR) and environmental complexity (EC), were utilized as rehabilitative therapies for alcohol-induced deficits. AE significantly decreased dendritic complexity of the immature neurons, demonstrating the long-lasting impact of neonatal alcohol exposure on dendritic morphology of immature neurons in the hippocampus. Both housing conditions robustly enhanced dendritic complexity in the AE animals. While Bdnf exon I DNA methylation was lower in the AE and sham-intubated animals compared with suckle controls on PD10, alterations to Bdnf DNA methylation and gene expression levels were not present at PD72. In control animals, exercise, but not exercise followed by housing in EC, resulted in higher levels of hippocampal Bdnf gene expression and lower DNA methylation. These studies demonstrate the long-lasting negative impact of developmental alcohol exposure on hippocampal dendritic morphology and support the implementation of exercise and complex environments as therapeutic interventions for individuals with FASD. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 708-725, 2017.

Potential Contributions of the Tobacco Nicotine-Derived Nitrosamine Ketone to White Matter Molecular Pathology in Fetal Alcohol Spectrum Disorder

Background

Fetal alcohol spectrum disorder (FASD) is associated with long-term deficits in cognitive and motor functions. Previous studies linked neurodevelopmental abnormalities to increased oxidative stress and white matter hypotrophy. However, similar effects occur with low-dose nitrosamine exposures, alcohol abuse correlates with cigarette smoking, and tobacco smoke contains tobacco-specific nitrosamines, including NNK.

Hypothesis

Tobacco smoke exposure is a co-factor in FASD.

Design

Long Evans rat pups were i.p. administered ethanol (2 g/kg) on postnatal days (P) 2, 4, 6 and/or NNK (2 mg/kg) on P3, P5, and P7 to simulate third trimester human exposures. Oligodendroglial myelin-associated, neuroglial, and relevant transcription factor mRNA transcripts were measured using targeted PCR arrays.

Results

Ethanol and NNK differentially altered the expression of immature and mature oligodendroglial, neuronal and astrocytic structural and plasticity-associated, and various transcription factor genes. NNK’s effects were broader and more pronounced than ethanol’s, and additive or synergistic effects of dual exposures impacted expression of all four categories of genes investigated.

Conclusion

Developmental exposures to alcohol and NNK (via tobacco smoke) contribute to sustained abnormalities in brain white matter structure and function via distinct but overlapping alterations in the expression of genes that regulate oligodendrocyte survival, maturation and function, neuroglial structural integrity, and synaptic plasticity. The results support the hypothesis that smoking may contribute to brain abnormalities associated with FASD.

Differential Contributions of Alcohol and Nicotine-Derived Nitrosamine Ketone (NNK) to White Matter Pathology in the Adolescent Rat Brain

AIM

Epidemiologic studies have demonstrated high rates of smoking among alcoholics, and neuroimaging studies have detected white matter atrophy and degeneration in both smokers and individuals with alcohol-related brain disease (ARBD). These findings suggest that tobacco smoke exposure may be a co-factor in ARBD. The present study examines the differential and additive effects of tobacco-specific nitrosamine (NNK) and ethanol exposures on the structural and functional integrity of white matter in an experimental model.

METHODS

Adolescent Long Evans rats were fed liquid diets containing 0 or 26% ethanol for 8 weeks. In weeks 3-8, rats were treated with nicotine-derived nitrosamine ketone (NNK) (2 mg/kg, 3×/week) or saline by i.p. injection. In weeks 7-8, the ethanol group was binge-administered ethanol (2 g/kg; 3×/week).

RESULTS

Ethanol, NNK and ethanol + NNK caused striking degenerative abnormalities in white matter myelin and axons, with accompanying reductions in myelin-associated glycoprotein expression. Quantitative RT-PCR targeted array and heatmap analyses demonstrated that ethanol modestly increased, whereas ethanol + NNK sharply increased expression of immature and mature oligodendroglial genes, and that NNK increased immature but inhibited mature oligodendroglial genes. In addition, NNK modulated expression of neuroglial genes in favor of growth cone collapse and synaptic disconnection. Ethanol- and NNK-associated increases in FOXO1, FOXO4 and NKX2-2 transcription factor gene expression could reflect compensatory responses to brain insulin resistance in this model.

CONCLUSION

Alcohol and tobacco exposures promote ARBD by impairing myelin synthesis, maturation and integrity via distinct but overlapping mechanisms. Public health measures to reduce ARBD should target both alcohol and tobacco abuses.

Regulation of Adult Neurogenesis and Plasticity by (Early) Stress, Glucocorticoids, and Inflammation

Exposure to stress is one of the best-known negative regulators of adult neurogenesis (AN). We discuss changes in neurogenesis in relation to exposure to stress, glucocorticoid hormones, and inflammation, with a particular focus on early development and on lasting effects of stress. Although the effects of acute and mild stress on AN are generally brief and can be quickly overcome, chronic exposure or more severe forms of stress can induce longer lasting reductions in neurogenesis that can, however, in part, be overcome by subsequent exposure to exercise, drugs targeting the stress system, and some antidepressants. Exposure to stress, particularly during the sensitive period of early life, may (re)program brain plasticity, in particular, in the hippocampus. This may increase the risk to develop cognitive or anxiety symptoms, common to brain diseases like dementia and depression in which plasticity changes occur, and a normalization of neurogenesis may be required for a successful treatment response and recovery.

Hippocampal neuron populations are reduced in vervet monkeys with fetal alcohol exposure

Prenatal exposure to beverage alcohol is a major cause of mild mental retardation and developmental delay. In nonendangered alcohol-preferring vervet monkeys, we modeled the most common nondysmorphic form of fetal alcohol syndrome disorder with voluntary drinking during the third trimester of pregnancy. Here, we report significant numerical reductions in the principal hippocampal neurons of fetal alcohol-exposed (FAE) offspring, as compared to age-matched, similarly housed conspecifics with isocaloric sucrose exposure. These deficits, particularly marked in CA1 and CA3, are present neonatally and persist through infancy (5 months) and juvenile (2 years) stages. Although the volumes of hippocampal subdivisions in FAE animals are not atypical at birth, by age 2, they are only 65-70% of those estimated in age-matched controls. These data suggest that moderate, naturalistic alcohol consumption during late pregnancy results in a stable loss of hippocampal neurons and a progressive reduction of hippocampal volume.

Protective effects of resveratrol on the inhibition of hippocampal neurogenesis induced by ethanol during early postnatal life

Ethanol (EtOH) exposure during early postnatal life triggers obvious neurotoxic effects on the developing hippocampus and results in long-term effects on hippocampal neurogenesis. Resveratrol (RSV) has been demonstrated to exert potential neuroprotective effects by promoting hippocampal neurogenesis. However, the effects of RSV on the EtOH-mediated impairment of hippocampal neurogenesis remain undetermined. Thus, mice were pretreated with RSV and were later exposed to EtOH to evaluate its protective effects on EtOH-mediated toxicity during hippocampal development. The results indicated that a brief exposure of EtOH on postnatal day 7 resulted in a significant impairment in hippocampal neurogenesis and a depletion of hippocampal neural precursor cells (NPCs). This effect was attenuated by pretreatment with RSV. Furthermore, EtOH exposure resulted in a reduction in spine density on the granular neurons of the dentate gyrus (DG), and the spines exhibited a less mature morphological phenotype characterized by a higher proportion of stubby spines and a lower proportion of mushroom spines. However, RSV treatment effectively reversed these responses. We further confirmed that RSV treatment reversed the EtOH-induced down-regulation of hippocampal pERK and Hes1 protein levels, which may be related to the proliferation and maintenance of NPCs. Furthermore, EtOH exposure in the C17.2 NPCs also diminished cell proliferation and activated apoptosis, which could be reversed by pretreatment of RSV. Overall, our results suggest that RSV pretreatment protects against EtOH-induced defects in neurogenesis in postnatal mice and may thus play a critical role in preventing EtOH-mediated toxicity in the developing hippocampus.

Transcriptomic study of mouse embryonic neural stem cell differentiation under ethanol treatment

Neural stem cells (NSCs) can be differentiated into one of three cell lineages: neurons, astrocytes or, oligodendrocytes. Some neurotoxins have the ability to deregulate this dynamic process. NSC cell fate can be altered by ethanol as reported previously. Our aim was to investigate the alteration of genes by ethanol during NSC differentiation and to explore the molecular mechanism underlying this phenomenon. Here, mouse fetal forebrain derived NSCs were differentiated for 2 days with or without of ethanol (50 mM). We performed a comparative microarray analysis at day two using GeneChip(®) Mouse Genome 430A 2.0 arrays. Microarray analysis showed that the expressions of 496 genes were altered by ethanol (56 and 440 were up- and down-regulated, respectively). Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed the association of the following altered genes in the Wnt signaling pathway: Wnt5a, Csnk2a1, Tcf7l2, Ccnd2, Nlk, Tbl1x, Tbl1xr1, Rac2 and Nfatc3. Quantitative real time PCR analysis also demonstrated the relative expression levels of these genes. As Wnt signaling is a player of brain development, ethanol-induced alterations may contribute to improper development of the brain. Our data could be a useful resource for elucidating the mechanism behind the ethanol neurotoxicity in developing brain.

Inhibitory Effects of Bisphenol-A on Neural Stem Cells Proliferation and Differentiation in the Rat Brain Are Dependent on Wnt/β-Catenin Pathway

Neurogenesis, a process of generation of new neurons, occurs throughout the life in the hippocampus and sub-ventricular zone (SVZ). Bisphenol-A (BPA), an endocrine disrupter used as surface coating for packaged food cans, injures the developing and adult brain. However, the effects of BPA on neurogenesis and underlying cellular and molecular mechanism(s) are still unknown. Herein, we studied the effect(s) of prenatal and early postnatal exposure of low dose BPA on Wnt/β-catenin signaling pathway that controls different steps of neurogenesis such as neural stem cell (NSC) proliferation and neuronal differentiation. Pregnant rats were treated with 4, 40, and 400 μg BPA/kg body weight orally daily from gestational day 6 to postnatal day 21. Both in vivo and in vitro studies showed that BPA alters NSC proliferation and differentiation. BPA impaired NSC proliferation (5'-bromo-2'-deoxyuridine (BrdU(+)) and nestin(+) cells) and neuronal differentiation (BrdU/doublecortin(+) and BrdU/neuronal nuclei (NeuN(+)) cells) in the hippocampus and SVZ as compared to control. It significantly altered expression/protein levels of neurogenic genes and the Wnt pathway genes in the hippocampus. BPA reduced cellular β-catenin and p-GSK-3β levels and decreased β-catenin nuclear translocation, and cyclin-D1 and TCF/LEF promoter luciferase activity. Specific activation and blockage of the Wnt pathway suggested involvement of this pathway in BPA-mediated inhibition of neurogenesis. Further, blockage of GSK-3β activity by SB415286 and GSK-3β small interfering RNA (siRNA) attenuated BPA-induced downregulation of neurogenesis. Overall, these results suggest significant inhibitory effects of BPA on NSC proliferation and differentiation in the rat via the Wnt/β-catenin signaling pathway.

Downregulation of transketolase activity is related to inhibition of hippocampal progenitor cell proliferation induced by thiamine deficiency

In animal experiments, hippocampal neurogenesis and the activity of thiamine-dependent transketolase decrease markedly under conditions of thiamine deficiency. To further investigate the effect of thiamine deficiency on the proliferation of hippocampal progenitor cells (HPCs) and the potential mechanisms involved in this effect, we cultured HPCs in vitro in the absence of thiamine and found that proliferation and transketolase activity were both significantly repressed. Furthermore, specific inhibition of transketolase activity by oxythiamine strongly inhibited HPC proliferation in a dose-dependent manner. However, thiamine deficiency itself inhibited the proliferation to a greater degree than did oxythiamine. Taken together, our results suggest that modulation of transketolase activity might be one of the mechanisms by which thiamine regulates the proliferation of hippocampal progenitor cells.

Examination of age-dependent effects of fetal ethanol exposure on behavior, hippocampal cell counts, and doublecortin immunoreactivity in rats

Ethanol is known as a potent teratogen having adverse effects on brain and behavior. However, some of the behavioral deficits caused by fetal alcohol exposure and well expressed in juveniles ameliorate with maturation may suggest some kind of functional recovery occurring during postnatal development. The aim of this study was to reexamine age-dependent behavioral impairments in fetal-alcohol rats and to investigate the changes in neurogenesis and gross morphology of the hippocampus during a protracted postnatal period searching for developmental deficits and/or delays that would correlate with behavioral impairments in juveniles and for potential compensatory processes responsible for their amelioration in adults. Ethanol was delivered to the pregnant dams by intragastric intubation throughout 7-21 gestation days at daily dose of 6 g/kg. Isocaloric intubation and intact control groups were included. Locomotor activity, anxiety, and spatial learning tasks were applied to juvenile and young-adult rats from all groups. Unbiased stereological estimates of hippocampal volumes, the total number of pyramidal and granular cells, and double cortin expressing neurons were carried out for postnatal days (PDs) PD1, PD10, PD30, and PD60. Alcohol insult during second trimester equivalent caused significant deficits in the spatial learning in juvenile rats; however, its effect on hippocampal morphology was limited to a marginally lower number of granular cells in dentate gyrus (DG) on PD30. Thus, initial behavioral deficits and the following functional recovery in fetal-alcohol subjects may be due to more subtle plastic changes within the hippocampal formation but also in other structures of the extended hippocampal circuit. Further investigation is required.

Spatial cognition and sexually dimorphic synaptic plasticity balance impairment in rats with chronic prenatal ethanol exposure

Prenatal ethanol exposure can lead to long-lasting impairments in the ability of rats to process spatial information, as well as produce long-lasting deficits in long-term potentiation (LTP), a biological model of learning and memory processing. The present study aimed to examine the sexually dimorphic effects of chronic prenatal ethanol exposure (CPEE) on behavior cognition and synaptic plasticity balance (SPB), and tried to understand a possible mechanism by evaluating the alternation of SPB. The animal model was produced by ethanol exposure throughout gestational period with 4 g/kg bodyweight. Offspring of both male and female were selected and studied on postnatal days 36. Subsequently, the data showed that chronic ethanol exposure resulted in birth weight reduction, losing bodyweight gain, microcephaly and hippocampus weight retardation. In Morris water maze (MWM) test, escape latencies were significantly higher in CPEE-treated rats than that in control ones. They also spent much less time in the target quadrant compared to that of control animals in the probe phase. In addition, it was found that there was a more severe impairment in females than that in males after CPEE treatment. Electrophysiological studies showed that CPEE considerably inhibited hippocampal LTP and facilitated depotentiation in males, while significantly enhanced LTP and suppressed depotentiation in females. A novel index, developed by us, showed that the action of CPEE on SPB was more sensitive in females than that in males, suggesting that it might be an effective index to distinguish the difference of SPB impairment between males and females.

Alcohol consumption negates estrogen-mediated myocardial repair in ovariectomized mice by inhibiting endothelial progenitor cell mobilization and function

We have shown previously that estrogen (estradiol, E2) supplementation enhances voluntary alcohol consumption in ovariectomized female rodents and that increased alcohol consumption impairs ischemic hind limb vascular repair. However, the effect of E2-induced alcohol consumption on post-infarct myocardial repair and on the phenotypic/functional properties of endothelial progenitor cells (EPCs) is not known. Additionally, the molecular signaling of alcohol-estrogen interactions remains to be elucidated. This study examined the effect of E2-induced increases in ethanol consumption on post-infarct myocardial function/repair. Ovariectomized female mice, implanted with 17β-E2 or placebo pellets were given access to alcohol for 6 weeks and subjected to acute myocardial infarction. Left ventricular functions were consistently depressed in mice consuming ethanol compared with those receiving only E2. Alcohol-consuming mice also displayed significantly increased infarct size and reduced capillary density. Ethanol consumption also reduced E2-induced mobilization and homing of EPCs to injured myocardium compared with the E2-alone group. In vitro, exposure of EPCs to ethanol suppressed E2-induced proliferation, survival, and migration and markedly altered E2-induced estrogen receptor-dependent cell survival signaling and gene expression. Furthermore, ethanol-mediated suppression of EPC biology was endothelial nitric oxide synthase-dependent because endothelial nitric oxide synthase-null mice displayed an exaggerated response to post-acute myocardial infarction left ventricular functions. These data suggest that E2 modulation of alcohol consumption, and the ensuing EPC dysfunction, may negatively compete with the beneficial effects of estrogen on post-infarct myocardial repair.

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.

Stem cell therapy: social recognition recovery in a FASD model

To better understand the cellular pathogenetic mechanisms of fetal alcohol spectrum disorder (FASD) and the therapeutic benefit of stem cell treatment, we exposed pregnant rats to ethanol followed by intravenous administration of neural stem cells (NSCs) complexed with atelocollagen to the new born rats and studied recovery of GABAergic interneuron numbers and synaptic protein density in the anterior cingulate cortex, hippocampus and amygdala. Prenatal ethanol exposure reduced both parvalbumin-positive phenotype of GABAergic interneurons and postsynaptic density protein 95 levels in these areas. Intravenous NSC treatment reversed these reductions. Furthermore, treatment with NSCs reversed impaired memory/cognitive function and social interaction behavior. These experiments underscore an important role for synaptic remodeling and GABAergic interneuron genesis in the pathophysiology and treatment of FASD and highlight the therapeutic potential for intravenous NSC administration in FASD utilizing atelocollagen.

Sustained Impairments in Brain Insulin/IGF Signaling in Adolescent Rats Subjected to Binge Alcohol Exposures during Development

Background

Chronic or binge ethanol exposures during development can cause fetal alcohol spectrum disorder (FASD) which consists of an array of neurobehavioral deficits, together with structural, molecular, biochemical, and neurotransmitter abnormalities in the brain. Previous studies showed that perinatal neurodevelopmental defects in FASD are associated with inhibition of brain insulin and insulin-like growth factor (IGF) signaling. However, it is not known whether sustained abnormalities in adolescent brain structure and function are mediated by the same phenomena.

Aims

Using an early postnatal (3^rd trimester equivalent) binge ethanol exposure model, we assessed neurobehavioral function, structure, and the integrity of insulin/IGF signaling in young adolescent cerebella.

Methods

Long Evans male rats were treated with 50 µl of saline (vehicle) or 2 mg/kg of ethanol by i.p. injection on postnatal days (P) 2, 4, 6, and 8. On P19–20, rats were subjected to rotarod testing of motor function, and on P30, they were sacrificed to harvest cerebella for histological, molecular, and biochemical studies.

Results

Binge ethanol exposures impaired motor function, caused sustained cerebellar hypocellularity, and reduced neuronal and oligodendrocyte gene expression. These effects were associated with significant deficits in insulin and IGF signaling, including impaired receptor binding, reduced Akt, and increased GSK-3β activation.

Conclusions

FASD-associated neurobehavioral, structural, and functional abnormalities in young adolescent brains may be mediated by sustained inhibition of insulin/IGF-1 signaling needed for cell survival, neuronal plasticity, and myelin maintenance.

Ethanol affects differentiation-related pathways and suppresses Wnt signaling protein expression in human neural stem cells

BACKGROUND

Prenatal exposure of the fetus to ethanol (EtOH) can be teratogenic. We previously showed that EtOH alters the cell fate of human neural stem cells (NSC). As Wnt signaling plays an important role in fetal brain development, we hypothesized that EtOH suppresses Wnt signaling protein expression in differentiating NSC and thereby contributes to fetal alcohol spectrum disorder.

METHODS

NSC isolated from fetal human brains were cultured in mitogenic media to induce neurospheres, which were dissociated into single-cell suspensions and used for all experiments. Equal numbers of NSC were cultured on lysine/laminin-coated plates for 96 hours in differentiating media containing 0, 20, or 100 mM EtOH. Total mRNA was isolated from samples containing 0 or 100 mM EtOH and changes in expression of 263 genes associated with neurogenesis and NSC differentiation were determined by Oligo GEArray technology. The biological impact of gene changes was estimated using a systems biology approach with pathway express software and KEGG database. Based on the pathways identified, expression of Wnt proteins (Wnt3a and Wnt5a), Wnt-receptor complex proteins (p-LRP6, LRP6, DVL2, and DVL3), Wnt antagonist Naked-2 (NKD-2), and downstream Wnt proteins (β-catenin, Tyr-p-GSK3β, Ser-p-GSK3β) were analyzed by Western blot.

RESULTS

Of the 263 genes examined, the expressions of 22 genes in differentiating NSC were either upwardly or downwardly affected by EtOH. These genes are associated with 5 pathways/cellular processes: axon guidance; hedgehog signaling; TGF-β signaling; cell adhesion molecules; and Wnt signaling. When compared to controls, EtOH, at both 20 and 100 mM concentrations, suppressed the expression of Wnt3a and Wnt5a, receptor complex proteins p-LRP6, LRP6 and DVL2, and cytoplasmic proteins Ser-p-GSK3β and β-catenin. Expression of NKD-2 and DVL3 remained unchanged and the expression of active Tyr-p-GSK3β increased significantly.

CONCLUSIONS

EtOH can significantly alter neural differentiation pathway-related gene expression and suppress Wnt signaling proteins in differentiating human NSC.

Neonatal alcohol exposure disrupts hippocampal neurogenesis and contextual fear conditioning in adult rats

Developmental alcohol exposure can permanently alter brain structures and produce functional impairments in many aspects of behavior, including learning and memory. This study evaluates the effect of neonatal alcohol exposure on adult neurogenesis in the dentate gyrus of the hippocampus and the implications of such exposure for hippocampus-dependent contextual fear conditioning. Alcohol-exposed rats (AE) received 5.25g/kg/day of alcohol on postnatal days (PD) 4-9 (third trimester in humans), in a binge-like manner. Two control groups were included: sham-intubated (SI) and suckle-control (SC). Animals were housed in social cages (3/cage) after weaning. On PD80, animals were injected with 200mg/kg BrdU. Half of the animals were sacrificed 2h later. The remainder were sacrificed on PD114 to evaluate cell survival; separate AE, SI, and SC rats not injected with BrdU were tested for the context preexposure facilitation effect (CPFE; ~PD117). There was no difference in the number of BrdU+ cells in AE, SI and SC groups on PD80. On PD114, cell survival was significantly decreased in AE rats, demonstrating that developmental alcohol exposure damages new cells' ability to incorporate into the network and survive. Behaviorally tested SC and SI groups preexposed to the training context 24h prior to receiving a 1.5mA 2s footshock froze significantly more during the context test than their counterparts preexposed to an alternate context. AE rats failed to show the CPFE. The current study shows the detrimental, long-lasting effects of developmental alcohol exposure on hippocampal adult neurogenesis and contextual fear conditioning.

Altered adult hippocampal neuronal maturation in a rat model of fetal alcohol syndrome

Exposure to ethanol during pregnancy can be devastating to the developing nervous system, leading to significant central nervous system dysfunction. The hippocampus, one of the two brain regions where neurogenesis persists into adulthood, is particularly sensitive to the teratogenic effects of ethanol. In the present study, we tested a rat model of fetal alcohol syndrome (FAS) with ethanol administered via gavage throughout all three trimester equivalents. Subsequently, we assessed cell proliferation, as well as neuronal survival, and differentiation in the dentate gyrus of the hippocampus of adolescent (35 days old), young adult (60 days old) and adult (90 days old) Sprague-Dawley rats. Using both extrinsic (bromodeoxyuridine) and intrinsic (Ki-67) markers, we observed no significant alterations in cell proliferation and survival in ethanol-exposed animals when compared with their pair-fed and ad libitum controls. However, we detected a significant increase in the number of new immature neurons in animals that were exposed to ethanol throughout all three trimester equivalents. This result might reflect a compensatory mechanism to counteract the deleterious effects of prenatal ethanol exposure or an ethanol-induced arrest of the neurogenic process at the early neuronal maturation stages. Taken together these results indicate that exposure to ethanol during the period of brain development causes a long-lasting dysregulation of the neurogenic process, a mechanism that might contribute, at least in part, to the hippocampal deficits that have been reported in rodent models of FAS.

Calcium-mediated repression of β-catenin and its transcriptional signaling mediates neural crest cell death in an avian model of fetal alcohol syndrome

Fetal alcohol syndrome (FAS) is a common birth defect in many societies. Affected individuals have neurodevelopmental disabilities and a distinctive craniofacial dysmorphology. These latter deficits originate during early development from the ethanol-mediated apoptotic depletion of cranial facial progenitors, a population known as the neural crest. We showed previously that this apoptosis is caused because acute ethanol exposure activates G-protein-dependent intracellular calcium within cranial neural crest progenitors, and this calcium transient initiates the cell death. The dysregulated signals that reside downstream of ethanol's calcium transient and effect neural crest death are unknown. Here we show that ethanol's repression of the transcriptional effector β-catenin causes the neural crest losses. Clinically relevant ethanol concentrations (22-78 mM) rapidly deplete nuclear β-catenin from neural crest progenitors, with accompanying losses of β-catenin transcriptional activity and downstream genes that govern neural crest induction, expansion, and survival. Using forced expression studies, we show that β-catenin loss of function (via dominant-negative T cell transcription factor [TCF]) recapitulates ethanol's effects on neural crest apoptosis, whereas β-catenin gain-of-function in ethanol's presence preserves neural crest survival. Blockade of ethanol's calcium transient using Bapta-AM normalizes β-catenin activity and prevents the neural crest losses, whereas ionomycin treatment is sufficient to destabilize β-catenin. We propose that ethanol's repression of β-catenin causes the neural crest losses in this model of FAS. β-Catenin is a novel target for ethanol's teratogenicity. β-Catenin/Wnt signals participate in many developmental events and its rapid and persistent dysregulation by ethanol may explain why the latter is such a potent teratogen.

Voluntary exercise induces adult hippocampal neurogenesis and BDNF expression in a rodent model of fetal alcohol spectrum disorders

Alcohol consumption during pregnancy can result in a myriad of health problems in the affected offspring ranging from growth deficiencies to central nervous system impairments that result in cognitive deficits. Adult hippocampal neurogenesis is thought to play a role in cognition (i.e. learning and memory) and can be modulated by extrinsic factors such as alcohol consumption and physical exercise. We examined the impact of voluntary physical exercise on adult hippocampal neurogenesis in a rat model of fetal alcohol spectrum disorders (FASD). Intragastric intubation was used to deliver ethanol to rats in a highly controlled fashion through all three trimester equivalents (i.e. throughout gestation and during the first 10 days of postnatal life). Ethanol-exposed animals and their pair-fed and ad libitum controls were left undisturbed until they reached a young adult stage at which point they had free access to a running wheel for 12 days. Prenatal and early postnatal ethanol exposure altered cell proliferation in young adult female rats and increased early neuronal maturation without affecting cell survival in the dentate gyrus (DG) of the hippocampus. Voluntary wheel running increased cell proliferation, neuronal maturation and cell survival as well as levels of brain-derived neurotrophic factor in the DG of both ethanol-exposed female rats and their pair-fed and ad libitum controls. These results indicate that the capacity of the brain to respond to exercise is not impaired in this model of FASD, highlighting the potential therapeutic value of physical exercise for this developmental disorder.

The associations between early alcohol use and suicide attempts among adolescents with a history of major depression

OBJECTIVE

Previous studies have identified significant associations between alcohol initiation before the age of 13 years and risk for suicide attempts. However, these associations have not been extensively tested using data obtained from populations with clinically significant psychopathology. The current study seeks to extend knowledge of the associations between early alcohol initiation and risk for suicide by identifying the associations between age of first alcohol use and suicide attempts among a sample of youth age 13 to 15 years with a history of major depression.

METHODOLOGY

Data were obtained from the National Study of Drug Use and Health (NSDUH), a household-based survey of U.S. adolescents and adults age 12 years and older.

RESULTS

Results from these analyses confirm previous reports of significant associations between age of first alcohol use and suicide attempts and extend previous understanding of risk by using data obtained from a household-based survey and from adolescents with clinically relevant psychopathology.

CONCLUSIONS

These findings provide further support for the implementation, enforcement, and continued support of both targeted and universal prevention strategies designed to reduce underage drinking.

Moderate fetal alcohol exposure impairs neurogenic capacity of murine neural stem cells isolated from the adult subventricular zone

Gestational alcohol exposure leads to a spectrum of neurological symptoms which range from severe mental retardation caused by high dose exposure, to subtle cognitive and neuropsychiatric symptoms caused by low-to-moderate doses. We and other investigators have demonstrated that exposure to moderate levels of alcohol throughout gestation leads to impaired neurogenesis in the adult hippocampus, although the mechanisms by which this occurs are not known. To begin to distinguish cell-intrinsic from microenvironmental contributions to impaired adult neurogenesis, we isolated neural stem progenitor cells (NSPCs) from the adult SVZ of mice exposed to moderate levels of alcohol throughout gestation. We found that NSPCs isolated from fetal alcohol exposed (FAE) mice displayed reduced neurosphere formation in culture, as assessed by a serial passage neurosphere assay, and reduced neuronal differentiation upon growth factor withdrawal. These studies suggest that gestational alcohol exposure leads to long-lasting NSPC-intrinsic dysregulation, which may underlie in vivo neurogenic deficits.

Prenatal alcohol exposure reduces the proportion of newly produced neurons and glia in the dentate gyrus of the hippocampus in female rats

Prenatal alcohol exposure (PAE) alters adult neurogenesis and the neurogenic response to stress in male rats. As the effects of stress on neurogenesis are sexually dimorphic, the present study investigated the effects of PAE on adult hippocampal neurogenesis under both nonstressed and stressed conditions in female rats. Pregnant females were assigned to one of three prenatal treatments: (1) alcohol (PAE)-liquid alcohol (ethanol) diet ad libitum (36% ethanol-derived calories); (2) pair-fed-isocaloric liquid diet, with maltose-dextrin substituted for ethanol, in the amount consumed by a PAE partner (g/kg body wt/day of gestation); and (3) control-lab chow ad libitum. Female offspring were assigned to either nonstressed (undisturbed) or stressed (repeated restraint stress for 9 days) conditions. On day 10, all rats were injected with bromodeoxyuridine (BrdU) and perfused either 24 hours (cell proliferation) or 3 weeks (cell survival) later. We found that PAE did not significantly alter cell proliferation or survival, whereas females from the pair-fed condition exhibited elevated levels of cell survival compared to control females. Importantly, however, the proportion of both new neurons and new glial cells in the hippocampal dentate gyrus was reduced in PAE compared to control females. Exposure to stress did not alter neurogenesis in any of the prenatal treatment groups. In summary, compared to females from the control condition, prenatal dietary restriction enhanced the survival of new neurons, whereas PAE altered the differentiation of newly produced cells in the adult dentate gyrus. Alterations in hippocampal neurogenesis following PAE may contribute to learning and memory deficits seen in individuals with fetal alcohol spectrum disorders.

Ethanol-induced small heat shock protein genes in the differentiation of mouse embryonic neural stem cells

Neural stem cells (NSCs) of the neuroepithelium differentiate into one of three central nervous system (CNS) cell lineages: neurons, astrocytes, or oligodendrocytes. In this study, the differentiation potential of NSCs from the forebrain of embryonic day 15 (E15) mouse embryos was analyzed using immunocytochemistry. NSCs were differentiated early in the presence or absence of ethanol (50 mM), and gene expression patterns among NSCs, differentiated cells and ethanol-treated differentiated cells were assessed by microarray and real-time PCR analysis. Genes that were up-regulated in differentiated cells both in the presence and in the absence of ethanol when compared to NSCs were related to the Wnt signaling pathway, including Ctnna1, Wnt5a, Wnt5b, Wnt7a, Fzd3, and Fzd2; genes related to cell adhesion, including Cadm1, Ncam1, and Ncam2; and genes encoding small heat shock proteins, including HspB2, HspB7, and HspB8. In particular, the expression levels of HspB2 and HspB7 were elevated in ethanol-treated differentiated cells compared to non-treated differentiated cells. The gene expression patterns of various heat shock transcription factors (HSFs), proteins that regulate the transcription of heat shock genes, were also analyzed. The expression levels of HSF2 and HSF5 increased in differentiated cells in the presence and absence of ethanol when compared to NSCs. Of these two genes, HSF5 demonstrated an enhanced up-regulation, particularly in ethanol-treated differentiated cells compared to cells that were differentiated in the absence of ethanol. These results imply that HspB2 and HspB7, which are small heat shock proteins with tissue-restricted expression profiles, might be up-regulated by ethanol during the short-term differentiation of NSCs.

Hippocampal cell loss and neurogenesis after fetal alcohol exposure: insights from different rodent models

Prenatal ethanol exposure is invariably detrimental to the developing central nervous system and the hippocampus is particularly sensitive to the teratogenic effects of ethanol. Prenatal ethanol exposure has been shown to result in hippocampal cell loss, altered neuronal morphology and impaired performance on hippocampal-dependent learning and memory tasks in rodents. The dentate gyrus (DG) of the hippocampus is one of the few brain regions where neurogenesis continues into adulthood. This process appears to have functional significance and these newly generated neurons are believed to play important functions in learning and memory. Recently, several groups have shown that adult hippocampal neurogenesis is compromised in animal models of fetal alcohol spectrum disorders (FASD). The direction and magnitude of any changes in neurogenesis, however, appear to depend on a variety of factors that include: the rodent model used; the blood alcohol concentration achieved; the developmental time point when alcohol was administered; and the frequency of ethanol exposure. In this review we will provide an overview of the different rodent models of FASD that are commonly used in this research, emphasizing each of their strengths and limitations. We will also present an up-to-date summary on the effects of prenatal/neonatal ethanol exposure on adult hippocampal neurogenesis and cell loss, highlighting some of the possible molecular mechanisms that might be involved.

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.