How does alcohol impair neuronal migration?

Embryonic ethanol exposure induces ectopic Hcrt and MCH neurons outside hypothalamus in rats and zebrafish: Role in ethanol-induced behavioural disturbances

Embryonic exposure to ethanol increases the risk for alcohol use disorder in humans and stimulates alcohol-related behaviours in different animal models. Evidence in rats and zebrafish suggests that this phenomenon induced by ethanol at low-moderate concentrations involves a stimulatory effect on neurogenesis and density of hypothalamic neurons expressing the peptides, hypocretin/orexin (Hcrt) and melanin-concentrating hormone (MCH), known to promote alcohol consumption. Building on our report in zebrafish showing that ethanol induces ectopic expression of Hcrt neurons outside the hypothalamus, we investigated here whether embryonic ethanol exposure also induces ectopic peptide neurons in rats similar to zebrafish and affects their morphological characteristics and if these ectopic neurons are functional and have a role in the ethanol-induced disturbances in behaviour. We demonstrate in rats that ethanol at a low-moderate dose, in addition to increasing Hcrt and MCH neurons in the lateral hypothalamus where they are normally concentrated, induces ectopic expression of these peptide neurons further anterior in the nucleus accumbens core and ventromedial caudate putamen where they have not been previously observed and causes morphological changes relative to normally located hypothalamic neurons. Similar to rats, embryonic ethanol exposure at a low-moderate dose in zebrafish induces ectopic Hcrt neurons anterior to the hypothalamus and alters their morphology. Notably, laser ablation of these ectopic Hcrt neurons blocks the behavioural effects induced by ethanol exposure, including increased anxiety and locomotor activity. These findings suggest that the ectopic peptide neurons are functional and contribute to the ethanol-induced behavioural disturbances related to the overconsumption of alcohol.

Modeling alcohol-induced neurotoxicity using human induced pluripotent stem cell-derived three-dimensional cerebral organoids

Maternal alcohol exposure during pregnancy can substantially impact the development of the fetus, causing a range of symptoms, known as fetal alcohol spectrum disorders (FASDs), such as cognitive dysfunction and psychiatric disorders, with the pathophysiology and mechanisms largely unknown. Recently developed human cerebral organoids from induced pluripotent stem cells are similar to fetal brains in the aspects of development and structure. These models allow more relevant in vitro systems to be developed for studying FASDs than animal models. Modeling binge drinking using human cerebral organoids, we sought to quantify the downstream toxic effects of alcohol (ethanol) on neural pathology phenotypes and signaling pathways within the organoids. The results revealed that alcohol exposure resulted in unhealthy organoids at cellular, subcellular, bioenergetic metabolism, and gene expression levels. Alcohol induced apoptosis on organoids. The apoptotic effects of alcohol on the organoids depended on the alcohol concentration and varied between cell types. Specifically, neurons were more vulnerable to alcohol-induced apoptosis than astrocytes. The alcohol-treated organoids exhibit ultrastructural changes such as disruption of mitochondria cristae, decreased intensity of mitochondrial matrix, and disorganized cytoskeleton. Alcohol exposure also resulted in mitochondrial dysfunction and metabolic stress in the organoids as evidenced by (1) decreased mitochondrial oxygen consumption rates being linked to basal respiration, ATP production, proton leak, maximal respiration and spare respiratory capacity, and (2) increase of non-mitochondrial respiration in alcohol-treated organoids compared with control groups. Furthermore, we found that alcohol treatment affected the expression of 199 genes out of 17,195 genes analyzed. Bioinformatic analyses showed the association of these dysregulated genes with 37 pathways related to clinically relevant pathologies such as psychiatric disorders, behavior, nervous system development and function, organismal injury and abnormalities, and cellular development. Notably, 187 of these genes are critically involved in neurodevelopment, and/or implicated in nervous system physiology and neurodegeneration. Furthermore, the identified genes are key regulators of multiple pathways linked in networks. This study extends for the first time animal models of binge drinking-related FASDs to a human model, allowing in-depth analyses of neurotoxicity at tissue, cellular, subcellular, metabolism, and gene levels. Hereby, we provide novel insights into alcohol-induced pathologic phenotypes, cell type-specific vulnerability, and affected signaling pathways and molecular networks, that can contribute to a better understanding of the developmental neurotoxic effects of binge drinking during pregnancy.

The Standardization of Diagnostic Criteria for Fetal Alcohol Spectrum Disorder (FASD): Implications for Research, Clinical Practice and Population Health

OBJECTIVE

Fetal Alcohol Spectrum Disorder (FASD) is a preventable disorder caused by maternal alcohol consumption and marked by a range of physical and mental disabilities. Although recognized by the scientific and medical community as a clinical disorder, no internationally standardized diagnostic tool yet exists for FASD.

METHODS AND RESULTS

This review seeks to analyse the discrepancies in existing diagnostic tools for FASD, and the repercussions these differences have on research, public health, and government policy.

CONCLUSIONS

Disagreement on the adoption of a standardised tool is reflective of existing gaps in research on the conditions and factors that influence fetal vulnerability to damage from exposure. This discordance has led to variability in research findings, inconsistencies in government messaging, and misdiagnoses or missed diagnoses. The objective measurement of the timing and level of prenatal alcohol exposure is key to bridging these gaps; however, there is conflicting or limited evidence to support the use of existing measures.

Prenatal carbon monoxide impairs migration of interneurons into the cerebral cortex

Prenatal exposure to carbon monoxide (CO) disrupts brain development, however little is known about effects on neocortical maturation. We exposed pregnant mice to CO from embryonic day 7 (E7) until birth. To study the effect of CO on neuronal migration into the neocortex we injected BrdU during corticogenesis and observed misplaced BrdU+ cells. The majority of cells not in their proper layer colocalized with GAD65/67, suggesting impairment of interneuron migration; interneuron subtypes were also affected. We subsequently followed interneuron migration from E15 organotypic cultures of mouse neocortex exposed to CO; the leading process length of migrating neurons diminished. To examine an underlying mechanism, we assessed the effects of CO on the cellular cascade mediating the cytoskeletal protein vasodilator-stimulated phosphoprotein (VASP). CO exposure resulted in decreased cGMP and in a downstream target, phosphorylated VASP. Organotypic cultures grown in the presence of the phosphodiesterase inhibitor IBMX resulted in a recovery of the leading processes. These data support the idea that CO acts as a signaling molecule and impairs function and neuronal migration by acting through the CO/NO-cGMP pathway. In addition, treated mice demonstrated functional impairment in behavioral tests.

The role of calcium and cyclic nucleotide signaling in cerebellar granule cell migration under normal and pathological conditions

In the developing brain, immature neurons migrate from their sites of origin to their final destination, where they reside for the rest of their lives. This active movement of immature neurons is essential for the formation of normal neuronal cytoarchitecture and proper differentiation. Deficits in migration result in the abnormal development of the brain, leading to a variety of neurological disorders. A myriad of extracellular guidance molecules and intracellular effector molecules is involved in controlling the migration of immature neurons in a cell type, cortical layer and birth-date-specific manner. To date, little is known about how extracellular guidance molecules transfer their information to the intracellular effector molecules, which regulate the migration of immature neurons. In this article, to fill the gap between extracellular guidance molecules and intracellular effector molecules, using the migration of cerebellar granule cells as a model system of neuronal cell migration, we explore the role of second messenger signaling (specifically Ca(2+) and cyclic nucleotide signaling) in the regulation of neuronal cell migration. We will, first, describe the cortical layer-specific changes in granule cell migration. Second, we will discuss the roles of Ca(2+) and cyclic nucleotide signaling in controlling granule cell migration. Third, we will present recent studies showing the roles of Ca(2+) and cyclic nucleotide signaling in the deficits in granule cell migration in mouse models of fetal alcohol spectrum disorders and fetal Minamata disease.

Molecular pathways underpinning ethanol-induced neurodegeneration

While genetics impacts the type and severity of damage following developmental ethanol exposure, little is currently known about the molecular pathways that mediate these effects. Traditionally, research in this area has used a candidate gene approach and evaluated effects on a gene-by-gene basis. Recent studies, however, have begun to use unbiased approaches and genetic reference populations to evaluate the roles of genotype and epigenetic modifications in phenotypic changes following developmental ethanol exposure, similar to studies that evaluated numerous alcohol-related phenotypes in adults. Here, we present work assessing the role of genetics and chromatin-based alterations in mediating ethanol-induced apoptosis in the developing nervous system. Utilizing the expanded family of BXD recombinant inbred mice, animals were exposed to ethanol at postnatal day 7 via subcutaneous injection (5.0 g/kg in 2 doses). Tissue was collected 7 h after the initial ethanol treatment and analyzed by activated caspase-3 immunostaining to visualize dying cells in the cerebral cortex and hippocampus. In parallel, the levels of two histone modifications relevant to apoptosis, γH2AX and H3K14 acetylation, were examined in the cerebral cortex using protein blot analysis. Activated caspase-3 staining identified marked differences in cell death across brain regions between different mouse strains. Genetic analysis of ethanol susceptibility in the hippocampus led to the identification of a quantitative trait locus on chromosome 12, which mediates, at least in part, strain-specific differential vulnerability to ethanol-induced apoptosis. Furthermore, analysis of chromatin modifications in the cerebral cortex revealed a global increase in γH2AX levels following ethanol exposure, but did not show any change in H3K14 acetylation levels. Together, these findings provide new insights into the molecular mechanisms and genetic contributions underlying ethanol-induced neurodegeneration.

Severe gastrooesophageal reflux disease associated with foetal alcohol syndrome

Prenatal alcohol exposure may have adverse effects on the developing foetus resulting in significant growth restriction, characteristic craniofacial features, and central nervous system dysfunction. The toxic effects of alcohol on the developing brain are well recognised. However, little is known about the effects of alcohol on the developing gastrointestinal tract or their mechanism. There are few case reports showing an association between foetal alcohol syndrome and gastrointestinal neuropathy. We report a rare association between foetal alcohol syndrome and severe gastrooesophageal reflux disease in an infant who ultimately required fundoplication to optimise her growth and nutrition. The child had failed to respond to maximal medical treatment (domperidone and omeprazole), high calorie feeds, PEG feeding, or total parenteral nutrition. The effect of alcohol on the developing foetus is not limited to the central nervous system but also can have varied and devastating effects on the gastrointestinal tract.

Preclinical studies of alcohol binge drinking

Binge drinking is prevalent and has serious biomedical consequences. In children, adolescents, and young adults, it is a prominent risk factor for later development of alcohol-use disorders. Many preclinical models have been employed to study the genetic risks for and biomedical consequences of alcohol drinking. However, these models historically did not result in blood-alcohol concentrations (BACs) exceeding 80 mg%; this relatively modest level is the threshold that currently defines a binge session, according to the NIAAA and CDC. Nevertheless, in alcohol-dependent rodents, binge drinking has been well documented. Key neurobiological substrates localized to brain reward and stress systems have been identified. Studies of newer models of binge drinking without dependence are reviewed here. In these models, rodents, non-human primates, and flies will drink enough to reach high BACs. They often display observable signs of intoxication. The neurobiological consequences of these episodes of binge drinking without dependence are reviewed, and preliminary evidence for roles for GABA, glutamate, opioid peptides, and corticotropin releasing factor are discussed, as is the need for more work to identify the antecedents and consequences of binge drinking in both animal models and humans.

Cyanidin-3-glucoside ameliorates ethanol neurotoxicity in the developing brain

Ethanol exposure induces neurodegeneration in the developing central nervous system (CNS). Fetal alcohol spectrum disorders (FASD) are caused by ethanol exposure during pregnancy and are the most common nonhereditary cause of mental retardation. It is important to identify agents that provide neuroprotection against ethanol neurotoxicity. Multiple mechanisms have been proposed for ethanol-induced neurodegeneration, and oxidative stress is one of the most important mechanisms. Recent evidence indicates that glycogen synthase kinase 3β (GSK3β) is a potential mediator of ethanol-mediated neuronal death. Cyanidin-3-glucoside (C3G), a member of the anthocyanin family, is a potent natural antioxidant. Our previous study suggested that C3G inhibited GSK3β activity in neurons. Using a third trimester equivalent mouse model of ethanol exposure, we tested the hypothesis that C3G can ameliorate ethanol-induced neuronal death in the developing brain. Intraperitoneal injection of C3G reduced ethanol-meditated caspase-3 activation, neurodegeneration, and microglial activation in the cerebral cortex of 7-day-old mice. C3G blocked ethanol-mediated GSK3β activation by inducing phosphorylation at serine 9 while reducing the phosphorylation at tyrosine 216. C3G also inhibited ethanol-stimulated expression of malondialdehyde (MDA) and p47phox, indicating that C3G alleviated ethanol-induced oxidative stress. These results provide important insight into the therapeutic potential of C3G.

Alcohol exposure decreases CREB binding protein expression and histone acetylation in the developing cerebellum

Background

Fetal alcohol exposure affects 1 in 100 children making it the leading cause of mental retardation in the US. It has long been known that alcohol affects cerebellum development and function. However, the underlying molecular mechanism is unclear.

Methodology/Principal Findings

We demonstrate that CREB binding protein (CBP) is widely expressed in granule and Purkinje neurons of the developing cerebellar cortex of naïve rats. We also show that exposure to ethanol during the 3^rd trimester-equivalent of human pregnancy reduces CBP levels. CBP is a histone acetyltransferase, a component of the epigenetic mechanism controlling neuronal gene expression. We further demonstrate that the acetylation of both histone H3 and H4 is reduced in the cerebellum of ethanol- treated rats.

Conclusions/Significance

These findings indicate that ethanol exposure decreases the expression and function of CBP in the developing cerebellum. This effect of ethanol may be responsible for the motor coordination deficits that characterize fetal alcohol spectrum disorders.

Ethanol induces endoplasmic reticulum stress in the developing brain

BACKGROUND

Ethanol exposure during brain development causes profound damages to the central nervous system (CNS). The underlying cellular/molecular mechanisms remain unclear. The endoplasmic reticulum (ER) is involved in posttranslational protein processing and transport. The accumulation of unfolded or misfolded proteins in the ER lumen triggers ER stress, which is characterized by translational attenuation, synthesis of ER chaperone proteins, and activation of transcription factors. Sustained ER stress ultimately leads to cell death. ER stress is implicated in various neurodegenerative processes.

METHODS

Using a third trimester equivalent mouse model of ethanol exposure, we tested the hypothesis that ethanol induces ER stress in the developing brain. Seven-day-old C57BL/6 mice were acutely exposed to ethanol by subcutaneous injection and the expression of ER stress-inducible proteins (ERSIPs) and signaling pathways associated with ER stress were examined.

RESULTS

Ethanol exposure significantly increased the expression of ERSIPs and activated signaling pathways associated with ER stress; these include ATF6, CHOP/GADD153, GRP78, and mesencephalic astrocyte-derived neurotrophic factor as well as the phosphorylation of IRE1α, eIF2α, PERK, and PKR. The ethanol-induced increase in ERSIPs occurred within 4 hours of ethanol injection, and levels of some ERSIPs remained elevated after 24 hours of ethanol exposure. Ethanol-induced increase in phosphorylated eIF2α, caspase-12, and CHOP was distributed in neurons of specific areas of the cerebral cortex, hippocampus, and thalamus.

CONCLUSIONS

Our finding indicates that ethanol induces ER stress in immature neurons, providing novel insight into ethanol's detrimental effect on the developing CNS.

Inhibition of cerebellar granule cell turning by alcohol

Ectopic neurons are often found in the brains of fetal alcohol spectrum disorders (FASD) and fetal alcohol syndrome (FAS) patients, suggesting that alcohol exposure impairs neuronal cell migration. Although it has been reported that alcohol decreases the speed of neuronal cell migration, little is known about whether alcohol also affects the turning of neurons. Here we show that ethanol exposure inhibits the turning of cerebellar granule cells in vivo and in vitro. First, in vivo studies using P10 mice demonstrated that a single intraperitoneal injection of ethanol not only reduces the number of turning granule cells but also alters the mode of turning at the EGL-ML border of the cerebellum. Second, in vitro analysis using microexplant cultures of P0-P3 mouse cerebella revealed that ethanol directly reduces the frequency of spontaneous granule cell turning in a dose-dependent manner. Third, the action of ethanol on the frequency of granule cell turning was significantly ameliorated by stimulating Ca(2+) and cGMP signaling or by inhibiting cAMP signaling. Taken together, these results indicate that ethanol affects the frequency and mode of cerebellar granule cell turning through alteration of the Ca(2+) and cyclic nucleotide signaling pathways, suggesting that the abnormal allocation of neurons found in the brains of FASD and FSA patients results, at least in part, from impaired turning of immature neurons by alcohol.

Prenatal and postnatal ethanol experiences modulate consumption of the drug in rat pups, without impairment in the granular cell layer of the main olfactory bulb

The effect of moderate exposure to ethanol during late gestation was studied in terms of its interaction with moderate exposure during nursing from an intoxicated dam. A further issue was whether behavioral effects of ethanol, especially the enhanced ethanol intake known to occur after moderate ethanol prenatally or during nursing, depend upon teratological effects that may include death of neurons in the main olfactory bulb (MOB). During gestational days 17-20 rats were given 0, 1 or 2g/kg ethanol doses intragastrically (i.g.). After parturition these dams were given a dose of 2.5g/kg ethanol i.g. each day and allowed to perform regular nursing activities. During postnatal days (PDs) 15 and 16, ethanol intake of pups was assessed along with aspects of their general activity. In a second experiment pups given the same prenatal treatment as above were tested for blood ethanol concentration (BEC) in response to an ethanol challenge on PD6. A third experiment (Experiment 2b) assessed stereologically the number of cells in the granular cell layer of the MOB on PD7, as a function of analogous pre- and postnatal ethanol exposures. Results revealed that ethanol intake during the third postnatal week was increased by prenatal as well as postnatal ethanol exposure, with a few interesting qualifications. For instance, pups given 1g/kg prenatally did not have increased ethanol intake unless they also had experienced ethanol during nursing. There were no effects of ethanol on either BECs or conventional teratology (cell number). This increases the viability of an explanation of the effects of prenatal and early postnatal ethanol on later ethanol intake in terms of learning and memory.

Ethanol and cognition: indirect effects, neurotoxicity and neuroprotection: a review

Ethanol affects cognition in a number of ways. Indirect effects include intoxication, withdrawal, brain trauma, central nervous system infection, hypoglycemia, hepatic failure, and Marchiafava-Bignami disease. Nutritional deficiency can cause pellagra and Wernicke-Korsakoff disorder. Additionally, ethanol is a direct neurotoxin and in sufficient dosage can cause lasting dementia. However, ethanol also has neuroprotectant properties and in low-to-moderate dosage reduces the risk of dementia, including Alzheimer type. In fetuses ethanol is teratogenic, and whether there exists a safe dose during pregnancy is uncertain and controversial.

Impact of ethanol on the developing GABAergic system

Alcohol intake during pregnancy has a tremendous impact on the developing brain. Embryonic and early postnatal alcohol exposures have been investigated experimentally to elucidate the fetal alcohol spectrum disorders' (FASD) milieu, and new data have emerged to support a devastating effect on the GABAergic system in the adult and developing nervous system. GABA is a predominantly inhibitory neurotransmitter that during development excites neurons and orchestrates several developmental processes such as proliferation, migration, differentiation, and synaptogenesis. This review summarizes and brings new data on neurodevelopmental aspects of the GABAergic system with FASD in experimental telencephalic models.

GSK3beta in ethanol neurotoxicity

Alcohol consumption during pregnancy is a significant public health problem and may result in a wide range of adverse outcomes for the child. The developing central nervous system (CNS) is particularly susceptible to ethanol toxicity. Children with fetal alcohol spectrum disorders (FASD) have a variety of cognitive, behavioral, and neurological impairments. FASD currently represents the leading cause of mental retardation in North America ahead of Down syndrome and cerebral palsy. Ethanol exposure during development causes multiple abnormalities in the brain such as permanent loss of neurons, ectopic neurons, and alterations in synaptogenesis and myelinogenesis. These alcohol-induced structural alterations in the developing brain underlie many of the behavioral deficits observed in FASD. The cellular and molecular mechanisms of ethanol neurotoxicity, however, remain unclear. Ethanol elicits cellular stresses, including oxidative stress and endoplasmic reticulum stress. Glycogen synthase kinase 3beta (GSK3beta), a multifunctional serine/threonine kinase, responds to various cellular stresses. GSK3beta is particularly abundant in the developing CNS, and regulates diverse developmental events in the immature brain, such as neurogenesis and neuronal differentiation, migration, and survival. Available evidence indicates that the activity of GSK3beta in the CNS is affected by ethanol. GSK3beta inhibition provides protection against ethanol neurotoxicity, whereas high GSK3beta activity/expression sensitizes neuronal cells to ethanol-induced damages. It appears that GSK3beta is a converging signaling point that mediates some of ethanol's neurotoxic effects.

Four distinct phases of basket/stellate cell migration after entering their final destination (the molecular layer) in the developing cerebellum

In the adult cerebellum, basket/stellate cells are scattered throughout the ML, but little is known about the process underlying the cell dispersion. To determine the allocation of stellate/basket cells within the ML, we examined their migration in the early postnatal mouse cerebellum. We found that after entering the ML, basket/stellate cells sequentially exhibit four distinct phases of migration. First, the cells migrated radially from the bottom to the top while exhibiting saltatory movement with a single leading process (Phase I). Second, the cells turned at the top and migrated tangentially in a rostro-caudal direction, with an occasional reversal of the direction of migration (Phase II). Third, the cells turned and migrated radially within the ML at a significantly reduced speed while repeatedly extending and withdrawing the leading processes (Phase III). Fourth, the cells turned at the middle and migrated tangentially at their slowest speed, while extending several dendrite-like processes after having completely withdrawn the leading process (Phase IV). Finally, the cells stopped and completed their migration. These results suggest that the dispersion of basket/stellate cells in the ML is controlled by the orchestrated activity of external guidance cues, cell-cell contact and intrinsic programs in a position- and time-dependent manner.

Ethanol inhibition of aspartyl-asparaginyl-beta-hydroxylase in fetal alcohol spectrum disorder: potential link to the impairments in central nervous system neuronal migration

Fetal alcohol spectrum disorder (FASD) is caused by prenatal exposure to alcohol and associated with hypoplasia and impaired neuronal migration in the cerebellum. Neuronal survival and motility are stimulated by insulin and insulin-like growth factor (IGF), whose signaling pathways are major targets of ethanol neurotoxicity. To better understand the mechanisms of ethanol-impaired neuronal migration during development, we examined the effects of chronic gestational exposure to ethanol on aspartyl (asparaginyl)-beta-hydroxylase (AAH) expression, because AAH is regulated by insulin/IGF and mediates neuronal motility. Pregnant Long-Evans rats were pair-fed isocaloric liquid diets containing 0, 8, 18, 26, or 37% ethanol by caloric content from gestation day 6 through delivery. Cerebella harvested from postnatal day 1 pups were used to examine AAH expression in tissue, and neuronal motility in Boyden chamber assays. We also used cerebellar neuron cultures to examine the effects of ethanol on insulin/IGF-stimulated AAH expression, and assess the role of GSK-3beta-mediated phosphorylation on AAH protein levels. Chronic gestational exposure to ethanol caused dose-dependent impairments in neuronal migration and corresponding reductions in AAH protein expression in developing cerebella. In addition, prenatal ethanol exposure inhibited insulin and IGF-I-stimulated directional motility in isolated cerebellar granule neurons. Ethanol-treated neuronal cultures (50mMx96h) also had reduced levels of AAH protein. Mechanistically, we showed that AAH protein could be phosphorylated on Ser residues by GSK-3beta, and that chemical inhibition of GSK-3beta and/or global Caspases increases AAH protein in both control- and ethanol-exposed cells. Ethanol-impaired neuronal migration in FASD is associated with reduced AAH expression. Because ethanol increases the activities of both GSK-3beta and Caspases, the inhibitory effect of ethanol on neuronal migration could be mediated by increased GSK-3beta phosphorylation and Caspase degradation of AAH protein.

Autonomous turning of cerebellar granule cells in vitro by intrinsic programs

External guidance cues play a role in controlling neuronal cell turning in the developing brain, but little is known about whether intrinsic programs are also involved in controlling the turning. In this study, we examined whether granule cells undergo autonomous changes in the direction of migration in the microexplant cultures of the early postnatal mouse cerebellum. We found that granule cells exhibit spontaneous and periodical turning without cell-cell contact and in the absence of external guidance cues. The frequency of turning was increased by stimulating the Ca(2+) influx and the internal Ca(2+) release, or inhibiting the cAMP signaling pathway, while the frequency was reduced by inhibiting the Ca(2+) influx. Granule cell turning in vitro was classified into four distinct modes, which were characterized by the morphological changes in the leading process and the trailing process, such as bifurcating, turning, withdrawing, and changing the polarity. The occurrence of the 1st and 2nd modes of turning was differentially affected by altering the Ca(2+) and cAMP signaling pathways. Collectively, the results demonstrate that intrinsic programs regulate the autonomous turning of cerebellar granule cells in vitro. Furthermore, the results suggest that extrinsic signals play a role as essential modulators of intrinsic programs.

Ethanol exhibits specificity in its effects on differentiation of hematopoietic progenitors

Ethanol is a known teratogen but the mechanisms by which this simple compound affects fetal development remain unresolved. The goal of the current study was to determine the mechanism by which ethanol affects lymphoid differentiation using an in vitro model of ethanol exposure. Primitive hematopoietic oligoclonal-neonatal-progenitor cells (ONP), with the phenotype Lin(-)HSA(lo)CD43(lo)Sca-1(-)c-Kit(+) that are present in neonatal but not adult bone marrow were sorted from the bone marrow of 2-week-old C57BL/6J mice and cultured under conditions that favor either B cell or myeloid cell differentiation with or without addition of ethanol. The overall growth of the ONP cells was not significantly affected by inclusion of up to 100mM ethanol in the culture medium. However, the differentiation of the progenitor cells along the B-cell pathway was significantly impaired by ethanol in a dose-dependent manner. Exposure of ONP cells to 100mM ethanol resulted in greater than 95% inhibition of B cell differentiation. Conversely, ethanol concentrations up to and including 100mM had no significant effect on differentiation along the myeloid pathway. The effect of ethanol on transcription factor expression was consistent with the effects on differentiation. ONP cells grown in 100mM ethanol failed to upregulate Pax5 and EBF, transcriptional regulators that are necessary for B cell development. However, ethanol had no significant effect on the upregulation of PU.1, a transcription factor that, when expressed in high concentration, favors myeloid cell development. Taken together, these results suggest that ethanol has specificity in its effects on differentiation of hematopoietic progenitors.

Insulin-like growth factor-I mitigates motor coordination deficits associated with neonatal alcohol exposure in rats

Prenatal alcohol exposure can affect brain development, leading to behavioral problems, including overactivity, motor dysfunction and learning deficits. Despite warnings about the effects of drinking during pregnancy, rates of fetal alcohol syndrome remain unchanged and thus, there is an urgent need to identify interventions that reduce the severity of alcohol's teratogenic effects. Insulin-like growth factor-I (IGF-I) is neuroprotective against ethanol-related toxicity and promotes white matter production following a number of insults. Given that prenatal alcohol leads to cell death and white matter deficits, the present study examined whether IGF-I could reduce the severity of behavioral deficits associated with developmental alcohol exposure. Sprague-Dawley rat pups received ethanol intubations (5.25 g/kg/day) or sham intubations on postnatal days (PD) 4-9, a period of brain development equivalent to the third trimester. On PD 10-13, subjects from each treatment received 0 or 10 microg IGF-I intranasally each day. Subjects were then tested on a series of behavioral tasks including open field activity (PD 18-21), parallel bar motor coordination (PD 30-32) and Morris maze spatial learning (PD 45-52). Ethanol exposure produced overactivity, motor coordination impairments, and spatial learning deficits. IGF-I treatment significantly mitigated ethanol's effects on motor coordination, but not on the other two behavioral tasks. These data indicate that IGF-I may be a potential treatment for some of ethanol's damaging effects, a finding that has important implications for children of women who drink alcohol during pregnancy.

Ethanol increases fetal human neurosphere size and alters adhesion molecule gene expression

BACKGROUND

Ethanol (ETOH) consumption by pregnant women can result in Fetal Alcohol Spectrum Disorder (FASD). To date, the cellular targets and mechanisms responsible for FASD are not fully characterized. Our aim was to determine if ETOH can affect fetal human brain-derived neural progenitor cells (NPC).

METHODS

Neural progenitor cells were isolated by positive selection from normal second trimester fetal human brains (n = 4) and cultured, for up to 72 hours, in mitogenic media containing 0, 1, 10, or 100 mM ETOH. From 48 to 72 hours in culture, neurospheres generated in these conditions were filmed using time-lapse video microscopy. At the end of 72 hours, neurosphere diameter and roundness were measured using videographic software. Mitotic phase analysis of cell-cycle activity and apoptotic cell count were also performed at this time, by flow cytometry using propidium iodide (PI) staining. Real-time PCR was used to estimate expression of genes associated with cell adhesion pathways.

RESULTS

Neurosphere diameter correlated positively (r = 0.87) with increasing ETOH concentrations. There was no significant difference in cell-cycle activity and no significant increase in apoptosis with increasing ETOH concentrations. Time-lapse video microscopy showed that ETOH (100 mM) reduced the time for neurosphere coalescence. Real-time PCR analysis showed that ETOH significantly altered the expression of genes involved in cell adhesion. There was an increase in the expression of alpha and beta Laminins 1, beta Integrins 3 and 5, Secreted phosphoprotein1 and Sarcoglycan epsilon. No change in the expression of beta Actin was observed while the expression of beta Integrin 2 was significantly suppressed.

CONCLUSIONS

ETOH had no effect on NPC apoptosis but, resulted in more rapid coalescence and increased volume of neurospheres. Additionally, the expression of genes associated with cell adhesion was significantly altered. ETOH induced changes in NPC surface adhesion interactions may underlie aspects of neurodevelopmental abnormalities in FASD.

Effects of chronic alcohol drinking on receptor-binding, internalization, and degradation of human immunodeficiency virus 1 envelope protein gp120 in hepatocytes

Although alcohol drinking increases susceptibility to human immunodeficiency virus (HIV) infection, possible mechanisms underlying the effects of alcohol are not yet known. Since the HIV envelope protein gp120 plays a key role in progression of HIV infection, the aim of the present study was to evaluate the toxicity and degradation of gp120 in hepatocytes isolated from liver of alcohol-preferring rats drinking either 15% ethanol in water or pure water for 70 days. The hypothesis was that alcohol drinking augmented the toxicity, but suppressed degradation of gp120. Hepatocytes from water-drinking rats (C-cells) or ethanol-drinking rats (Et-cells) were treated with laptacystin, anti-CD4 antibodies, CCR5 antagonist, or mannose, followed by [(125)I]gp120 or native gp120. At predetermined intervals, control (C) and ethanol exposed (Et) cells were analyzed for toxicity and degradation of gp120. In C-cells, [(125)I]gp120 binding and internalization peaked within 5-45 min and remained elevated for up to 10h and then decreased gradually. In Et-cells, [(125)I]gp120 binding peaked comparably to C-cells, but the binding remained to the peak level throughout the experimental period. C-cells exhibited the lysosomal/ubiquitin-mediated degradation of intracellular gp120, resulting in released gp120 fragments into the incubation medium that suppressed gp120-CD4 binding, improved cell viability, and inhibited gp120-induced apoptosis. Ethanol drinking suppressed gp120 degradation in and release of gp120 fragments from hepatocytes. The incubation medium of Et-cells did not suppress gp120-CD4 binding or the gp120-mediated apoptosis in hepatocytes. Thus, chronic alcohol drinking augmented the adverse effects of gp120 possibly by suppressing its degradation in hepatocytes. The present observation also suggests that a number of CCR5 or ubiquitin-based therapeutic drugs may not be effective in suppressing HIV infection in alcohol-drinking subjects.

Cerebellar cortical-layer-specific control of neuronal migration by pituitary adenylate cyclase-activating polypeptide

Migration of immature neurons is essential for forming the cortical layers and nuclei. Impairment of migration results in aberrant neuronal cytoarchitecture, which leads to various neurological disorders. Neurons alter the mode, tempo and rate of migration when they translocate through different cortical layers, but little is known about the mechanisms underlying this process. Here we show that endogenous pituitary adenylate cyclase-activating polypeptide (PACAP) has short-term and cortical-layer-specific effects on granule cell migration in the early postnatal mouse cerebellum. Application of exogenous PACAP significantly slowed the migration of isolated granule cells and shortened the leading process in the microexplant cultures of the postnatal day (P)0-3 cerebella. Interestingly, in the cerebellar slices of P10 mice, application of exogenous PACAP significantly inhibited granule cell migration in the external granular layer (EGL) and molecular layer (ML), but failed to alter the movement in the Purkinje cell layer (PCL) and internal granular layer (IGL). In contrast, application of PACAP antagonist accelerated granule cell migration in the PCL, but did not change the movement in the EGL, ML and IGL. Inhibition of the cAMP signaling and the activity of phospholipase C significantly reduced the effects of exogenous PACAP on granule cell migration. The PACAP action on granule cell migration was transient, and lasted for approximately 2 h. The duration of PACAP action on granule cell migration was determined by the desensitization of its receptors and prolonged by inhibiting the protein kinase C. Endogenous PACAP was present sporadically in the bottom of the ML, intensively in the PCL, and throughout the IGL. Collectively, these results indicated that PACAP acts on granule cell migration as "a brake (stop signal) for cell movement." Furthermore, these results suggest that endogenous PACAP slows granule cell migration when the cells enter the PACAP-rich PCL, and 2 h later the desensitization of PACAP receptors allows the cells to accelerate the rate of migration and to actively move within the PACAP-rich IGL. Therefore, endogenous PACAP may provide a cue that regulates granule cell migration in a cerebellar cortical-layer-specific manner.