Alcohol inhibits neurite extension and increases N-myc and c-myc proteins

The structural effects of Vitamin A deficiency on biological macromolecules due to ethanol consumption and withdrawal: An FTIR study with chemometrics

The structural effects of vitamin A-deficiency were examined on the molecular profiles of biomolecules of male rat hippocampus during prolonged ethanol intake/withdrawal using FT-IR spectroscopy coupled with chemometrics. Liquid ethanol diet with/without vitamin A was maintained to adult rats for 3-months. The rats were decapitated at different ethanol withdrawal times and FT-IR spectra were obtained. Ethanol consumption/withdrawal produced significant changes in proteins' conformations, while having insignificant structural effects on lipids. In vitamin A deficiency, ethanol produced structural changes in lipids by lipid ordering especially in the early-ethanol withdrawal. Furthermore, an increase in lipid and protein content, saturated/unsaturated lipid ratio, a decrease in nucleic acids content and decrease in membrane fluidity were observed. These changes were less severe in the presence of Vitamin A. This study is clinically important for individuals with vitamin A deficiency because they have to be more cautious when consuming alcohol to protect themselves from cognitive dysfunctions.

Evaluation of Anti-Biofilm Capability of Cordycepin Against Candida albicans

INTRODUCTION

The opportunistic pathogen Candida albicans can form biofilms, resulting in drug resistance with great risk to medical treatment.

METHODOLOGY

We investigated the ability of C. albicans to form biofilms on different materials, as well as the inhibitory and eradicating effects of cordycepin on biofilm. The action mechanism of cordycepin against biofilm was studied by crystal violet staining, XTT [2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction method, phenol-sulfuric acid method, cellular superficial hydrophobicity (CSH) assay, and confocal laser scanning microscope observation. We also evaluated the acute toxicity of cordycepin in vivo.

RESULTS

The results showed facile formation of biofilms by C. albicans on polypropylene. The 50% minimum inhibitory concentration (MIC50) of cordycepin was 0.062 mg/mL. A concentration of 0.125 mg/mL significantly decreased biofilm formation, metabolic activity, secretion of extracellular polysaccharides, and relative CSH. Cordycepin could inhibit biofilm formation at low concentration without affecting fungal growth. In addition, cordycepin effectively eradicated 59.14% of mature biofilms of C. albicans at a concentration of 0.5 mg/mL. For acute toxicity, the LD50 (50% of lethal dose) of cordycepin was determined as higher than 500 mg/kg for mice.

CONCLUSION

The results of this study show that cordycepin significantly inhibited and eradicated biofilms by decreasing metabolic activity, the ratio of living cells, the hydrophobicity, and damaging the extracellular polysaccharides of biofilm. These findings should facilitate more effective application of cordycepin and suggest a new direction for the treatment of fungal infections.

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 changes in poly (ADP ribose) polymerase and neuronal developmental gene expression

Prenatal alcohol exposure has profound effects on neuronal growth and development. Poly-ADP Ribose Polymerase (PARP) enzymes are perhaps unique in the field of epigenetics in that they directly participate in histone modifications, transcription factor modifications, DNA methylation/demethylation and are highly inducible by ethanol. It was our hypothesis that ethanol would induce PARP enzymatic activity leading to alterations in neurodevelopmental gene expression. Mouse E18 cortical neurons were treated with ethanol, PARP inhibitors, and nuclear hormone receptor transcription factor PPARγ agonists and antagonists. Subsequently, we measured PARP activity and changes in Bdnf, OKSM (Oct4, Klf4, Sox2, c-Myc), DNA methylating/demethylating factors, and Pparγ mRNA expression, promoter 5-methylcytosine (5MC) and 5-hydroxymethylcytosine (5HMC), and PPARγ promoter binding. We found that ethanol reduced Bdnf4, 9a, and Klf4 mRNA expression, and increased c-Myc expression. These changes were reversed with a PARP inhibitor. In agreement with its role in DNA demethylation PARP inhibition increased 5MC levels at the c-Myc promoter. In addition, we found that inhibition of PARP enzymatic activity increased PPARγ promoter binding, and this corresponded to increased Bdnf and Klf4 mRNA expression. Our results suggest that PARP participates in DNA demethylation and reduces PPARγ promoter binding. The current study underscores the importance of PARP in ethanol-induced changes to neurodevelopmental gene expression.

Impairment of insulin receptor substrate 1 signaling by insulin resistance inhibits neurite outgrowth and aggravates neuronal cell death

In the central nervous system (CNS), insulin resistance (I/R) can cause defective neurite outgrowth and neuronal cell death, which can eventually lead to cognitive deficits. Recent research has focused on the relationship between I/R and the cognitive impairment caused by dementia, with the goal of developing treatments for dementia. Insulin signal transduction mediated by insulin receptor substrate (IRS-1) has been thoroughly studied in the CNS of patients with I/R. In the present study, we investigated whether the impairment of IRS-1-mediated insulin signaling contributes to neurite outgrowth and neuronal loss, both in mice fed a high-fat diet and in mouse neuroblastoma (Neuro2A) cells. To investigate the changes caused by the inhibition of IRS-1-mediated insulin signaling in the brain, we performed Cresyl Violet staining and immunochemical analysis. To investigate the changes caused by the inhibition of IRS-1-mediated insulin signaling in neuroblastoma cells, we performed Western blot analysis, reverse transcription-PCR, and immunochemical analysis. We show that the deactivation of IRS-1-mediated insulin signaling can inhibit neuronal outgrowth and aggravate neuronal cell death in the insulin-resistant CNS. Thus, IRS-1-mediated insulin signal transduction may be an important factor in the treatment of cognitive decline induced by I/R.

Ethanol diverts early neuronal differentiation trajectory of embryonic stem cells by disrupting the balance of lineage specifiers

Background

Ethanol is a toxin responsible for the neurodevelopmental deficits of Fetal Alcohol Spectrum Disorders (FASD). Recent evidence suggests that ethanol modulates the protein expression of lineage specifier transcription factors Oct4 (Pou5f1) and Sox2 in early stages of mouse embryonic stem (ES) cell differentiation. We hypothesized that ethanol induced an imbalance in the expression of Oct4 and Sox2 in early differentiation, that dysregulated the expression of associated and target genes and signaling molecules and diverted cells from neuroectodermal (NE) formation.

Methodology/Principal Findings

We showed modulation by ethanol of 33 genes during ES cell differentiation, using high throughput microfluidic dynamic array chips measuring 2,304 real time quantitative PCR assays. Based on the overall gene expression dynamics, ethanol drove cells along a differentiation trajectory away from NE fate. These ethanol-induced gene expression changes were observed as early as within 2 days of differentiation, and were independent of cell proliferation or apoptosis. Gene expression changes were correlated with fewer βIII-tubulin positive cells of an immature neural progenitor phenotype, as well as a disrupted actin cytoskeleton were observed. Moreover, Tuba1a and Gapdh housekeeping genes were modulated by ethanol during differentiation and were replaced by a set of ribosomal genes with stable expression.

Conclusions/Significance

These findings provided an ethanol-response gene signature and pointed to the transcriptional dynamics underlying lineage imbalance that may be relevant to FASD phenotype.

Ethanol impairs muscarinic receptor-induced neuritogenesis in rat hippocampal slices: Role of astrocytes and extracellular matrix proteins

In an in vitro co-culture system of astrocytes and neurons, stimulation of cholinergic muscarinic receptors in astrocytes had been shown to cause neuritogenesis in hippocampal neurons, and this effect was inhibited by ethanol. The present study sought to confirm these earlier findings in a more complex system, in vitro rat hippocampal slices in culture. Exposure of hippocampal slices to the cholinergic agonist carbachol (1mM for 24h) induced neurite outgrowth in hippocampal pyramidal neurons, which was mediated by activation of muscarinic M3 receptors. Specifically, carbachol induced a >4-fold increase in the length of the longest neurite, and a 4-fold increase in the length of minor neurites and in the number of branches. Co-incubation of carbachol with ethanol (50mM) resulted in significant inhibition of the effects induced by carbachol on all parameters measured. Neurite outgrowth in CNS neurons is dependent on various permissive factors that are produced and released by glial cells. In hippocampal slices carbachol increased the levels of two extracellular matrix protein, fibronectin and laminin-1, by 1.6-fold, as measured by Western blot. Co-incubation of carbachol with ethanol significantly inhibited these increases. Carbachol-induced increases in levels of extracellular matrix proteins were antagonized by a M3 muscarinic receptor antagonist. Furthermore, function-blocking fibronectin or laminin-1 antibodies antagonized the effect of carbachol on neurite outgrowth. These results indicate that in hippocampal slices stimulation of muscarinic M3 receptors induces neurite outgrowth, which is mediated by fibronectin and laminin-1, two extracellular matrix proteins released by astrocytes. By decreasing fibronectin and laminin levels ethanol prevents carbachol-induced neuritogenesis. These findings highlight the importance of glial-neuronal interactions as important targets in the developmental neurotoxicity of alcohol.

Ethanol inhibits neuritogenesis induced by astrocyte muscarinic receptors

In utero alcohol exposure can lead to fetal alcohol spectrum disorders, characterized by cognitive and behavioral deficits. In vivo and in vitro studies have shown that ethanol alters neuronal development. We have recently shown that stimulation of M(3) muscarinic receptors in astrocytes increases the synthesis and release of fibronectin, laminin, and plasminogen activator inhibitor-1, causing neurite outgrowth in hippocampal neurons. As M(3) muscarinic receptor signaling in astroglial cells is strongly inhibited by ethanol, we hypothesized that ethanol may also inhibit neuritogenesis in hippocampal neurons induced by carbachol-stimulated astrocytes. In the present study, we report that the effect of carbachol-stimulated astrocytes on hippocampal neuron neurite outgrowth was inhibited in a concentration-dependent manner (25-100 mM) by ethanol. This effect was because of the inhibition of the release of fibronectin, laminin, and plasminogen activator inhibitor-1. Similar effects on neuritogenesis and on the release of astrocyte extracellular proteins were observed after the incubation of astrocytes with carbachol in the presence of 1-butanol, another short-chain alcohol, which like ethanol is a competitive substrate for phospholipase D, but not by tert-butanol, its analog that is not a substrate for this enzyme. This study identifies a potential novel mechanism involved in the developmental effects of ethanol mediated by the interaction of ethanol with cell signaling in astrocytes, leading to an impairment in neuron-astrocyte communication.

Ethanol inhibits muscarinic receptor-induced axonal growth in rat hippocampal neurons

BACKGROUND

In utero alcohol exposure can lead to fetal alcohol spectrum (FAS) disorders characterized by cognitive and behavioral deficits. In vivo and in vitro studies have shown that ethanol alters neuronal development. One mechanism through which ethanol has been shown to exert its effects is the perturbation of activated signaling cascades. The cholinergic agonist carbachol has been shown to induce axonal outgrowth through intracellular calcium mobilization, protein kinase C (PKC) activation, and ERK1/2 phosphorylation. This study investigated the effect of ethanol on the differentiation of rat hippocampal pyramidal neurons induced by carbachol as a possible mechanism involved in the developmental neurotoxicity of ethanol.

METHODS

Prenatal rat hippocampal pyramidal neurons were treated with ethanol (50 to 75 mM) in the presence or absence of carbachol for 24 hours. Neurite outgrowth was assessed spectrophotometrically; axonal length was measured in neurons fixed and immunolabeled with the neuron-specific betaIII tubulin antibody; cytotoxicity was analyzed using the thiazolyl blue tetrazolium bromide assay. The effect of ethanol on carbachol-stimulated intracellular calcium mobilization was assessed utilizing the fluorescent calcium probe, Fluo-3AM. The PepTag(R) assay for nonradioactive detection of PKC from Promega was used to measure PKC activity, and ERK1/2 activation was determined by densitometric analysis of Western blots probed for phospo-ERK1/2.

RESULTS

Ethanol treatment (50 to 75 mM) caused an inhibition of carbachol-induced axonal growth, without affecting neuronal viability. Neuron treatment for 15 minutes with ethanol did not inhibit the carbachol-stimulated rise in intracellular calcium, while inhibiting PKC activity at the highest tested concentration and ERK1/2 phosphorylation at both the concentrations used in this study. On the other hand, neuron treatment for 24 hours with ethanol significantly inhibited carbachol-induced increase in intracellular calcium.

CONCLUSIONS

Ethanol inhibited carbachol-induced neurite outgrowth by inhibiting PKC and ERK1/2 activation. These effects may be, in part, responsible for some of the cognitive deficits associated with in utero alcohol exposure.

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.

Long-term ethanol exposure impairs neuronal differentiation of human neuroblastoma cells involving neurotrophin-mediated intracellular signaling and in particular protein kinase C

BACKGROUND

Revealing the molecular changes in chronic ethanol-impaired neuronal differentiation may be of great importance for understanding ethanol-related pathology in embryonic development but also in the adult brain. In this study, both acute and long-term effects of ethanol on neuronal differentiation of human neuroblastoma cells were investigated. We focused on several aspects of brain-derived neurotrophic factor (BDNF) signaling because BDNF activates the extracellular signal-regulated kinase (ERK) cascade, promoting neuronal differentiation including neurite outgrowth.

METHODS

The effects of ethanol exposure on morphological differentiation, cellular density, neuronal marker proteins, basal ERK activity, and ERK responsiveness to BDNF were measured over 2 to 4 weeks. qRT-PCR and Western blotting were performed to investigate the expression of neurotrophin receptor tyrosin kinase B (TrkB), members of the ERK-cascade, protein kinase C (PKC) isoforms and Raf-Kinase-Inhibitor-Protein (RKIP).

RESULTS

Chronic ethanol interfered with the development of a neuronal network consisting of cell clusters and neuritic bundles. Furthermore, neuronal and synaptic markers were reduced, indicating impaired neuronal differentiation. BDNF-mediated activation of the ERK cascade was found to be continuously impaired by ethanol. This could not be explained by expressional changes monitored for TrkB, Raf-1, MEK, and ERK. However, BDNF also activates PKC signaling which involves RKIP, which finally leads to ERK activation as well. Therefore, we hypothesized that ethanol impairs this branch of BDNF signaling. Indeed, both PKC and RKIP were significantly down-regulated.

CONCLUSIONS

Chronic ethanol exposure impaired neuronal differentiation of neuroblastoma cells and BDNF signaling, particularly the PKC-dependent branch. RKIP, acting as a signaling switch at the merge of the PKC cascade and the Raf/MEK/ERK cascade, was associated with neuronal differentiation and significantly reduced in ethanol treatment. Moreover, PKC expression itself was even more strongly reduced. In contrast, members of the Raf-1/MEK/ERK cascade were less affected and the observed changes were not associated with impaired differentiation. Thus, reduced RKIP and PKC levels and subsequently reduced positive feedback on ERK activation provide an explanation for the striking effects of long-term ethanol exposure on BDNF signal transduction and neuronal differentiation, respectively.

Upregulation of beta-catenin levels in superior frontal cortex of chronic alcoholics

BACKGROUND

Chronic and excessive alcohol misuse results in neuroadaptive changes in the brain. The complex nature of behavioral, psychological, emotional, and neuropathological characteristics associated with alcoholism is likely a reflection of the network of proteins that are affected by alcohol-induced gene expression patterns in specific brain regions. At the molecular level, however, knowledge remains limited regarding alterations in protein expression levels affected by chronic alcohol abuse. Thus, novel techniques that allow a comprehensive assessment of this complexity will enable the simultaneous assessment of changes across a group of proteins in the relevant neural circuitry.

METHODS

A proteomics analysis was performed using antibody microarrays to determine differential protein levels in superior frontal cortices between chronic alcoholics and age- and gender-matched control subjects. Seventeen proteins related to the catenin signaling pathway were analyzed, including alpha-, beta-, and delta-catenins, their upstream activators cadherin-3 (type I cadherin) and cadherin-5 (type II cadherin), and 5 cytoplasmic regulators c-Src, CK1 epsilon, GSK-3beta, PP2A-C alpha, and APC, as well as the nuclear complex partner of beta-catenin CBP and 2 downstream genes Myc and cyclin D1. ILK, G(alpha1), G(beta1), and G(beta2), which are activity regulators of GSK-3beta, were also analyzed.

RESULTS

Both alpha- and beta-catenin showed significantly increased levels, while delta-catenin did not change significantly, in chronic alcoholics. In addition, the level of the beta-catenin downstream gene product Myc was significantly increased. Average levels of the catenin regulators c-Src, CK1 epsilon, and APC were also increased in chronic alcoholics, but the changes were not statistically significant.

CONCLUSION

Chronic and excessive alcohol consumption leads to an upregulation of alpha- and beta-catenin levels, which in turn increase downstream gene expressions such as Myc that is controlled by beta-catenin signaling. This study showed that the beta-catenin signal transduction pathway was upregulated by chronic alcohol abuse, and prompts further investigation of mechanisms underlying the upregulation of alpha- and beta-catenins in alcoholism, which may have considerable pathogenic and therapeutic relevance.

Prenatal-through-postnatal exposure to moderate levels of ethanol leads to damage on the hippocampal CA1 field of juvenile rats

Experimental paradigms conducted to assess the neurotoxic effects of ethanol exposure on hippocampus development have yielded controversial findings. Hippocampal CA1 population and some cytoarchitectural parameters of pyramidal cells were studied after exposure to ethanol during early development, in rats. Examination of 30-day-old offspring of rats exposed to moderate levels of ethanol during gestation through lactation showed an increased volume of the hippocampal CA1 field compared to untreated or pair-fed control pups, as well as a reduced number of pyramidal neurons. In addition, the number of spines from surviving CA1 pyramidal neurons was reduced. Furthermore, stubby and wide spines were proportionally increased, while the proportion of mushroom and ramified spines was reduced; no variation in the proportion of thin spines was observed. Because alcoholic women usually drink alcohol before, during, and after pregnancy, a broad-range experimental model of alcohol exposure was used in this study. The present findings show that experimental exposure to moderate levels of ethanol, resembling the human situation in alcoholic mothers, leads to loss of hippocampal CA1 pyramidal neurons, along with several pathological and plastic events in the dendritic arborization of these neurons. Some ethanol-induced excitotoxicity-related mechanisms, which may be underlying these effects, are discussed.

Ethanol effects on the developing zebrafish: neurobehavior and skeletal morphogenesis

Exposure to ethanol during development can lead to a constellation of congenital anomalies, resulting in prenatal and postnatal failure to thrive, central nervous system (CNS) deficits, and a number of patterning defects that lead to defects in the cardiovascular system, facial structures, and limbs. The cellular, biochemical, and molecular mechanisms by which ethanol exerts its developmental toxicity and the genes that influence sensitivity to developmental ethanol exposure have yet to be discovered, despite being one of the more common nongenetic causes of birth defects. The zebrafish undergoes much the same patterning and morphogenesis as other vertebrate embryos do--including humans--that are distinct and cannot be studied in invertebrates. Developmental processes in zebrafish are affected by ethanol exposure in a dose-dependent manner, resulting in learning and memory deficits, cell death in the CNS, skeletal dysmorphogenesis, and alterations in startle reflex responses. Interestingly, significant ethanol effects on learning and behavioral endpoints occurred at concentrations well below those that induced cell death in the CNS. This work provides the foundation for identifying genes and pathways involved in developmental alcohol toxicity in vertebrates, leading to a more complete mechanistic understanding of fetal alcohol disorders in humans.

Time-lapse analysis of ethanol's effects on axon growth in vitro

The cortical abnormalities found in animal models of fetal alcohol syndrome (FAS) suggest a disruption of axon growth. After emerging from the cell body, axons exhibit saltatory growth, cycling between periods of extension and periods of retraction. The timing of neuronal process outgrowth an the balance between extension and retraction together determine the net rate of axon elongation, and may be independently regulated. In this study, we used time-lapse digital microscopy and custom-designed analytic software to assess the effects of ethanol on the growth of axons from embryonic rat hippocampal pyramidal neurons in culture during 24 h of development, beginning approximately 7 h after plating. We recorded the amount of time elapsed before axons emerged, the relative amount of time spent in periods of growth and nongrowth, and the rate and direction of change in axon length during both periods of growth and nongrowth. The initiation of axonal outgrowth was significantly delayed by ethanol in a dose-dependent fashion at concentrations in the medium at or above 100 mg/dl. However, once established, axons exhibited accelerated growth in the presence of ethanol. This increase in overall growth rate was primarily due to a significant decrease in axon retraction during nongrowth periods. Ethanol did not affect the duration or frequency of growth and nongrowth periods. We propose, therefore, that mechanisms underlying ethanol-mediated changes in axon growth are linked to signaling events that differentially regulate outgrowth and retraction.

Nuclear transcription factors in the hippocampus

In the mammalian hippocampus, there is a trisynaptic loop that has been often referred to in studies on learning and memory mechanisms and their physiological correlate, the long-term potentiation (LTP). The three sets of synapses are formed by the fibers of perforant pathway terminating on granule cells and by the mossy fibers and Schaeffer collaterals making connections with the pyramidal cells. Each of the three types of synapses can develop LTP. LTP is accompanied by changes in gene expression and it is the nuclear transcription, involving specific transcription factors, that is the starting point for the series of biological amplifications and consolidations both necessary for such sustained changes. The transcription factors are proteins that control gene expression, development and functional formation in every eukaryotic cell. Two categories of transcription factors have been defined to date: general factors that comprise at least 20 proteins to form multiple preinitiation complex at the TATA box (TATA rich sequence) or regulatory factors that bind to promoter or enhancer regions at specific sites on the DNA close to, or distant from, the TATA box. Transcription factors have been divided into five different major classes according to unique protein motifs. These include basic domain, zinc-finger, helix-turn-helix, beta-Scaffold factors with minor groove contacts and other transcription factors not specifically classified. Much evidence has been accumulating in favor of the participation of several transcription factors in the consolidation of memory in the mammalian hippocampus following a spatial memory task. It is, therefore, of great importance that the involvement of transcription factors in de novo protein synthesis relevant to the synaptic mechanisms that mediate the formation of long-term memory should be summarized and discussed. No specific correlation between transduction of extracellular signals and expression of nuclear transcription factors, however, has been demonstrated to date.

Astrocyte-derived factors modulate the inhibitory effect of ethanol on dendritic development

Numerous studies in vivo and in vitro have demonstrated that ethanol disrupts neuromorphogenesis. However, it has not been determined what role, if any, is played by non-neuronal cells in mediating this effect. We recently reported that ethanol inhibits dendritic development in low-density cultures of fetal rat hippocampal pyramidal neurons (Yanni and Lindsley, 2000: Dev Brain Res 120:233-243). In this culture system, cortical astrocytes precondition neuronal culture media for 2 days before the addition of neurons, which then develop on a separate substrate in coculture with the astrocytes. To determine whether astrocyte response to ethanol mediates the effects of ethanol on neurons, the present study compared dendritic development of neurons after 6 days in medium containing 400 mg/dl ethanol in coculture with live astrocytes and in conditioned medium from astrocytes that were never exposed to ethanol. The same experiment was also performed with and without ethanol present during astrocyte preconditioning of the medium. The effects of ethanol differed depending on when it was added to the cultures relative to addition of newly dissociated neurons. However, the effects of ethanol were not related to whether neurons were cocultured with live astrocytes. When astrocytes preconditioned the medium normally, ethanol added at plating inhibited dendritic development of neurons regardless of whether they were maintained in coculture with live astrocytes or in conditioned medium. In surprising contrast, the presence of ethanol during astrocyte preconditioning of the media had a growth promoting effect on subsequent dendrite development despite the continued presence of ethanol in the medium. Thus, astrocytes release soluble factors in response to ethanol that can protect neurons from the inhibitory effects of ethanol on dendritic growth, but the timing of neuronal exposure to these factors, or their concentration, may influence their activity.

Ethanol inhibits development of dendrites and synapses in rat hippocampal pyramidal neuron cultures

Evidence suggests that some neuropathologic manifestations of Fetal Alcohol Syndrome (FAS) result from the disruption of neuromorphogenesis and synapse formation in the hippocampus. Prior research in this laboratory has shown that ethanol in the medium during the first 24 h in culture increases the number of minor processes (the precursors of axons and dendrites) and accelerates the rate at which axons are formed in low-density cultures of embryonic rat hippocampal neurons. The current study examined the effects of ethanol on the subsequent development of dendrites and synapses in these cultures. Quantitative morphometric analysis utilized double-immunofluorescent staining for MAP2 and synapsin I to visualize dendrites and synaptic specializations, respectively. Six days of ethanol (200, 400 or 600 mg/dl) in the medium, beginning at the time of plating, resulted in decreases in total dendritic length per cell, dendrite number per cell, length of individual dendrites and synapse number per innervated dendrite but had no effect on cell survival. The decrease in synapse number was correlated with dendrite length, suggesting that ethanol's effects on synapse number are secondary to its effects on dendritogenesis. Taken together with our previous findings, these results are the first to demonstrate that ethanol has differential effects on axonal and dendritic growth in a culture model of neurons that are vulnerable to ethanol-induced cytoarchitectural abnormalities during development in vivo.

Alcohol reduces neurofilament protein levels in primary cultured hippocampal neurons

High concentrations of alcohol (> or = 1.8%) were shown previously to impair health and viability of cultured hippocampal neurons. Because neurofilament proteins are essential for neuronal process outgrowth and differentiation, the effects of alcohol on these proteins were determined in the neuronal processes of primary cultured gestational day 18 rat hippocampal neurons. At the relatively lower concentrations used in the present study, alcohol caused a concentration-dependent reduction (< or = 47%) in 68 and 200 kDa neurofilament proteins (p < 0.05). Alcohol caused a 32% downward trend in 160 kDa neurofilament protein levels. Alcohol up to 1% (72-h exposure) produced no obvious alterations in neurite extension or explant morphology, and there were no visual signs of cell death. The sensitive MTT dye reduction assay showed no biochemical evidence of decreased cell viability at < or = 0.5% alcohol. The 32-47% reductions in neurofilament protein levels in vitro may hold implications for later hippocampal neuronal differentiation events in animals prenatally exposed to alcohol.

Ethanol-exposed central neurons fail to migrate and undergo apoptosis

Prenatal exposure of human brain to ethanol impairs neuronal migration and differentiation and causes mental retardation. The present results indicate that the adverse effects of ethanol on brain development may be partly due to the ethanol-induced disturbance of neuronal interaction with laminin, a protein involved in neuronal migration and axon guidance. This report shows that physiological concentrations (IC50 = 28 mM) of ethanol inhibit neurite outgrowth and neuronal migration of the rat cerebellar granule neurons on a laminin substratum. The ethanol-treated granule neurons undergo apoptosis, degrade their laminin substratum, and appear to release and bind increased amounts of the B2-chain-derived peptides along their surfaces. A protease inhibitor aprotinin, and the NMDA receptor channel, and voltage-gated calcium channel antagonist MK801 partially protect cerebellar granule neurons from ethanol-induced neurotoxicity. These results imply that ethanol-treated granule neurons resemble the granule neurons of the homozygous weaver mouse cerebellum with respect to their apoptosis, laminin expression, and partial rescue by approtinin and MK-801. Thus, ethanol may influence neuronal survival and neurite outgrowth via molecular pathways similar to those involved in neuronal death in other neurodegenerative processes of the central nervous system.

Effects of prenatal ethanol exposure on voltage-dependent calcium entry into neonatal whole brain-dissociated neurons

The effect of prenatal ethanol exposure on voltage-dependent calcium entry into neonatal-dissociated neurons was studied. Dissociated whole brain cells were isolated from neonates of prenatally ethanol-treated (ET), pair-fed (PF) control, and ad libitum (AL) control groups and loaded with fura-2. Prenatal ethanol exposure resulted in a significant reduction of calcium entry into K(+)-depolarized cells, compared with AL and PF control treatments. Initially, in dissociated cells from AL control animals, it was found that nifedipine (1 microM), omega-agatoxin (100 nM), and omega-conotoxin (500 nM), to a much lesser extent, significantly inhibited the 45 mM KCl-stimulated calcium entry. To determine the inhibitory action of prenatal ethanol exposure on N-, P-, and L-type voltage-dependent calcium channels, treatment of neonatal-dissociated neurons with different combinations of omega-conotoxin, omega-agatoxin, and nifedipine, respectively, was compared in the prenatal ethanol and control treatment groups. The inhibition of K(+)-stimulated increase in calcium entry by prenatal ethanol exposure was significantly less in the presence or absence of single antagonist conditions (ET < AL and PF). There was no apparent interaction of ethanol exposure and antagonist condition. However, the reduced calcium entry after prenatal ethanol exposure was superseded by the stronger inhibition in dual and triple antagonist conditions. The magnitude of the calcium response inhibition by the antagonist combinations was similar among the ET, PF, and AL groups. Thus, these results suggest that prenatal ethanol exposure decreases voltage-dependent calcium entry into neonatal-dissociated neurons in a manner that does not seem to involve the selective inhibition of any individual N-, P-, or L-type calcium channel.

Exposure of embryonic cells to alcohol: contrasting effects during preimplantation and postimplantation development

Alcohol is a known teratogen that causes a broad variety of developmental anomalies, including fetal growth retardation, craniofacial anomalies, and neurological disorders. The etiology of this multiple defect syndrome, known as fetal alcohol syndrome, has been studied in animal models that reproduce many of the attributes of the human disease. These studies show that ethanol is most teratogenic during organogenesis and development of the nervous system. The molecular basis of fetal alcohol effects has been further investigated using embryo and cell culture systems. Recent studies show that signal transduction pathways controlling cell proliferation are perturbed during ethanol exposure. Ethanol can induce the release of intracellular calcium stores, which stimulates the cell cycle, and it also up-regulates the expression of myc proteins associated with cell proliferation. Increased proliferation is advantageous during the preimplantation period, but ethanol interference with terminal differentiation events within developing tissues during organogenesis may underlie alcohol teratogenicity.