Ethanol-responsive gene expression in neural cell cultures

The regulation of neuronal gene expression by alcohol

In recent years there has been an explosion of interest in how genes regulate alcohol drinking and contribute to alcoholism. This work has been stimulated by the completion of the human and mouse genome projects and the resulting availability of gene microarrays. Most of this work has been performed in drinking animals, and has utilized the extensive genetic variation among different mouse strains. At the same time, a much smaller amount of effort has gone into the in vitro study of the mechanisms underlying the regulation of individual genes by alcohol. These studies at the cellular and sub-cellular level are beginning to reveal the ways in which alcohol can interact with the transcriptional, translational and post-translational events inside the cell. Detailed studies of the promoter regions within several individual alcohol-responsive genes (ARGs) have been performed and this work has uncovered intricate signaling pathways that may be generalized to larger groups of ARGs. In the last few years several distinct ARGs have been identified from 35,000 mouse genes, by both the "top-down" approach (ex vivo gene arrays) and the "bottom-up" methods (in vitro promoter analysis). These divergent methodologies have converged on a surprisingly small number of genes encoding ion channels, receptors, transcription factors and proteins involved in synaptic function and remodeling. In this review we will describe some of the most interesting cellular and microarray work in the field, and will outline specific examples of genes for which the mechanisms of regulation by alcohol are now somewhat understood.

Pharmacogenomic analysis of mechanisms mediating ethanol regulation of dopamine beta-hydroxylase

We previously showed that ethanol regulates dopamine beta-hydroxylase (DBH) mRNA and protein levels in human neuroblastoma cells (Thibault, C., Lai, C., Wilke, N., Duong, B., Olive, M. F., Rahman, S., Dong, H., Hodge, C. W., Lockhart, D. J., and Miles, M. F. (2000) Mol. Pharmacol. 58, 1593-1600). DBH catalyzes norepinephrine synthesis, and several studies have suggested a role for norepinephrine in ethanol-mediated behaviors. Here, we performed a detailed analysis of mechanism(s) underlying ethanol regulation of DBH expression in SH-SY5Y cells. Transient transfection analysis showed that ethanol (25-200 mM) caused concentration- and time-dependent increases in DBH gene transcription. Progressive deletions identified ethanol-responsive sequences in the -262 to -142 bp region of the DBH gene promoter. Mutagenesis of cAMP-response element (CRE) sequences in this region abolished ethanol responsiveness while maintaining responsiveness to phorbol esters. Coexpression of dominant-negative CRE-binding protein greatly reduced ethanol induction of DBH. Inhibitors of protein kinase A, casein kinase II, and MAPK reduced ethanol induction of DBH promoter activity. Pharmacogenomic studies with microarrays showed that protein kinase A, MEK, and casein kinase II inhibitors blocked induction of DBH and a large subset of ethanol-responsive genes. These genes had diverse functional groupings, including multiple members of the MAPK and phosphatidylinositol signaling cascades. Real-time PCR analysis validated select microarray results. Taken together, these results suggest that ethanol regulation of DBH requires a functional CRE and its binding protein and may require interaction of multiple kinase pathways. This mechanism may also mediate ethanol responsiveness of a complex subset of genes in neural cells. These studies may have implications for behavioral responses to ethanol or mechanisms underlying ethanol-related neurological disease.

The effects of chronic ethanol consumption on neurotrophins and their receptors in the rat hippocampus and basal forebrain

Damage to the basal forebrain frequently results in deficits in learning and memory. Mnenonic dysfunction also occurs following prolonged ethanol consumption in humans and in animal models of chronic ethanol intake, accompanied by specific abnormalities in synaptic transmission between the basal forebrain and hippocampus. The integrity of at least some of the reciprocal neuronal connections between these brain regions is influenced by target-derived neurotrophic factors. We used a semiquantitative reverse transcription polymerase chain reaction technique to measure the messenger RNA for neurotrophins BDNF and NGF, and for their receptors trkB, trkA, and the low affinity receptor, p75(NTR) in the hippocampus and basal forebrain of rats after 28 weeks of alcohol consumption without malnutrition. This chronic ethanol treatment (CET) resulted in a marked and selective reduction in basal forebrain trkA mRNA. Western blotting revealed a similar reduction of basal forebrain trkA protein. CET effects on basal forebrain trkA may reflect impaired NGF signaling that could compromise septohippocampal synaptic connections, cholinergic differentiation, and emergent functional abilities dependent on these properties.

Ethanol induces rapid lipid peroxidation and activation of nuclear factor-kappa B in cerebral vascular smooth muscle: relation to alcohol-induced brain injury in rats

The present study was designed to test the hypothesis that acute administration of alcohol (ethanol) to primary cultured cerebral vascular smooth muscle cells will cause lipid peroxidation, inhibition of IkappaB phosphorylation, and inhibition of nuclear transcription factor-kappa B (NF-kappaB). Ethanol (10, 25, 100 mM) resulted in concentration-dependent rises in malondialdehyde in as little as 30-45 min after exposure to the alcohol, rising to levels 2.5-10x normal after 18-24 h. Using EMSA assays and specific antibodies, ethanol caused three DNA-binding proteins (p50, p65, c-Rel) to rise in nuclear extracts in a concentration-dependent manner. Using a rabbit antibody, IkappaB phosphorylation (and degradation) was stimulated by ethanol (in a concentration-dependent manner) and inhibited by a low concentration of the NF-kappaB inhibitor, pyrrolidine dithiocarbamate. These new biochemical and molecular data indicate that ethanol, even in physiologic concentrations, can elicit rapid lipid peroxidation and activation of NF-kappaB in cerebral vascular muscle cells. The present results when viewed in light of other recently published data suggest that ethanol-induced lipid peroxidation and activation of nuclear transcription factors probably play important roles in alcohol-induced brain-vascular damage, neurobehavioral actions and stroke.

Ethanol-regulated gene expression of neuroendocrine specific protein in mice: brain region and genotype specificity

Neuroendocrine specific protein or reticulon 1 (NSP/RTN1) was identified as a putative ethanol-regulated gene using mRNA differential display in mice genetically selected for severe ethanol withdrawal (withdrawal seizure-prone, WSP). One transcript of RTN1 (3.0 kb) showed a statistically significant increase (13%) in relative abundance in whole brain of ethanol-treated WSP mice but not in mice selected for resistance to ethanol withdrawal convulsions (WSR). We hypothesized that ethanol-induced regulation of gene expression of mRTN1 is specific to mice predisposed to exhibit severe ethanol withdrawal and that the gene might be regulated differentially in specific brain regions. WSP and WSR selected lines and DBA/2J and C57BL/6J inbred strains of mice were exposed to ethanol vapor or air for 72 h. mRNA steady-state expression of RTN1 was assessed in hippocampus, cortex, and cerebellum. Results indicated that the pattern of ethanol-induced changes in gene expression was dependent upon transcript size, brain region, and genotype. Modest increases in the relative abundance of both transcripts of RTN1 were observed in the hippocampus and cortex of all ethanol-treated mice. Results from cerebellum showed a moderate decrease in expression of RTN1 (3.0 kb transcript) in WSP and DBA/2J mice, but not in the mice resistant to ethanol withdrawal (C57BL/6J and WSR). These results suggest a genotype-specific effect of chronic ethanol exposure on steady-state mRNA levels of RTN1 in the cerebellum. Overall, the results indicate a complex pattern of ethanol-induced regulation of the putative mouse homologue of RTN1 and suggest that specific brain regional changes may be involved in the expression of physical dependence.

Antioxidants prevent ethanol-induced contractions of canine cerebral vascular smooth muscle: relation to alcohol-induced brain injury

The present study was designed to test the hypothesis that alpha-tocopherol (Vit. E) and pyrrolidine dithiocarbamate (PDTC) might exert direct effects on alcohol-induced contractions of canine basilar cerebral arteries. After precontraction of arterial ring segments with ethanol, PDTC (10(-8)-10(-6) M) and Vit. E (10(-6)-10(-4) M) induced concentration-dependent relaxations of cerebral arteries, compared to untreated controls. The effective concentrations producing approximately 50% of the maximal relaxation responses (EC(50) values) were about 2.48+/-0.09 x 10(-7) M for PDTC, and 1.87+/-0.10 x 10(-5) mM for Vit. E, respectively. Preincubation of these arterial rings with EC(50)'s of PDTC or Vit. E for 40 min attenuate markedly the contractions produced by alcohol, at concentrations of 1-400 mM. However, both PDTC and Vit.E do not relax equi-potent precontractions induced by either KCl or prostaglandin F(2alpha) (PGF(2alpha)) or inhibit their contractions. These data suggest that alcohol-induced contractions of cerebral arteries are mediated via excitation-contraction coupling pathways different from those used by KCl or receptor-mediated agonists such as PGF(2alpha). The present results, when viewed in light of other recently published data, suggest that antioxidants may prove useful in the amelioration and treatment of alcohol-induced brain damage and strokes.

Pyrrolidine dithiocarbamate prevents ethanol-induced elevation of [Ca2+]i in cultured canine cerebral vascular smooth muscle cells

Pyrrolidine dithiocarbamate (PDTC) has been shown to block nuclear transcription factor (NF-kappaB) activation induced by a wide range of stimuli in different cell lines. NF-kappaB is a common element of the promoter region of inflammatory cytokines which can be stimulated by ethanol. Recently, we have shown that PDTC can ameliorate cerebrovascular damage, brain cortical damage, leukocyte adhesion and rolling, and stroke induced by ethanol. We, therefore, tested the effects of preincubation with PDTC on alcohol-induced changes in intracellular free calcium ions ([Ca2+]i) in cultured canine cerebral smooth muscle cells. These vascular cells, chronically treated with ethanol (10-100 mM) for 24 and 72 h, exhibited concentration-dependent rises in [Ca2+]i. PDTC (0.1 microM) itself failed to influence resting levels of [Ca2+]i in these vascular muscle cells. PDTC (0.1 microM) pretreatment, however, inhibited completely the elevations in [Ca2+]i induced by chronic ethanol (10-100 mM). The present results suggest that ethanol-induced production of reactive oxygen species and elevation of [Ca2+]i in cultured canine cerebral vascular smooth muscle cells triggers induction of transcription factor NF-kappaB, which could play an important role in alcohol-induced brain damage and stroke.

Ethanol induces MAP2 changes in organotypic hippocampal slice cultures

Microtubule-associated protein 2 (MAP2) and neuron-specific protein (NeuN) immunostains were used to demonstrate neurotoxic effects in mature hippocampal slice cultures exposed to ethanol (50, 100, 200 mM) for 4 weeks. At the low dose the density of MAP2 immunostaining in the dentate molecular layer was 118% of the control cultures, with no detectable changes in CA1 and CA3. At 100 mM no changes were detected, while 200 mM ethanol significantly reduced the MAP2 density in both dentate (19%) and hippocampal dendritic fields (CA3, 52%; CA1, 55%). At this dose NeuN staining showed considerable loss of CA3 pyramidal cells and moderate loss of dentate granule cells, as seen in vivo. The results indicate that brain slice cultures combined with immunostaining for cytoskeleton and neuronal markers can be used for studies of ethanol and organic solvent neurotoxicity.

Identification of specific mRNAs affected by treatments producing long-term facilitation in Aplysia

Neural correlates of long-term sensitization of defensive withdrawal reflexes in Aplysia occur in sensory neurons in the pleural ganglia and can be mimicked by exposure of these neurons to serotonin (5-HT). Studies using inhibitors indicate that transcription is necessary for production of long-term facilitation by 5-HT. Several mRNAs that change in response to 5-HT have been identified, but the molecular events responsible for long-term facilitation have not yet been fully described. To detect additional changes in mRNAs, we investigated the effects of 5-HT (1.5 hr) on levels of mRNA in pleural-pedal ganglia using in vitro translation. Four mRNAs were affected by 5-HT, three of which were identified as calmodulin (CaM), phosphoglycerate kinase (PGK), and a novel gene product (protein 3). Using RNase protection assays, we found that 5-HT increased all three mRNAs in the pleural sensory neurons. CaM and protein 3 mRNAs were also increased in the sensory neurons by sensitization training. Furthermore, stimulation of peripheral nerves of pleural-pedal ganglia, an in vitro analog of sensitization training, increased the incorporation of labeled amino acids into CaM, PGK, and protein 3. These results indicate that increases in CaM, PGK, and protein 3 are part of the early response of sensory neurons to stimuli that produce long-term facilitation, and that CaM and protein 3 could have a role in the generation of long-term sensitization.

Ethanol-induced intracellular calcium mobilization rapidly alters gene expression in the mouse blastocyst

The induction of intracellular Ca2+ release in pre-implantation mouse embryos accelerates their subsequent rate of development in vitro through a calmodulin-dependent mechanism [Stachecki J.J., Armant D.R. Transient release of calcium from inositol 1,4,5-trisphosphate-specific stores regulates mouse pre-implantation development. Development 1996; 122: 2485-2496]. To examine the hypothesis that intracellular Ca2+ signaling alters embryonic gene expression, individual transcript levels were compared by mRNA differential display before and 1 h after intracellular Ca2+ mobilization with ethanol in mouse blastocysts. Ten up-regulated and four down-regulated genes were observed, representing 3.5% of approximately 400 transcripts that were resolved. After sequencing, most of the DNA fragments appeared to be novel; however, two amplicons that increased after Ca2+ mobilization were identified as arginase and ubiquitin conjugating enzyme (E2). The up-regulation of arginase mRNA (3.5-fold after 2 h) was confirmed by reverse transcription and the polymerase chain reaction using specific oligonucleotide primers derived from the deduced mouse embryo sequence. A corresponding 2.5-fold increase in arginase enzymatic activity peaked 9 h after ethanol exposure. Increased expression of arginase and other genes may mediate the onset of rapid cell proliferation and differentiation that is induced by Ca2+ signaling during pre-implantation development.

Transcriptional regulation of tracheo-bronchial mucin (TBM) gene by ethanol

The epithelia of the respiratory tract are protected by a mucin glycoprotein. The expression of mucin changes when epithelia come in contact with toxic agents such as ethanol. Previously, we have identified and characterized the expression of a tracheo-bronchial mucin (TBM) gene. In the present study, we observed that ethanol regulates TBM expression at the transcription level. Ethanol enhanced the expression of TBM mRNA in a dose- and time-dependent manner in HBE1 cells. At 100 mM concentration (a concentration reported to be present in alcoholics), ethanol induced an eight-fold increase in TBM transcription as determined by reporter gene expression analysis.

Prenatal ethanol exposure alters the expression of intestinal hydrolase mRNAs in newborn rats

To gain insight into the postnatal growth delay induced by ethanol in utero, we characterized functional impairments of the small intestine of neonatal rats prenatally exposed to ethanol using a well-described model of gestational alcoholism (25% ethanol w/v in the drinking water). Expression of the intestinal enzymes-lactase-phlorizin hydrolase (LPH) and intestinal alkaline phosphatase (IAP)-that are critical for enteral nutrition of neonates was studied. Characteristic patterns of LPH and IAP expression along the proximal-distal (horizontal) and crypt-villus (vertical) axes of the small intestine, as well as the intracellular localization of LPH and IAP mRNAs and immunoreactive proteins within absorptive enterocytes, were not altered by prenatal exposure to ethanol. However, a 10- to 15-fold increase in the number of LPH and IAP mRNA molecules per absorptive enterocyte was found throughout the intestine of ethanol-exposed neonates, compared with controls, whereas lactase and alkaline phosphatase activities per enterocyte remained unchanged. These findings suggest that ethanol in utero alters the mRNA abundance of epithelial enzymes in newborn rat small intestine. Changes in mRNA abundance could be an important aspect of enterocyte adaptation to high ethanol concentrations in gastrointestinal amniotic fluid of ethanol-exposed fetuses.

Identification of the nuclear transcription factor NFkappaB in rat after in vivo ethanol administration

NFkappaB, a nuclear transcription factor, was induced in the brain nuclear fraction of naive rats after an acute injection of ethanol, 2 g/kg. In contrast, rats which had been chronically alcoholised showed the constitutively active NFkappaB-like complex only after a further acute dose of ethanol. Hepatic nuclear fractions did not exhibit the specific NFkappaB-like complex during the first 45 min after acute ethanol injection, beyond that which was normally constitutively present. Such activation of NFkappaB-like complex in the brains of the naive rats may play an important role in the cellular protective response.

Interaction of ethanol with inducers of glucose-regulated stress proteins. Ethanol potentiates inducers of grp78 transcription

GRP78, a molecular chaperone expressed in the endoplasmic reticulum, is a "glucose-regulated protein" induced by stress responses that deplete glucose or intracisternal calcium or otherwise disrupt glycoprotein trafficking. Previously we showed that chronic ethanol exposure increases the expression of GRP78. To further understand the mechanism underlying ethanol regulation of GRP78 expression, we studied the interaction between ethanol and classical modulators of GRP78 expression in NG108-15 neuroblastoma x glioma cells. We found that, in addition to increasing basal levels of GRP78 mRNA ("induction"), ethanol produced greater than additive increases in the induction of GRP78 mRNA by the "classical" GRP inducers A23187, brefeldin A, and thapsigargin ("potentiation"). Both the ethanol induction and potentiation responses modulated grp78 gene transcription as determined by stable transfection analyses with the rat grp78 promoter. Ethanol potentiated the action of all classical inducers of grp78 transcription that were studied. In contrast, co-treatment with the classical GRP inducers thapsigargin and tunicamycin produced only simple additive increases in grp78 promoter activity. Transient transfection studies with deletion mutants of the rat grp78 promoter showed that cis-acting promoter sequences required for ethanol induction differ from those mediating responses to classical GRP inducers. Furthermore, linker-scanning mutations of the grp78 promoter suggested that the ethanol potentiation response required a cis-acting promoter element different from those involved in induction by ethanol or classical inducing agents. While the ethanol induction response required 16-24 h to be detectable, ethanol potentiation of thapsigargin occurred within 6 h. The potentiation response also decayed rapidly after ethanol removal. In addition, the protein kinase A inhibitor Rp-cAMPS and protein phosphatase inhibitor okadaic acid both increased ethanol potentiation of thapsigargin while Sp-cAMPS, an activator of protein kinase A, decreased ethanol potentiation. Taken together, our findings suggest two mechanisms by which ethanol regulates grp78 transcription, both differing from the action of classical GRP inducers such as thapsigargin. One mechanism (potentiation) involves a protein phosphorylation cascade and potentiates the action of classical GRP inducers. In contrast, GRP78 induction by ethanol involves promoter sequences and a mechanistic pathway separate from that of the ethanol potentiation response or classical GRP78 inducers. These studies show that ethanol produces a novel and complex regulation of grp78 transcription which could be of particular importance during neuronal exposure to GRP-inducing stressors as might occur with central nervous system injury.

Regulation of the stress-like protein adenotin in PC 12 cells by ethanol exposure

The effects of chronic ethanol exposure on the stress-like protein adenotin were investigated using the radioligand [3H]-5'-N-ethylcarboxamidoadenosine ([3H]NECA). A 4-day exposure to 150 mM ethanol increased both the KD and the density of [3H]NECA binding sites. These changes were not due to residual ethanol as the acute addition of ethanol did not alter [3H]NECA binding. Chronic ethanol exposure of A126-1B2-1 cells, which are a mutant PC 12 cell line deficient in protein kinase A (PKA), increased the cellular density of adenotin, but did not affect the KD for the radioligand. Conversely, when PC 12 cells were exposed to 10 microM forskolin for either 2 or 4 days, the cellular density of adenotin was not altered, but the affinity of adenotin for [3H]NECA was reduced significantly. An increase in KD was not observed after a 1-hr exposure of PC 12 cells to forskolin, indicating that the reduction in affinity for the radioligand was not due simply to a PKA-mediated phosphorylation of adenotin. The present study demonstrated that chronic ethanol regulates adenotin through two different mechanisms. The ethanol-induced increase in the density of adenotin does not involve PKA, while the reduction in affinity ap pears to involve a cAMP-dependent mechanism.

Ethanol-induced single-strand DNA breaks in rat brain cells

Male Sprague-Dawley rats were intubated with 4 g/kg body weight of ethanol (in a 20%, v/v, water solution). Brain cells were analyzed for single-strand DNA breaks at various post-ethanol administration time points using an alkaline microgel electrophoresis assay. Results showed a significant increase in single-strand DNA breaks in brain cells that peaked at approx. 4 h and returned to control level within 6 h after ethanol administration.

Ethanol inhibits insulin receptor substrate-1 tyrosine phosphorylation and insulin-stimulated neuronal thread protein gene expression

Neuronal thread proteins (NTPs) are molecules that accumulate in the brains of patients with Alzheimer's disease, and may play a key role in both normal and neurodegenerative neuritic sprouting. In this investigation we determined whether NTP expression is up-regulated by insulin, an important neurotrophic factor that stimulates differentiation-associated neurite outgrowth, and studied the effects of ethanol, a known inhibitor of growth factor receptor tyrosine phosphorylation, on NTP expression and insulin-mediated signal transduction cascade in neuronal [primitive neuroectodermal tumour cell line 2; (PNET2)] cells. PNET2 cells were treated with 50 m-units/ml insulin in the presence or absence of 100 mM ethanol for 0.2-96 h, and cell proliferation and expression of NTP molecules were investigated by metabolic labelling, immunoprecipitation and immunohistochemical staining. Insulin stimulation resulted in an immediate increase in the levels of three (38, 18 and 15 kDa) of five NTP species (the others were of 26 and 21 kDa), followed by a decline in expression within 120 min; however, studies performed up to 96 h of culture demonstrated up-regulation by insulin of all five NTP species. Ethanol either abolished or severely muted the short- and long-term insulin-mediated upregulation of NTP expression, and substantially reduced insulin-mediated neuronal differentiation. The effects of ethanol on NTP gene expression were associated with impaired insulin-mediated tyrosine phosphorylation of both the insulin receptor beta subunit and the insulin receptor substrate-1 (IRS-1), resulting in decreased association of phosphatidylinositol 3-kinase with IRS-1. The findings suggest that ethanol may inhibit NTP expression associated with central nervous system neuronal differentiation by uncoupling the IRS-1-mediated insulin signal transduction pathway.

Induction of HSP72 in rat liver by chronic ethanol consumption combined with exercise: association with the prevention of ethanol-induced fatty liver by exercise

Ethanol-induced fatty liver in rats was attenuated by repeated running exercise, and the protective effect of exercise was associated with the synergistic expression of heat shock proteins (HSP72). Rats were placed in four groups of six. The two ethanol-fed groups of rats received a liquid diet (Lieber-DeCarli formulation) in which 36% of the calories were derived from ethanol. One group remained sedentary (S/E), whereas the other was trained to run on a rodent treadmill at a speed of 27 m/min, 1 hr/day, 5 days/week, for 7 weeks (R/E). Two other groups--one exercised as previously mentioned (R/C) and one sedentary (S/C)--received control-liquid diets in which the ethanol was isocalorically substituted with a dextran/maltose mixture. The degree of fatty infiltration in liver sections stained with hematoxylin and eosin was graded on a 0-4 scale and the data analyzed by ANOVA on ranks. Ethanol significantly induced fatty infiltration in the S/E group, whereas fatty infiltration in the livers of the R/E group was not different from the S/C group. Electrophoresis and Western blotting of liver homogenates demonstrated that HSP72 was not expressed in either the S/C or S/E groups and was only slightly expressed in the R/C group. The combination of exercise and ethanol, however, resulted in an elevated expression of HSP72 in the R/E group. The content of HSP73 was unaffected by any treatment.

Ethanol-induced reduction of the amount of stimulatory GTP-binding regulatory protein, Gs, in wild-type S49 murine lymphoma cells: effect of cycloheximide and puromycin

The activity and the amount of Gs in wild-type S49 murine lymphoma cells decreased by 16-18% and by 29%, respectively, after 24 h treatment of the cells with 50 mM ethanol, through a transient increase of the Gs activity with no alteration in its content after 4 and 8 h treatment. No decrease of the Gs activity was noted when membranes from S49 cells were treated with 50-500 mM ethanol. To study the role of protein metabolism in the ethanol-induced reduction in the amount of Gs, S49 cells were treated with ethanol for 24 h in the presence of inhibitor of protein synthesis. Cycloheximide at concentrations of 0.05-0.15 micrograms/ml and puromycin at 0.15-0.60 micrograms/ml caused a dose-dependent inhibition of cell division in S49 cells to a similar degree. The ethanol-induced reduction of the activity and the amount of Gs was completely abolished by those concentrations of cycloheximide, but not by puromycin. Cycloheximide itself caused no alteration in the Gs activity of S49 cell membranes. These results indicate that the process of the ethanol-induced event of Gs involves cycloheximide-sensitive protein synthesis.

Ethanol and naloxone differentially upregulate delta opioid receptor gene expression in neuroblastoma hybrid (NG108-15) cells

We have used a sensitive solution hybridization assay with a riboprobe transcribed from the coding sequence of the delta opioid receptor (DOR) to quantitate the changes in DOR mRNA transcript levels following exposure of NG108-15 cells to ethanol and/or the opioid antagonist, naloxone. Incubation of NG108-15 cells with 200 mM ethanol or 1 microM naloxone, treatments that have previously been shown to upregulate DOR binding, increased DOR mRNA transcript levels 2 to 3 fold. DOR mRNA levels peaked at 24 to 48 h after exposure to either ethanol or naloxone. At 168 h, DOR mRNA levels in NG108-15 cells exposed to naloxone had returned to control (untreated) levels while the levels in ethanol treated cells remained nearly equal to peak values. Exposure to a combination of ethanol plus naloxone for 24 h produced an additive effect, so that DOR mRNA transcripts were increased 3 fold. Northern blot analysis identified six DOR transcript bands ranging in size from 8.7 to 2.1 kb. The above treatments increased each of the six bands proportionately, so that no difference was observed in the fraction of the total hybridization signal produced by each band of the Northern blot. These results demonstrate that each of the DOR transcripts in NG108-15 cells are subject to homologous (naloxone) as well as heterologous (ethanol) upregulation.

A single administration of ethanol simultaneously increases c-fos mRNA and reduces c-jun mRNA in the hypothalamus and hippocampus

We have previously demonstrated that a single administration of ethanol induces the expression of c-fos mRNA in the hypothalamic paraventricular nucleus (PVN). However, Fos protein must interact with a member of the Jun family to form functional heterodimers. To determine whether ethanol may have differential effects on c-fos and c-jun expression, we injected male rats acclimated to a 25 degrees C environment with ethanol (3 g/kg b.wt.) or saline. Using in situ hybridization histochemistry with oligonucleotide probes, we found that ethanol increased c-fos mRNA in the PVN, but decreased c-jun mRNA both in the PVN and in hippocampus. Considering that ethanol produces hypothermia and that the PVN contains neurons activated during hypothermia, we evaluated the effect of cold on c-fos and c-jun mRNA. Both cold and ethanol increased c-fos mRNA, and the effects were additive. However, c-jun mRNA levels in both PVN and hippocampus were unaffected by temperature. Finally, c-jun mRNA levels in the hippocampus were significantly reduced by chronic ethanol exposure, and this trend was also observed in the PVN. These findings demonstrate that a single injection of ethanol has opposite effects on the expression of nuclear transcription factors which interact to regulate gene expression in the nervous system.

Phosducin-like protein: an ethanol-responsive potential modulator of guanine nucleotide-binding protein function

Acute and chronic exposure to ethanol produces specific changes in several signal transduction cascades. Such alterations in signaling are thought to be a crucial aspect of the central nervous system's adaptive response, which occurs with chronic exposure to ethanol. We have recently identified and isolated several genes whose expression is specifically induced by ethanol in neural cell cultures. The product of one of these genes has extensive sequence homology to phosducin, a phosphoprotein expressed in retina and pineal gland that modulates trimeric guanine nucleotide-binding protein (G protein) function by binding to G-protein beta gamma subunits. We identified from a rat brain cDNA library an isolate encoding the phosducin-like protein (PhLP), which has 41% identity and 65% amino acid homology to phosducin. PhLP cDNA is expressed in all tissues screened by RNA blot-hybridization analysis and shows marked evolutionary conservation on Southern hybridization. We have identified four forms of PhLP cDNA varying only in their 5' ends, probably due to alternative splicing. This 5'-end variation generates two predicted forms of PhLP protein that differ by 79 aa at the NH2 terminus. Treatment of NG108-15 cells for 24 hr with concentrations of ethanol seen in actively drinking alcoholics (25-100 mM) causes up to a 3-fold increase in PhLP mRNA levels. Induction of PhLP by ethanol could account for at least some of the widespread alterations in signal transduction and G-protein function that are known to occur with chronic exposure to ethanol.

Ethanol-induced changes in astrocyte gene expression during rat central nervous system development

Disruption of spatial and temporal patterns of gene expression in cells of the developing brain could result in abnormal development. We report that briefly exposing neonatal rats to a moderate dose of ethanol on postnatal days 5 through 7 caused a large, specific increase in glial fibrillary acidic protein (GFAP) mRNA and GFAP. Astrocytes of the cerebral cortex were apparently more sensitive to this effect of ethanol than astrocytes in several other brain regions. As a first step in the characterization of an vitro model of ethanol's effect on GFAP gene expression, ethanol was added to the media of primary cultures of cortical astrocytes in a pattern of exposure and at concentrations equal to pups' peak blood levels. This resulted in an increase in GFAP mRNA whose magnitude and specificity mirrored that observed in the animal model. Together, these results suggest that even brief exposure to ethanol can alter gene expression in astrocytes, and forms the foundation for further characterization of an in vitro model that may be used to determine the mechanism of this effect.