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

Establishment of a Simple and Versatile Evaporation Compensation Model for in vitro Chronic Ethanol Treatment: Impact on Neuronal Viability

Alcohol overconsumption is a major cause of preventable mental disorders and death in the United States and around the world. The pathogenesis of alcohol dependence, abuse, and toxicity to the central nervous system remains incompletely understood. In vitro and cell culture-based models have been highly valuable in studying the molecular and cellular mechanisms underlying the contribution of individual CNS cell types to ethanol's effects on the brain. However, conventional cell culture model systems carry the inherent disadvantage of rapid loss of ethanol due to evaporation following a bolus addition at the start of the treatment. We have established a multi-well cell culture plate-based ethanol evaporation compensation model that utilizes the inter-well space as a reservoir to compensate for the evaporative loss of ethanol in the cell treatment wells. Following a single bolus addition at the start of the treatment, ethanol concentration rapidly decreased over time. Through compensation using the multi-well plate platform, maintenance of ethanol concentrations ranging from 10-100 mM was achieved for up to 72 hours in a cell-free system. Greater effects in ethanol-induced decrease in neuronal cell viability were observed with than without compensation. Our method effectively compensates for the evaporative loss of ethanol typically observed in the traditional method. This method provides an economic, simple and effective in vitro model system for ethanol treatment over an extended timeframe where maintenance of a relatively constant concentration of ethanol is desired.

Total Chemical Syntheses of the GM3 and F-GM3 Ganglioside Epitopes and Comparative Pre-Clinical Evaluation for Non-Invasive Imaging of Oligodendrocyte Differentiation

Gangliosides are intimately involved in a plenum of (neuro)inflammatory processes, yet progress in establishing structure-function interplay is frequently hindered by the availability of well-defined glycostructures. Motivated by the ubiquity of the ganglioside GM₃ in chemical neurology, and in particular by its conspicuous presence in myelin, the GM₃ epitope was examined with a view to preclinical validation as a tracer. The suitability of this scaffold for the noninvasive imaging of oligodendrocyte differentiation in Multiple sclerosis is disclosed. The stereocontrolled synthesis of a site-selectively fluorinated analogue (F-GM₃) is also disclosed to enable a comparative analysis in oligodendrocyte (OL) differentiation. Whereas the native epitope caused a decrease in the viability in a dose-dependent manner, the addition of distinct F-GM₃ concentrations over 48 h had no impact on the OL viability. This is likely a consequence of the enhanced hydrolytic stability imparted by the fluorination and highlights the potential of fluorinated glycostructures in the field of molecular imaging. Given the predominant expression of GM₃ in oligodendrocytes and the capacity of GM₃ to interact with myelin-associated proteins, this preclinical evaluation has revealed F-GM₃ to be an intriguing candidate for neurological imaging.

Chronic exposure to alcohol alters network activity and morphology of cultured hippocampal neurons

The effects of chronic exposure to moderate concentrations of ethanol were studied in cultured hippocampal neurons. Network activity, assessed by imaging of [Ca(2+)]i variations, was markedly suppressed following 5 days of exposure to 0.25-1% ethanol. The reduced activity was sustained following extensive washout of ethanol, but the activity recovered by blockade of inhibition with bicuculline. This reduction of network activity was associated with a reduction in rates of mEPSCs, but not in a change in inhibitory synaptic activity. Chronic exposure to ethanol caused a significant reduction in the density of mature dendritic spines, without an effect on dendritic length or arborization. These results indicate that chronic exposure to ethanol causes a reduction in excitatory network drive in hippocampal neurons adding another dimension to the chronic effects of alcohol abuse.

Prenatal alcohol exposure alters expression of neurogenesis-related genes in an ex vivo cell culture model

Prenatal alcohol exposure can lead to long-lasting changes in functional and genetic programs of the brain, which may underlie behavioral alterations seen in Fetal Alcohol Spectrum Disorder (FASD). Aberrant fetal programming during gestational alcohol exposure is a possible mechanism by which alcohol imparts teratogenic effects on the brain; however, current methods used to investigate the effects of alcohol on development often rely on either direct application of alcohol in vitro or acute high doses in vivo. In this study, we used our established moderate prenatal alcohol exposure (PAE) model, resulting in maternal blood alcohol content of approximately 20 mM, and subsequent ex vivo cell culture to assess expression of genes related to neurogenesis. Proliferating and differentiating neural progenitor cell culture conditions were established from telencephalic tissue derived from embryonic day (E) 15-17 tissue exposed to alcohol via maternal drinking throughout pregnancy. Gene expression analysis on mRNA derived in vitro was performed using a microarray, and quantitative PCR was conducted for genes to validate the microarray. Student's t tests were performed for statistical comparison of each exposure under each culture condition using a 95% confidence interval. Eleven percent of genes on the array had significantly altered mRNA expression in the prenatal alcohol-exposed neural progenitor culture under proliferating conditions. These include reduced expression of Adora2a, Cxcl1, Dlg4, Hes1, Nptx1, and Vegfa and increased expression of Fgf13, Ndn, and Sox3; bioinformatics analysis indicated that these genes are involved in cell growth and proliferation. Decreased levels of Dnmt1 and Dnmt3a were also found under proliferating conditions. Under differentiating conditions, 7.3% of genes had decreased mRNA expression; these include Cdk5rap3, Gdnf, Hey2, Heyl, Pard6b, and Ptn, which are associated with survival and differentiation as indicated by bioinformatics analysis. This study is the first to use chronic low to moderate PAE, to more accurately reflect maternal alcohol consumption, and subsequent neural progenitor cell culture to demonstrate that PAE throughout gestation alters expression of genes involved in neural development and embryonic neurogenesis.

Alcohol dysregulates corticotropin-releasing-hormone (CRH) promoter activity by interfering with the negative glucocorticoid response element (nGRE)

EtOH exposure in male rats increases corticotropin-releasing hormone (CRH) mRNA in the paraventricular nucleus of the hypothalamus (PVN), a brain region responsible for coordinating stress and anxiety responses. In this study we identified the molecular mechanisms involved in mediating these effects by examining the direct effects of EtOH on CRH promoter activity in a neuronal cell line derived from the PVN (IVB). In addition, we investigated the potential interactions of EtOH and glucocorticoids on the CRH promoter by concomitantly treating cells with EtOH and the glucocorticoid receptor (GR) antagonist RU486, and by sequentially deleting GR binding sites within glucocorticoid response element (GRE) on the CRH promoter. Cells were transiently transfected with a firefly luciferase reporter construct containing 2.5 kb of the rat wild type (WT) or mutated CRH promoter. Our results showed that EtOH treatment induced a biphasic response in CRH promoter activity. EtOH exposure for 0.5 h significantly decreased promoter activity compared to vehicle treated controls, whereas promoter activity was significantly increased after 2.0 h of EtOH exposure. Treatment with RU486, or deletion of the GR binding sites 1 and 2 within the GRE, abolished the EtOH-induced increase in the promoter activity, however did not affect EtOH-induced decrease in CRH promoter activity at an earlier time point. Overall, our data suggest that alcohol exposure directly regulates CRH promoter activity by interfering with the normal feedback mechanisms of glucocorticoids mediated by GR signaling at the GRE site of the CRH promoter.

Effects of ethanol and NAP on cerebellar expression of the neural cell adhesion molecule L1

The neural cell adhesion molecule L1 is critical for brain development and plays a role in learning and memory in the adult. Ethanol inhibits L1-mediated cell adhesion and neurite outgrowth in cerebellar granule neurons (CGNs), and these actions might underlie the cerebellar dysmorphology of fetal alcohol spectrum disorders. The peptide NAP potently blocks ethanol inhibition of L1 adhesion and prevents ethanol teratogenesis. We used quantitative RT-PCR and Western blotting of extracts of cerebellar slices, CGNs, and astrocytes from postnatal day 7 (PD7) rats to investigate whether ethanol and NAP act in part by regulating the expression of L1. Treatment of cerebellar slices with 20 mM ethanol, 10⁻¹² M NAP, or both for 4 hours, 24 hours, and 10 days did not significantly affect L1 mRNA and protein levels. Similar treatment for 4 or 24 hours did not regulate L1 expression in primary cultures of CGNs and astrocytes, the predominant cerebellar cell types. Because ethanol also damages the adult cerebellum, we studied the effects of chronic ethanol exposure in adult rats. One year of binge drinking did not alter L1 gene and protein expression in extracts from whole cerebellum. Thus, ethanol does not alter L1 expression in the developing or adult cerebellum; more likely, ethanol disrupts L1 function by modifying its conformation and signaling. Likewise, NAP antagonizes the actions of ethanol without altering L1 expression.