The regulation of neuronal gene expression by alcohol

Caenorhabditis elegans as an In Vivo Model Organism to Elucidate Teratogenic Effects

Exogenous teratogens contribute to approximately 10% of the human abnormality with exposure occurrence during the prenatal and fetal period. However, the assessment methods and underlying mechanism remain unclear. The nematode Caenorhabditis elegans has been recognized as one of the ideal model animals for toxicologic research as convenient culture, low cost, and complete phenotypes and genomic profiling. This chapter describes the protocols about the estimations on the teratogenic effects using nematodes as model organisms, including the growth, development, behavior, reproduction, energy balance, and transgenes.

Hippocampal ceRNA networks from chronic intermittent ethanol vapor-exposed male mice and functional analysis of top-ranked lncRNA genes for ethanol drinking phenotypes

The molecular mechanisms regulating the development and progression of alcohol use disorder (AUD) are largely unknown. While noncoding RNAs have previously been implicated as playing key roles in AUD, long-noncoding RNA (lncRNA) remains understudied in relation to AUD. In this study, we first identified ethanol-responsive lncRNAs in the mouse hippocampus that are transcriptional network hub genes. Microarray analysis of lncRNA, miRNA, circular RNA, and protein coding gene expression in the hippocampus from chronic intermittent ethanol vapor- or air- (control) exposed mice was used to identify ethanol-responsive competing endogenous RNA (ceRNA) networks. Highly interconnected lncRNAs (genes that had the strongest overall correlation to all other dysregulated genes identified) were ranked. The top four lncRNAs were novel, previously uncharacterized genes named Gm42575, 4930413E15Rik, Gm15767, and Gm33447, hereafter referred to as Pitt1, Pitt2, Pitt3, and Pitt4, respectively. We subsequently tested the hypothesis that CRISPR/Cas9 mutagenesis of the putative promoter and first exon of these lncRNAs in C57BL/6J mice would alter ethanol drinking behavior. The Drinking in the Dark (DID) assay was used to examine binge-like drinking behavior, and the Every-Other-Day Two-Bottle Choice (EOD-2BC) assay was used to examine intermittent ethanol consumption and preference. No significant differences between control and mutant mice were observed in the DID assay. Female-specific reductions in ethanol consumption were observed in the EOD-2BC assay for Pitt1, Pitt3, and Pitt4 mutant mice compared to controls. Male-specific alterations in ethanol preference were observed for Pitt1 and Pitt2. Female-specific increases in ethanol preference were observed for Pitt3 and Pitt4. Total fluid consumption was reduced in Pitt1 and Pitt2 mutants at 15% v/v ethanol and in Pitt3 and Pitt4 at 20% v/v ethanol in females only. We conclude that all lncRNAs targeted altered ethanol drinking behavior, and that lncRNAs Pitt1, Pitt3, and Pitt4 influenced ethanol consumption in a sex-specific manner. Further research is necessary to elucidate the biological mechanisms for these effects. These findings add to the literature implicating noncoding RNAs in AUD and suggest lncRNAs also play an important regulatory role in the disease.

Synaptic effects of ethanol on striatal circuitry: therapeutic implications for dystonia

Alcohol consumption affects motor behavior and motor control. Both acute and chronic alcohol abuse have been extensively investigated; however, the therapeutic efficacy of alcohol on some movement disorders, such as myoclonus-dystonia or essential tremor, still does not have a plausible mechanistic explanation. Yet, there are surprisingly few systematic trials with known GABAergic drugs mimicking the effect of alcohol on neurotransmission. In this brief survey, we aim to summarize the effects of EtOH on striatal function, providing an overview of its cellular and synaptic actions in a 'circuit-centered' view. In addition, we will review both experimental and clinical evidence, in the attempt to provide a plausible mechanistic explanation for alcohol-responsive movement disorders, with particular emphasis on dystonia. Different hypotheses emerge, which may provide a rationale for the utilization of drugs that mimic alcohol effects, predicting potential drug repositioning.

Non-coding RNA in alcohol use disorder by affecting synaptic plasticity

Alcohol use disorder (AUD) is one of the most serious public health problems worldwide. AUD is a complex disorder, and there is ample evidence that genetic predisposition is critical to its development. Recent studies have shown that genetic predisposition leads to the onset of AUD, and alcohol metabolism can affect epigenetic inheritance, which in turn affects synaptic plasticity, alters brain function, and leads to more severe addictive behaviors. Non-coding RNAs (ncRNAs), especially microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), play an important role in alcohol addiction. This paper reviews the regulatory role of ncRNAs. ncRNAs are involved in enzyme and neurotransmitter reaction systems during alcohol use disorder. Alcohol consumption regulates the expression of ncRNAs that mediate epigenetic modification and synaptic plasticity, which play an important role in the development of chronic AUD. ncRNAs may be used not only as predictors of therapeutic responses but also as therapeutic targets of AUD. Chronic alcoholism is more likely to lead to neuroimmune disorders, including permanent brain dysfunction. AUD induced by long-term alcoholism greatly alters the expression of genes in the human genome, especially the expression of ncRNAs. Alcohol can cause a series of pathological changes by interfering with gene expression, such as through disordered miRNA-mRNA expression networks, epigenetic modifications, disordered metabolism, and even synaptic remodeling. ncRNAs are involved in the transition from moderate drinking to alcohol dependence.

Chromatin-mediated alternative splicing regulates cocaine-reward behavior

Neuronal alternative splicing is a key gene regulatory mechanism in the brain. However, the spliceosome machinery is insufficient to fully specify splicing complexity. In considering the role of the epigenome in activity-dependent alternative splicing, we and others find the histone modification H3K36me3 to be a putative splicing regulator. In this study, we found that mouse cocaine self-administration caused widespread differential alternative splicing, concomitant with the enrichment of H3K36me3 at differentially spliced junctions. Importantly, only targeted epigenetic editing can distinguish between a direct role of H3K36me3 in splicing and an indirect role via regulation of splice factor expression elsewhere on the genome. We targeted Srsf11, which was both alternatively spliced and H3K36me3 enriched in the brain following cocaine self-administration. Epigenetic editing of H3K36me3 at Srsf11 was sufficient to drive its alternative splicing and enhanced cocaine self-administration, establishing the direct causal relevance of H3K36me3 to alternative splicing of Srsf11 and to reward behavior.

Chronic Ethanol Exposure Enhances Facial Stimulation-Evoked Mossy Fiber-Granule Cell Synaptic Transmission via GluN2A Receptors in the Mouse Cerebellar Cortex

Sensory information is transferred to the cerebellar cortex via the mossy fiber–granule cell (MF–GC) pathway, which participates in motor coordination and motor learning. We previously reported that chronic ethanol exposure from adolescence facilitated the sensory-evoked molecular layer interneuron–Purkinje cell synaptic transmission in adult mice in vivo. Herein, we investigated the effect of chronic ethanol exposure from adolescence on facial stimulation-evoked MF–GC synaptic transmission in the adult mouse cerebellar cortex using electrophysiological recording techniques and pharmacological methods. Chronic ethanol exposure from adolescence induced an enhancement of facial stimulation-evoked MF–GC synaptic transmission in the cerebellar cortex of adult mice. The application of an N-methyl-D-aspartate receptor (NMDAR) antagonist, D-APV (250 μM), induced stronger depression of facial stimulation-evoked MF–GC synaptic transmission in chronic ethanol-exposed mice compared with that in control mice. Chronic ethanol exposure-induced facilitation of facial stimulation evoked by MF–GC synaptic transmission was abolished by a selective GluN2A antagonist, PEAQX (10 μM), but was unaffected by the application of a selective GluN2B antagonist, TCN-237 (10 μM), or a type 1 metabotropic glutamate receptor blocker, JNJ16259685 (10 μM). These results indicate that chronic ethanol exposure from adolescence enhances facial stimulation-evoked MF–GC synaptic transmission via GluN2A, which suggests that chronic ethanol exposure from adolescence impairs the high-fidelity transmission capability of sensory information in the cerebellar cortex by enhancing the NMDAR-mediated components of MF–GC synaptic transmission in adult mice in vivo.

Moderate Ethanol Pre-treatment Mitigates ICH-Induced Injury via ER Stress Modulation in Rats

Intracerebral hemorrhage (ICH) is a life-threatening type of stroke that disrupts the normal neurological function of the brain. Clinical studies have reported a non-linear J-shaped association between alcohol consumption levels and the occurrence of cerebral stroke. Specifically, alcohol intoxication increases stroke incidence, while moderate alcohol pre-conditioning decreases stroke frequency and improves outcomes. Although alcohol pre-consumption is likely a crucial player in ICH, the underlying mechanism remains unclear. We performed 1-h alcohol pre-conditioning followed by ICH induction in Sprague-Dawley (SD) rats to investigate the role of alcohol pre-conditioning in ICH. Interestingly, behavioral test analysis found that ethanol intoxication (3 g/kg) aggravated ICH-induced neurological deficits, but moderate ethanol pre-conditioning (0.75 g/kg) ameliorated ICH-induced neurological deficits by reducing the oxidative stress and proinflammatory cytokines release. Moreover, we found that moderate ethanol pretreatment improved the striatal endoplasmic reticulum (ER) homeostasis by increasing the chaperone protein expression and reducing oxidative stress and apoptosis caused by ICH. Our findings show that the mechanism regulated by moderate ethanol pre-conditioning might be beneficial for ICH, indicating the importance of ER homeostasis, oxidative stress, and differential cytokines release in ICH.

GABAa receptor density alterations revealed in a mouse model of early moderate prenatal ethanol exposure using [18F]AH114726

INTRODUCTION

Prenatal ethanol exposure (PEE) has been shown to alter the level and function of receptors in the brain, one of which is GABA_a receptors (GABA_aR), the major inhibitory ligand gated ion channels that mediate neuronal inhibition. High dose PEE in animals resulted in the upregulation of GABA_aR, but the effects of low and moderate dose PEE at early gestation have not been investigated. This study aimed at examining GABA_aR density in the adult mouse brain following PEE during a period equivalent to the first 3 to 4 weeks in human gestation. It was hypothesized that early moderate PEE would cause alterations in brain GABA_aR levels in the adult offspring.

METHODS

C57BL/6J mice were given 10% v/v ethanol during the first 8 gestational days. Male offspring were studied using in-vivo Positron Emission Tomography (PET)/Magnetic Resonance Imaging (MRI), biodistribution, in-vitro autoradiography using [¹⁸F]AH114726, a novel flumazenil analogue with a high affinity for the benzodiazepine-binding site, and validated using immunohistochemistry.

RESULTS

In vivo PET and biodistribution did not detect alteration in brain tracer uptake. In vitro radiotracer studies detected significantly reduced GABA_aR in the olfactory bulbs. Immunohistochemistry detected reduced GABA_aR in the cerebral cortex, cerebellum and hippocampus, while Nissl staining showed that cell density was significantly higher in the striatum following PEE.

CONCLUSION

Early moderate PEE may induce long-term alterations in the GABA_aR system that persisted into adulthood.

Integrative In Silico and In Vitro Transcriptomics Analysis Revealed Gene Expression Changes and Oncogenic Features of Normal Cholangiocytes after Chronic Alcohol Exposure

Cholangiocarcinoma (CCA) is a malignant tumor originating from cholangiocyte. Prolonged alcohol consumption has been suggested as a possible risk factor for CCA, but there is no information about alcohol’s mechanisms in cholangiocyte. This study was designed to investigate global transcriptional alterations through RNA-sequencing by using chronic alcohol exposure (20 mM for 2 months) in normal human cholangiocyte MMNK-1 cells. To observe the association of alcohol induced CCA pathogenesis, we combined differentially expressed genes (DEGs) with computational bioinformatics of CCA by using publicly gene expression omnibus (GEO) datasets. For biological function analysis, Gene ontology (GO) analysis showed biological process and molecular function related to regulation of transcription from RNA polymerase II promoter, while cellular component linked to the nucleoplasm. KEGG pathway presented pathways in cancer that were significantly enriched. From KEGG result, we further examined the oncogenic features resulting in chronic alcohol exposure, enhanced proliferation, and migration through CCND-1 and MMP-2 up-regulation, respectively. Finally, combined DEGs were validated in clinical data including TCGA and immunohistochemistry from HPA database, demonstrating that FOS up-regulation was related to CCA pathogenesis. This study is the first providing more information and molecular mechanisms about global transcriptome alterations and oncogenic enhancement of chronic alcohol exposure in normal cholangiocytes.

Alcohol protects the CNS by activating HSF1 and inducing the heat shock proteins

Although alcohol abuse and dependence have profound negative health consequences, emerging evidence suggests that exposure to low/moderate concentrations of ethanol protects multiple organs and systems. In the CNS, moderate drinking decreases the risk of dementia and Alzheimer's disease. This neuroprotection correlates with an increased expression of the heat shock proteins (HSPs). Multiple epidemiological studies revealed an inverse association between ethanol intoxication and traumatic brain injury mortality. In this case, ethanol-induced HSPs limit the inflammatory immune response diminishing cell death and improving the neurobehavioural outcome. Ethanol also protects the brain against ischemic injuries via the HSPs. In our laboratory, we demonstrated that ethanol increased the expression of several HSP genes in neurons and astrocytes by activating the transcription factor, heat shock factor 1 (HSF1). HSF1 induces HSPs that target misfolded proteins for refolding or degradation, increasing the survival chances of the cells. These data indicate that ethanol neuroprotection is mediated by the activation HSF1 and the induction of HSPs.

How alcohol drinking affects our genes: an epigenetic point of view

This work highlights recent studies in epigenetic mechanisms that play a role in alcoholism, which is a complex multifactorial disorder. There is a large body of evidence showing that alcohol can modify gene expression through epigenetic processes, namely DNA methylation and nucleosomal remodeling via histone modifications. In that regard, chronic exposure to ethanol modifies DNA and histone methylation, histone acetylation, and microRNA expression. The alcohol-mediated chromatin remodeling in the brain promotes the transition from use to abuse and addiction. Unravelling the multiplex pattern of molecular modifications induced by ethanol could support the development of new therapies for alcoholism and drug addiction targeting epigenetic processes.

Predictors of alcohol responsiveness in dystonia

OBJECTIVE

To determine predictors of alcohol responsiveness in a large cohort of patients with dystonia.

METHODS

A total of 2,159 participants with dystonia were prospectively enrolled in the cross-sectional Dystonia Coalition multicenter study. Patients with secondary, combined, or confirmed genetic dystonia (total n = 164) or unknown alcohol responsiveness (n = 737) were excluded. Patients answered a standardized questionnaire and were clinically examined using a standardized video protocol and the Burke-Fahn-Marsden Dystonia Rating Scale. Alcohol responsiveness was determined by patients' self-report.

RESULTS

A total of 1,258 patients with isolated dystonia (mean age: 59.5 ± 12.2 years; 898 women) met the inclusion criteria; 369 patients (29.3%) reported improvement of dystonia after alcohol consumption. Alcohol responsiveness was not related to sex (p = 0.742), age (p = 0.715), or severity of dystonia (p = 0.623). Age at onset was lower in patients who responded to alcohol (p < 0.001). Alcohol responsiveness differed across dystonia subgroups (multifocal/generalized > segmental [p = 0.014]; cervical and laryngeal > cranial and limb [p < 0.001]) and was related to a positive family history of movement disorders (p = 0.001), and presence of tremor (p < 0.001).

CONCLUSION

The association of alcohol responsiveness with a positive family history for movement disorders, generalized dystonia, and an earlier age at onset suggests that patients with dystonia who have an underlying genetic contribution may be more likely to respond beneficially to alcohol. The fact that dystonic tremor may respond to alcohol is in keeping with the observation that the intake of GABAergic drugs may have a beneficial effect in a proportion of patients.

Role of GABAA receptors in alcohol use disorders suggested by chronic intermittent ethanol (CIE) rodent model

GABAergic inhibitory transmission is involved in the acute and chronic effects of ethanol on the brain and behavior. One-dose ethanol exposure induces transient plastic changes in GABAA receptor subunit levels, composition, and regional and subcellular localization. Rapid down-regulation of early responder δ subunit-containing GABAA receptor subtypes mediating ethanol-sensitive tonic inhibitory currents in critical neuronal circuits corresponds to rapid tolerance to ethanol's behavioral responses. Slightly slower, α1 subunit-containing GABAA receptor subtypes mediating ethanol-insensitive synaptic inhibition are down-regulated, corresponding to tolerance to additional ethanol behaviors plus cross-tolerance to other GABAergic drugs including benzodiazepines, anesthetics, and neurosteroids, especially sedative-hypnotic effects. Compensatory up-regulation of synaptically localized α4 and α2 subunit-containing GABAA receptor subtypes, mediating ethanol-sensitive synaptic inhibitory currents follow, but exhibit altered physio-pharmacology, seizure susceptibility, hyperexcitability, anxiety, and tolerance to GABAergic positive allosteric modulators, corresponding to heightened alcohol withdrawal syndrome. All these changes (behavioral, physiological, and biochemical) induced by ethanol administration are transient and return to normal in a few days. After chronic intermittent ethanol (CIE) treatment the same changes are observed but they become persistent after 30 or more doses, lasting for at least 120 days in the rat, and probably for life. We conclude that the ethanol-induced changes in GABAA receptors represent aberrant plasticity contributing critically to ethanol dependence and increased voluntary consumption. We suggest that the craving, drug-seeking, and increased consumption in the rat model are tied to ethanol-induced plastic changes in GABAA receptors, importantly the development of ethanol-sensitive synaptic GABAA receptor-mediating inhibitory currents that participate in maintained positive reward actions of ethanol on critical neuronal circuits. These probably disinhibit nerve endings of inhibitory GABAergic neurons on dopamine reward circuit cells, and limbic system circuits mediating anxiolysis in hippocampus and amygdala. We further suggest that the GABAA receptors contributing to alcohol dependence in the rat and presumably in human alcohol use disorders (AUD) are the ethanol-induced up-regulated subtypes containing α4 and most importantly α2 subunits. These mediate critical aspects of the positive reinforcement of ethanol in the dependent chronic user while alleviating heightened withdrawal symptoms experienced whenever ethanol is absent. The speculative conclusions based on firm observations are readily testable.

By up-regulating μ- and δ-opioid receptors, neuron-restrictive silencer factor knockdown promotes neurological recovery after ischemia

We investigated the effects of neuron-restrictive silencer factor (NRSF) on proliferation of endogenous nerve stem cells (NSCs) and on μ- and δ-opioid receptor (MOR/DOR) expression in rats after cerebral ischemia. Among 100 rats subjected to cerebral ischemia, 20 rats were transfected with NRSF shRNA, and the remaining 80 were randomly assigned to normal, sham, model, and negative control (NC) groups. On days 7, 14, and 28 after ischemia and reperfusion, neurological function scores were assigned and a step-down passive avoidance test was conducted. Nerve function scores, step-down reaction periods, error times and apoptosis rates, as well as levels of B-cell CLL/lymphoma 2 (Bcl-2), BCL2-associated X protein (Bax), and NRSF expression were lower in the NRSF shRNA group than in the model and NC groups. By contrast, step-down latency, numbers of bromodeoxyuridine-positive cells, MOR/DOR expression, and phosphorylation of extracellular signal regulated protein kinase (ERK) and cAMP response element binding protein (CREB) were higher in the NRSF shRNA group than in the model and NC groups. These results suggest that by up-regulating MOR/DOR expression, NRSF knockdown accelerates recovery of neurological function after cerebral ischemia, at least in part by promoting NSC proliferation and inhibiting apoptosis.

Ethanol Modulates the Spontaneous Complex Spike Waveform of Cerebellar Purkinje Cells Recorded in vivo in Mice

Cerebellar Purkinje cells (PCs) are sensitive to ethanol, but the effect of ethanol on spontaneous complex spike (CS) activity in these cells in vivo is currently unknown. Here, we investigated the effect of ethanol on spontaneous CS activity in PCs in urethane-anesthetized mice using in vivo patch-clamp recordings and pharmacological manipulation. Ethanol (300 mM) induced a decrease in the CS-evoked pause in simple spike (SS) firing and in the amplitude of the afterhyperpolarization (AHP) under current clamp conditions. Under voltage-clamp conditions, ethanol significantly decreased the area under the curve (AUC) and the number of CS spikelets, without changing the spontaneous frequency of the CSs or the instantaneous frequency of the CS spikelets. Ethanol-induced a decrease in the AUC of spontaneous CSs was concentration dependent. The EC₅₀ of ethanol for decreasing the AUC of spontaneous CSs was 168.5 mM. Blocking N-methyl-D-aspartate receptors (NMDARs) failed to prevent the ethanol-induced decreases in the CS waveform parameters. However, blockade of cannabinoid receptor 1 (CB1) significantly suppressed the ethanol-induced effects on the CS-evoked pause in SS firing, amplitude of the AHP, spikelet number and the AUC of CSs. Moreover, a CB1 receptor agonist not only reduced the number of spikelets and the AUC of CSs, but also prevented the ethanol-induced inhibition of CS activity. Our results indicate that ethanol inhibits CS activity via activation of the CB1 receptor in vivo in mice, suggesting that excessive ethanol intake inhibits climbing fiber (CF)–PC synaptic transmission by modulating CB1 receptors in the cerebellar cortex.

Assessment of Expression of Genes Coding GABAA Receptors during Chronic and Acute Intoxication of Laboratory Rats with Ethanol

Expression of genes encoding the individual subunits of ionotropic GABAA receptor was assessed after acute and chronic intoxication of rats with ethanol. The chronic 1-month-long exposure to ethanol signifi cantly decreased (by 38%) expression of Gabrb1 gene in the hippocampus. Acute exposure to ethanol elevated expression of genes Gabrb1 (by 1.7 times), Gabra1 (by 3.8 times), and Gabra4 (by 6.5 times), although it diminished expression of Gabra2 gene by 1.4 times. In preliminarily alcoholized rats, acute intoxication with ethanol enhanced expression of genes Gabrb1 and Gabra5 by 1.7 and 8.7 times, respectively. There was neither acute nor chronic effect of ethanol on expression of gene Gabra3.

Alcohol consumption induces global gene expression changes in VTA dopaminergic neurons

Alcoholism is associated with dysregulation in the neural circuitry that mediates motivated and goal-directed behaviors. The dopaminergic (DA) connection between the ventral tegmental area (VTA) and the nucleus accumbens is viewed as a critical component of the neurocircuitry mediating alcohol's rewarding and behavioral effects. We sought to determine the effects of binge alcohol drinking on global gene expression in VTA DA neurons. Alcohol-preferring C57BL/6J × FVB/NJ F1 hybrid female mice were exposed to a modified drinking in the dark (DID) procedure for 3 weeks, while control animals had access to water only. Global gene expression of laser-captured tyrosine hydroxylase (TH)-positive VTA DA neurons was measured using microarrays. A total of 644 transcripts were differentially expressed between the drinking and nondrinking mice, and 930 transcripts correlated with alcohol intake during the last 2 days of drinking in the alcohol group. Bioinformatics analysis of alcohol-responsive genes identified molecular pathways and networks perturbed in DA neurons by alcohol consumption, which included neuroimmune and epigenetic functions, alcohol metabolism and brain disorders. The majority of genes with high and specific expression in DA neurons were downregulated by or negatively correlated with alcohol consumption, suggesting a decreased activity of DA neurons in high drinking animals. These changes in the DA transcriptome provide a foundation for alcohol-induced neuroadaptations that may play a crucial role in the transition to addiction.

Apoptosis of Purkinje and granular cells of the cerebellum following chronic ethanol intake

Ethanol alters motricity, learning, cognition, and cellular metabolism in the cerebellum. We evaluated the effect of ethanol on apoptosis in Golgi, Purkinje, and granule cells of the cerebellum in adult rats. There were two groups of 20 rats: a control group that did not consume ethanol and an experimental group of UChA rats that consumed ethanol at 10% (<2 g ethanol/kg body weight/day). At 120 days old, rats were anesthetized and decapitated, and their cerebella were collected and fixed. Cerebellar sections were subjected to immunohistochemistry for terminal deoxynucleotide transferase dUTP nick end labeling (TUNEL), caspase-3, X-linked inhibitor of apoptosis protein (XIAP), and insulin-like growth factor 1-receptor (IGF-1R); real-time PCR (RT-PCR) to determine caspase-3, XIAP, and IGF-1R gene expression; and transmission electron microscopy (TEM). We identified fragmentation of DNA and an increase in caspase-3 protein and XIAP in Purkinje cells, whereas granule cells exhibited increased caspase-3 and XIAP. IGF-1R expression was unchanged. There was no significant difference in gene expression of caspase-3, XIAP, and IGF-1R. There were an increase in lipid droplets, a reduction in the cellular cytoplasm in electron-dense nuclei, and changes in the myelin sheath in the cerebellar cortex. In conclusion, our data demonstrated that ethanol induced apoptosis in the Purkinje and granule cells of the cerebellum of adult UChA rats.

Alcoholics have more tryptophan hydroxylase 2 mRNA and protein in the dorsal and median raphe nuclei

BACKGROUND

Chronic alcohol use depletes brain serotonin (5-hydroxytryptamine [5-HT]), yet we previously found more tryptophan hydroxylase 2 (TPH2), the rate-limiting biosynthetic enzyme for 5-HT, in the dorsal raphe nucleus (DRN) of alcoholics. We sought to determine whether the increase in amount of TPH2 enzyme is associated with more TPH2 mRNA gene expression in the DRN of a new cohort of alcoholics and controls.

METHODS

TPH2 mRNA and protein were measured by in situ hybridization and immunoautoradiography, respectively, in the DRN and median raphe nucleus (MRN) of age- and sex-matched pairs (n = 16) of alcoholics and nonpsychiatric controls. Alcohol use disorder diagnosis and medical, psychiatric, and family histories were obtained by psychological autopsy. Age and sex were covariates in the analyses.

RESULTS

TPH2 mRNA in alcoholics was greater in the DRN and MRN compared to controls (DRN: controls: 3.6 ± 1.6, alcoholics: 4.8 ± 1.8 nCi/mg of tissue, F = 4.106, p = 0.02; MRN: controls: 2.6 ± 1.2, alcoholics: 3.5 ± 1.1 nCi/mg of tissue, F = 3.96, p = 0.024). The difference in TPH2 mRNA was present in all DRN subnuclei (dorsal [DRd]: 135%, interfascicular [DRif]: 139%, ventral [DRv]: 135%, ventrolateral [DRvl]: 136% of control p < 0.05) except the caudal subnucleus. Alcoholics also had more TPH2 protein in the DRN and MRN than controls (DRN: controls: 265 ± 47, alcoholics: 318 ± 47 μCi/g, F = 8.72, p = 0.001; MRN: controls: 250 ± 33, alcoholics: 345 ± 39 μCi/g, F = 7.78, p = 0.001). There is a positive correlation between TPH2 protein and mRNA expression in the DRN (r = 0.815, p < 0.001), suggesting that the higher amount of TPH2 protein is due to an increase in TPH2 gene expression.

CONCLUSIONS

These findings suggest that greater TPH2 gene expression is the basis for more TPH2 protein in the DRN and MRN in alcoholics.

Impaired one carbon metabolism and DNA methylation in alcohol toxicity

Excessive alcohol consumption is a prominent problem and one of the major causes of mortality and morbidity around the world. Long-term, heavy alcohol consumption is associated with a number of deleterious health consequences, such as cancer, heart and liver disease, a variety of neurological, cognitive, and behavioral deficits. Alcohol consumption is also associated with developmental defects. The causes of alcohol-induced toxicity are presently unclear. One of the mechanisms underlying alcohol toxicity has to do with its interaction with folic acid/homocysteine or one-carbon metabolism (OCM). OCM is a major donor of methyl groups for methylation, particularly DNA methylation critical for epigenetic regulation of gene expression, and its disturbance may compromise DNA methylation, thereby affecting gene expression. OCM disturbance mediated by nutrient deficits is a well-known risk factor for various disorders and developmental defects (e.g., neural tube defects). In this review, we summarize the role of OCM disturbance and associated epigenetic aberrations in chronic alcohol-induced toxicity. In this review, we summarize the role of one-carbon metabolism (OCM) aberrations in chronic alcohol-induced toxicity. OCM is a major donor of methyl groups for methylation reactions, particularly DNA methylation critical for epigenetic regulation of gene expression. Alcohol interference with OCM and consequent reduced availability of methyl groups, improper DNA methylation, and aberrant gene expression can play a causative role in alcohol toxicity.

Converging actions of alcohol on liver and brain immune signaling

Chronic excessive alcohol consumption results in inflammation in multiple organs, including the brain. While the contribution of neuroinflammation to alcohol-related cognitive dysfunction and behavioral alterations is established, the mechanisms by which alcohol triggers inflammation in the brain are only partially understood. There are acute and long-term alterations in brain function due to intercellular and intracellular changes of different cell types as a result of alcohol consumption. This review focuses on the alcohol-induced proinflammatory cellular and molecular changes in the central nervous system. Alcohol passes through the blood-brain barrier and alters neurotransmission. Alcohol use activates microglia and astrocyte, contributing to neurodegeneration and impaired regeneration. Alcohol-induced cell injury in the brain results in release of damage-associated molecular patterns, such as high mobility group box 1, that trigger inflammatory changes through activation of pattern recognition receptors. In addition, alcohol consumption increases intestinal permeability and results in increased levels of pathogen-associated molecular pattern such as endotoxin in the systemic circulation that triggers PRRs and inflammation. The Toll-like receptor-4 pathway that activates nuclear factor-κB and secretion of proinflammatory cytokines, tumor necrosis factor-α, interleukin-1-beta, and chemokines, including monocyte chemotactic protein-1, has been suggested to contribute to alcohol-induced neuroinflammation. Alcohol-induced IL-1β secretion also requires Nod-like receptor-mediated inflammasome and caspase-1 activation, and, consistent with this, disruption of IL-1/IL-1-receptor signaling prevents alcohol-induced neuroinflammation. Delicate regulators of inflammatory gene expressions are micro-RNAs (miRs) that have recently been identified in alcohol-related neuroinflammation. Alcohol induces miR155, a regulator of inflammation in the brain, and deficiency in miR-155 in mice was protective from neuroinflammatory changes. These observations suggest that manipulation of miR pathways and cytokine induction may reduce alcohol-induced proinflammatory processes.

Molecular basis of alcoholism

Acute alcohol intoxication causes cellular changes in the brain that last for hours, while chronic alcohol use induces widespread neuroadaptations in the nervous system that can last a lifetime. Chronic alcohol use and the progression into dependence involve the remodeling of synapses caused by changes in gene expression produced by alcohol. The progression of alcohol use, abuse, and dependence can be divided into stages, which include intoxication, withdrawal, and craving. Each stage is associated with specific changes in gene expression, cellular function, brain circuits, and ultimately behavior. What are the molecular mechanisms underlying the transition from recreational use (acute) to dependence (chronic)? What cellular adaptations result in drug memory retention, leading to the persistence of addictive behaviors, even after prolonged drug abstinence? Research into the neurobiology of alcoholism aims to answer these questions. This chapter will describe the molecular adaptations caused by alcohol use and dependence, and will outline key neurochemical participants in alcoholism at the molecular level, which are also potential targets for therapy.

Neuroimmune pathways in alcohol consumption: evidence from behavioral and genetic studies in rodents and humans

Immune or brain proinflammatory signaling has been linked to some of the behavioral effects of alcohol. Immune signaling appears to regulate voluntary ethanol intake in rodent models, and ethanol intake activates the immune system in multiple models. This bidirectional link raises the possibility that consumption increases immune signaling, which in turn further increases consumption in a feed-forward cycle. Data from animal and human studies provide overlapping support for the involvement of immune-related genes and proteins in alcohol action, and combining animal and human data is a promising approach to systematically evaluate and nominate relevant pathways. Based on rodent models, neuroimmune pathways may represent unexplored, nontraditional targets for medication development to reduce alcohol consumption and prevent relapse. Peroxisome proliferator-activated receptor agonists are one class of anti-inflammatory medications that demonstrate antiaddictive properties for alcohol and other drugs of abuse. Expression of immune-related genes is altered in animals and humans following chronic alcohol exposure, and the regulatory influences of specific mRNAs, microRNAs, and activated cell types are areas of intense study. Ultimately, the use of multiple datasets combined with behavioral validation will be needed to link specific neuroimmune pathways to addiction vulnerability.

Positively correlated miRNA-mRNA regulatory networks in mouse frontal cortex during early stages of alcohol dependence

Background

Although the study of gene regulation via the action of specific microRNAs (miRNAs) has experienced a boom in recent years, the analysis of genome-wide interaction networks among miRNAs and respective targeted mRNAs has lagged behind. MicroRNAs simultaneously target many transcripts and fine-tune the expression of genes through cooperative/combinatorial targeting. Therefore, they have a large regulatory potential that could widely impact development and progression of diseases, as well as contribute unpredicted collateral effects due to their natural, pathophysiological, or treatment-induced modulation. We support the viewpoint that whole mirnome-transcriptome interaction analysis is required to better understand the mechanisms and potential consequences of miRNA regulation and/or deregulation in relevant biological models. In this study, we tested the hypotheses that ethanol consumption induces changes in miRNA-mRNA interaction networks in the mouse frontal cortex and that some of the changes observed in the mouse are equivalent to changes in similar brain regions from human alcoholics.

Results

miRNA-mRNA interaction networks responding to ethanol insult were identified by differential expression analysis and weighted gene coexpression network analysis (WGCNA). Important pathways (coexpressed modular networks detected by WGCNA) and hub genes central to the neuronal response to ethanol are highlighted, as well as key miRNAs that regulate these processes and therefore represent potential therapeutic targets for treating alcohol addiction. Importantly, we discovered a conserved signature of changing miRNAs between ethanol-treated mice and human alcoholics, which provides a valuable tool for future biomarker/diagnostic studies in humans. We report positively correlated miRNA-mRNA expression networks that suggest an adaptive, targeted miRNA response due to binge ethanol drinking.

Conclusions

This study provides new evidence for the role of miRNA regulation in brain homeostasis and sheds new light on current understanding of the development of alcohol dependence. To our knowledge this is the first report that activated expression of miRNAs correlates with activated expression of mRNAs rather than with mRNA downregulation in an in vivo model. We speculate that early activation of miRNAs designed to limit the effects of alcohol-induced genes may be an essential adaptive response during disease progression.

Altered GABAA receptor expression and seizure threshold following acute ethanol challenge in mice lacking the RIIβ subunit of PKA

Ethanol causes pathological changes in GABAA receptor trafficking and function. These changes are mediated in part by ethanol activation of protein kinase A (PKA). The current study investigated the expression of the GABAA α1 and α4 subunits and the kinase anchoring protein AKAP150, as well as bicuculline-induced seizure threshold, at baseline and following acute injection of ethanol (3.5 g/kg IP) in a mouse line lacking the regulatory RIIβ subunit of PKA. Whole cerebral cortices were harvested at baseline, 1 h, or 46 h following injection of ethanol or saline and subjected to fractionation and western blot analysis. Knockout (RIIβ-/-) mice had similar baseline levels of PKA RIIα and GABAA α1 and α4 subunits compared to wild type (RIIβ+/+) littermates, but had deficits in AKAP150. GABAA α1 subunit levels were decreased in the P2 fraction of RIIβ-/-, but not RIIβ+/+, mice following 1 h ethanol, an effect that was driven by decreased α1 expression in the synaptic fraction. GABAA α4 subunits in the P2 fraction were not affected by 1 h ethanol; however, synaptic α4 subunit expression was increased in RIIβ+/+, but not RIIβ-/- mice, while extrasynaptic α4 and δ subunit expression were decreased in RIIβ-/-, but not RIIβ+/+ mice. Finally, RIIβ knockout was protective against bicuculline-induced seizure susceptibility. Overall, the results suggest that PKA has differential roles in regulating GABAA receptor subunits. PKA may protect against ethanol-induced deficits in synaptic α1 and extrasynaptic α4 receptors, but may facilitate the increase of synaptic α4 receptors.

Alcohol and NMDA receptor: current research and future direction

The brain is one of the major targets of alcohol actions. Most of the excitatory synaptic transmission in the central nervous system is mediated by N-methyl-D-aspartate (NMDA) receptors. However, one of the most devastating effects of alcohol leads to brain shrinkage, loss of nerve cells at specific regions through a mechanism involving excitotoxicity, oxidative stress. Earlier studies have indicated that chronic exposure to ethanol both in vivo and in vitro, increases NR1 and NR2B gene expression and their polypeptide levels. The effect of alcohol and molecular changes on the regulatory process, which modulates NMDAR functions including factors altering transcription, translation, post-translational modifications, and protein expression, as well as those influencing their interactions with different regulatory proteins (downstream effectors) are incessantly increasing at the cellular level. Further, I discuss the various genetically altered mice approaches that have been used to study NMDA receptor subunits and their functional implication. In a recent countable review, epigenetic dimension (i.e., histone modification-induced chromatin remodeling and DNA methylation, in the process of alcohol related neuroadaptation) is one of the key molecular mechanisms in alcohol mediated NMDAR alteration. Here, I provide a recount on what has already been achieved, current trends and how the future research/studies of the NMDA receptor might lead to even greater engagement with many possible new insights into the neurobiology and treatment of alcoholism.

Chronic ethanol exposure increases cytochrome P-450 and decreases activated in blocked unfolded protein response gene family transcripts in caenorhabditis elegans

Ethanol is a widely consumed and rapidly absorbed toxin. While the physiological effects of ethanol consumption are well known, the underlying biochemical and molecular changes at the gene expression level in whole animals remain obscure. We exposed the model organism Caenorhabditis elegans to 0.2 M ethanol from the embryo to L4 larva stage and assayed gene expression changes in whole animals using RNA-Seq and quantitative real-time PCR. We observed gene expression changes in 1122 genes (411 up, 711 down). Cytochrome P-450 (CYP) gene family members (12 of 78) were upregulated, whereas activated in blocked unfolded protein response (ABU) (7 of 15) were downregulated. Other detoxification gene family members were also regulated including four glutathione-S-transferases and three flavin monooxygenases. The results presented show specific gene expression changes following chronic ethanol exposure in C. elegans that indicate both persistent upregulation of detoxification response genes and downregulation of endoplasmic reticulum stress pathway genes.

Intergenerational health responses to adverse and enriched environments

Health consequences of relative or absolute poverty constitute a definitive area of study in social medicine. As demonstrated in the extreme example of the Dutch Hunger Winter from 1944 to 1945, prenatal hunger can lead to adult schizophrenia and depression. A Norwegian study showed how childhood poverty resulted in a heightened risk of myocardial infarction in adulthood. In England, a study of extended impaired prenatal nutrition indicated three different types of increased cardiovascular risk at older ages. Current animal and human studies link both adverse and enriched environmental exposures to intergenerational transmission. We do not fully understand the molecular mechanisms for it; however, studies that follow up epigenetic marks within a generation combined with exploration of gametic epigenetic inheritance may help explain the prevalence of certain conditions such as cardiovascular disease, schizophrenia, and alcoholism, which have complex etiologies. Insights from these studies will be of great public health importance.

Gene Expression Under the Influence: Transcriptional Profiling of Ethanol in the Brain

Sensitivity to ethanol intoxication, propensity to drink ethanol and vulnerability to develop alcoholism are all influenced by genetic factors. Conversely, exposure to ethanol or subsequent withdrawal produce gene expression changes, which, in combination with environmental variables, may participate in the emergence of compulsive drinking and relapse. The present review offers an integrated perspective on brain gene expression profiling in rodent models of predisposition to differential ethanol sensitivity or consumption, in rats and mice subjected to acute or chronic ethanol exposure, as well as in human alcoholics. The functional categories over-represented among differentially expressed genes suggest that the transcriptional effects of chronic ethanol consumption contribute to the neuroplasticity and neurotoxicity characteristic of alcoholism. Importantly, ethanol produces distinct transcriptional changes within the different brain regions involved in intoxication, reinforcement and addiction. Special emphasis is put on recent profiling studies that have provided some insights into the molecular mechanisms potentially mediating genome-wide regulation of gene expression by ethanol. In particular, current evidence for a role of transcription factors, chromatin remodeling and microRNAs in coordinating the expression of large sets of genes in animals predisposed to excessive ethanol drinking or exposed to protracted abstinence, as well as in human alcoholics, is presented. Finally, studies that have compared ethanol with other drugs of abuse have highlighted common gene expression patterns that may play a central role in drug addiction. The availability of novel technologies and a focus on mechanistic approaches are shaping the future of ethanol transcriptomics.

Pharmacologic manipulation of conventional outflow facility in ex vivo mouse eyes

PURPOSE

Mouse models are useful for glaucoma research, but it is unclear whether intraocular pressure (IOP) regulation in mice operates through mechanisms similar to those in humans. Our goal was to determine whether pharmacologic compounds that affect conventional outflow facility in human eyes exert similar effects in C57BL/6 mice.

METHODS

A computerized perfusion system was used to measure conventional outflow facility in enucleated mouse eyes ex vivo. Paired eyes were perfused sequentially, either immediately after enucleation or after 3 hours storage at 4°C. Three groups of experiments examined sphingosine 1-phosphate (S1P), S1P with antagonists to S1P(1) and S1P(2) receptors, and the prostanoid EP(4) receptor agonist 3,7-dithia PGE(1). We also examined whether a 24-hour postmortem delay affected the response to 3,7-dithia prostaglandin E(1) (PGE(1)).

RESULTS

S1P decreased facility by 39%, and was blocked almost completely by an S1P(2), but not S1P(1), receptor antagonist. The S1P(2) receptor antagonist alone increased facility nearly 2-fold. 3,7-dithia PGE(1) increased facility by 106% within 3 hours postmortem. By 24 hours postmortem, the facility increase caused by 3,7-dithia PGE(1) was reduced 3-fold, yet remained statistically detectable.

CONCLUSIONS

C57BL/6 mice showed opposing effects of S1P(2) and EP(4) receptor activation on conventional outflow facility, as observed in human eyes. Pharmacologic effects on facility were detectable up to 24 hours postmortem in enucleated mouse eyes. Mice are suitable models to examine the pharmacology of S1P and EP(4) receptor stimulation on IOP regulation as occurs within the conventional outflow pathway of human eyes, and are promising for studying other aspects of aqueous outflow dynamics.

Epigenetics-beyond the genome in alcoholism

Genetic and environmental factors play a role in the development of alcoholism. Whole-genome expression profiling has highlighted the importance of several genes that may contribute to alcohol abuse disorders. In addition, more recent findings have added yet another layer of complexity to the overall molecular mechanisms involved in a predisposition to alcoholism and addiction by demonstrating that processes related to genetic factors that do not manifest as DNA sequence changes (i.e., epigenetic processes) play a role. Both acute and chronic ethanol exposure can alter gene expression levels in specific neuronal circuits that govern the behavioral consequences related to tolerance and dependence. The unremitting cycle of alcohol consumption often includes satiation and self-medication with alcohol, followed by excruciating withdrawal symptoms and the resultant relapse, which reflects both the positive and negative affective states of alcohol addiction. Recent studies have indicated that behavioral changes induced by acute and chronic ethanol exposure may involve chromatin remodeling resulting from covalent histone modifications and DNA methylation in the neuronal circuits involving a brain region called the amygdala. These findings have helped identify enzymes involved in epigenetic mechanisms, such as the histone deacetylase, histone acetyltransferase, and DNA methyltransferase enzymes, as novel therapeutic targets for the development of future pharmacotherapies for the treatment of alcoholism.

A study on the influence of ethanol over the primary cultured rat cortical neurons by using the scanning electron microscopy

As an inhibitor and toxic factor of central nervous system, ethanol inhibits the action of the neurons and causes various kinds of neuronal damage. However, the precise mechanisms that ethanol-induced neuronal damage in the central nervous system remain unclear. In spite of thousands of published studies, little information is available on the neurons' morphological alteration in the central nervous system. In this study, we investigated the morphological alterations of the primary cultured rat cortical neurons after they were treated by different concentrations of ethanol using the scanning electron microscopy. Our results showed that the moderate or high concentration of ethanol could lead to morphological changes of these cultured rat cortical neurons, and they were closely associated with the duration of time. Our study will provide a new base for further studies on the effects of ethanol in the central nervous system.

Up-regulation of microRNAs in brain of human alcoholics

BACKGROUND

MicroRNAs (miRNAs) are small, noncoding oligonucleotides with an important role in posttranscriptional regulation of gene expression at the level of translation and mRNA degradation. Recent studies have revealed that miRNAs play important roles in a variety of biological processes, such as cell proliferation, neuronal differentiation, developmental timing, synapse function, and neurogenesis. A single miRNA can target hundreds of mRNA transcripts for either translation repression or degradation, but the function of many human miRNAs is not known.

METHODS

miRNA array analysis was performed on the prefrontal cortex of 27 individual human cases (14 alcoholics and 13 matched controls). Target genes for differentially expressed miRNAs were predicted using multiple target prediction algorithms and a consensus approach, and predicted targets were matched against differentially expressed mRNAs from the same samples. Over- and under-representation analysis was performed using hypergeometric probability and z-score tests.

RESULTS

Approximately 35 miRNAs were significantly up-regulated in the alcoholic group compared with controls. Target prediction showed a large degree of overlap with our published cDNA microarray data. Functional classification of the predicted target genes of the regulated miRNAs includes apoptosis, cell cycle, cell adhesion, nervous system development, and cell-cell signaling.

CONCLUSIONS

These data suggest that the reduced expression of genes in human alcoholic cases may be because of the up-regulated miRNAs. Cellular processes fundamental to neuronal plasticity appear to represent major targets of the suggested miRNA regulation.

Differential expression of 14-3-3 isoforms in human alcoholic brain

BACKGROUND

Neuropathological damage as a result of chronic alcohol abuse often results in the impairment of cognitive function. The damage is particularly marked in the frontal cortex. The 14-3-3 protein family consists of 7 proteins, β, γ, ε, ζ, η, θ, and σ, encoded by 7 distinct genes. They are highly conserved molecular chaperones with roles in the regulation of metabolism, signal transduction, cell-cycle control, protein trafficking, and apoptosis. They may also play an important role in neurodegeneration in chronic alcoholism.

METHODS

We used real-time PCR to measure the expression of 14-3-3 mRNA transcripts in both the dorsolateral prefrontal cortex and motor cortex of human brains obtained at autopsy.

RESULTS

We found significantly lower 14-3-3β, γ, and θ expression in both cortical areas of alcoholics, but no difference in 14-3-3η expression, and higher expression of 14-3-3σ in both areas. Levels of 14-3-3ζ and ε transcripts were significantly lower only in alcoholic motor cortex.

CONCLUSIONS

Altered 14-3-3 expression could contribute to synaptic dysfunction and altered neurotransmission in chronic alcohol misuse by human subjects.

Drinking pattern and socio-cultural aspects on immune response: an overview

Social acceptance of drinking involves social and cultural roles and has important implications for public health. Since extensive evidence indicates that alcohol possesses immunomodulatory properties, scientists have recently debated the influence of alcohol consumption on the immune response, particularly in countries where drinking in a social setting is a part of cultural identity. Experimental and clinical data support the conclusion that alcohol is a potent immunomodulator. While high alcohol consumption suppresses a wide range of immune responses, leading to an increased incidence of a number of infectious diseases, moderate alcohol consumption may have a beneficial impact on the immune system, compared to alcohol abuse or abstinence, most likely due to the multiple components of polyphenol-rich alcoholic contributing to the protective effect seen for moderate alcohol consumption on CVD and the immune system. Despite this, the scientific literature appears to be concerned about the diseases associated with excessive drinking in some societies and cultures. Thus, the present review recognizes the importance to consider social and cultural aspects of drinking when examining the whole dimension of alcohol consumption (amount, beverage type, frequency and variability), in order to estimate global risk of consequences on host defence to better understand alcohol-related harm or benefit.