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

Independent and Combined Effects of Prenatal Alcohol Exposure and Prenatal Stress on Fetal HPA Axis Development

Prenatal alcohol exposure (PAE) and prenatal stress (PS) are highly prevalent conditions known to affect fetal programming of the hypothalamic-pituitary-adrenal (HPA) axis. The objectives of this study were to assess the effect of light PAE, PS, and PAE-PS interaction on fetal HPA axis activity assessed via placental and umbilical cord blood biomarkers. Participants of the ENRICH-2 cohort were recruited during the second trimester and classified into the PAE and unexposed control groups. PS was assessed by the Perceived Stress Scale. Placental tissue was collected promptly after delivery; gene and protein analysis for 11β-HSD1, 11β-HSD2, and pCRH were conducted by qPCR and ELISA, respectively. Umbilical cord blood was analyzed for cortisone and cortisol. Pearson correlation and multivariable linear regression examined the association of PAE and PS with HPA axis biomarkers. Mean alcohol consumption in the PAE group was ~2 drinks/week. Higher PS was observed in the PAE group (p < 0.01). In multivariable modeling, PS was associated with pCRH gene expression (β = 0.006, p < 0.01), while PAE was associated with 11β-HSD2 protein expression (β = 0.56, p < 0.01). A significant alcohol-by-stress interaction was observed with respect to 11β-HSD2 protein expression (p < 0.01). Results indicate that PAE and PS may independently and in combination affect fetal programming of the HPA axis.

Prenatal alcohol exposure alters mRNA expression for stress peptides, glucocorticoid receptor function and immune factors in acutely stressed neonatal brain

Background

The amygdala, hippocampus and hypothalamus are critical stress regulatory areas that undergo functional maturation for stress responding initially established during gestational and early postnatal brain development. Fetal alcohol spectrum disorder (FASD), a consequence of prenatal alcohol exposure (PAE), results in cognitive, mood and behavioral disorders. Prenatal alcohol exposure negatively impacts components of the brain stress response system, including stress-associated brain neuropeptides and glucocorticoid receptors in the amygdala, hippocampus and hypothalamus. While PAE generates a unique brain cytokine expression pattern, little is known about the role of Toll-like receptor 4 (TLR4) and related proinflammatory signaling factors, as well as anti-inflammatory cytokines in PAE brain stress-responsive regions. We hypothesized that PAE sensitizes the early brain stress response system resulting in dysregulated neuroendocrine and neuroimmune activation.

Methods

A single, 4-h exposure of maternal separation stress in male and female postnatal day 10 (PND10) C57Bl/6 offspring was utilized. Offspring were from either prenatal control exposure (saccharin) or a limited access (4 h) drinking-in-the-dark model of PAE. Immediately after stress on PND10, the hippocampus, amygdala and hypothalamus were collected, and mRNA expression was analyzed for stress-associated factors (CRH and AVP), glucocorticoid receptor signaling regulators (GAS5, FKBP51 and FKBP52), astrocyte and microglial activation, and factors associated with TLR4 activation including proinflammatory interleukin-1β (IL-1β), along with additional pro- and anti-inflammatory cytokines. Select protein expression analysis of CRH, FKBP and factors associated with the TLR4 signaling cascade from male and female amygdala was conducted.

Results

The female amygdala revealed increased mRNA expression in stress-associated factors, glucocorticoid receptor signaling regulators and all of the factors critical in the TLR4 activation cascade, while the hypothalamus revealed blunted mRNA expression of all of these factors in PAE following stress. Conversely, far fewer mRNA changes were observed in males, notably in the hippocampus and hypothalamus, but not the amygdala. Statistically significant increases in CRH protein, and a strong trend in increased IL-1β were observed in male offspring with PAE independent of stressor exposure.

Conclusion

Prenatal alcohol exposure creates stress-related factors and TLR-4 neuroimmune pathway sensitization observed predominantly in females, that is unmasked in early postnatal life by a stress challenge.

Binge-like Alcohol Exposure in Adolescence: Behavioural, Neuroendocrine and Molecular Evidence of Abnormal Neuroplasticity… and Return

Binge alcohol consumption among adolescents affects the developing neural networks underpinning reward and stress processing in the nucleus accumbens (NAc). This study explores in rats the long-lasting effects of early intermittent exposure to intoxicating alcohol levels at adolescence, on: (1) the response to natural positive stimuli and inescapable stress; (2) stress-axis functionality; and (3) dopaminergic and glutamatergic neuroadaptation in the NAc. We also assess the potential effects of the non-intoxicating phytocannabinoid cannabidiol, to counteract (or reverse) the development of detrimental consequences of binge-like alcohol exposure. Our results show that adolescent binge-like alcohol exposure alters the sensitivity to positive stimuli, exerts social and novelty-triggered anxiety-like behaviour, and passive stress-coping during early and prolonged withdrawal. In addition, serum corticosterone and hypothalamic and NAc corticotropin-releasing hormone levels progressively increase during withdrawal. Besides, NAc tyrosine hydroxylase levels increase at late withdrawal, while the expression of dopamine transporter, D1 and D2 receptors is dynamically altered during binge and withdrawal. Furthermore, the expression of markers of excitatory postsynaptic signaling—PSD95; Homer-1 and -2 and the activity-regulated spine-morphing proteins Arc, LIM Kinase 1 and FOXP1—increase at late withdrawal. Notably, subchronic cannabidiol, during withdrawal, attenuates social- and novelty-induced aversion and passive stress-coping and rectifies the hyper-responsive stress axis and NAc dopamine and glutamate-related neuroplasticity. Overall, the exposure to binge-like alcohol levels in adolescent rats makes the NAc, during withdrawal, a locus minoris resistentiae as a result of perturbations in neuroplasticity and in stress-axis homeostasis. Cannabidiol holds a promising potential for increasing behavioural, neuroendocrine and molecular resilience against binge-like alcohol harmful effects.

microRNA Expression Profiles in the Ventral Hippocampus during Pubertal Development and the Impact of Peri-Pubertal Binge Alcohol Exposure

Adolescence is hallmarked by two parallel processes of sexual maturation and adult patterning of the brain. Therefore, adolescence represents a vulnerable postnatal period for neurodevelopment where exogenous factors can negatively impact adult brain function. For example, alcohol exposure during pubertal development can lead to long-term and widespread neurobiological dysfunction and these effects have been shown to persist even in the absence of future alcohol exposure. However, the molecular mechanisms mediating the persistent effects of alcohol are unclear. We propose that dysregulation of microRNAs (miR) could be a unifying epigenetic mechanism underlying these widespread long-term changes. We tested the hypothesis that repeated alcohol exposure during pubertal development would cause disruption of normal miR expression profiles during puberty and, subsequently, their downstream mRNA target genes in the ventral hippocampus using an established rat model of adolescent binge drinking. We found 6 alcohol-sensitive miRs that were all downregulated following alcohol exposure and we also investigated the normal age-dependent changes in those miRs throughout the pubertal period. Interestingly, these miRs were normally decreased throughout the process of puberty, but alcohol prematurely exacerbated the normal decline in miR expression levels. The work presented herein provides foundational knowledge about the expression patterns of miRs during this critical period of neurodevelopment. Further, this regulation of miR and mRNA expression by alcohol exposure presents a complex regulatory mechanism by which perturbation in this time-sensitive period could lead to long-term neurological consequences.

Binge Drinking and Intergenerational Implications: Parental Preconception Alcohol Impacts Offspring Development in Rats

Preconception behaviors and experiences of mothers and fathers can affect future offspring. Recently, our laboratory showed that alcohol-naive offspring of parents who were exposed to repeated binge alcohol during adolescence showed altered DNA methylation patterns in the hypothalamus, a brain region involved in regulation of pubertal development, stress, and behavior. These observations have potentially far-reaching consequences for human health, as more than 4.6 million Americans under the age of 21 years report engaging in the rapid intoxication behavior of binge-pattern alcohol (EtOH) drinking. Therefore, we tested the hypothesis that offspring of binge EtOH‒exposed parents would have altered hypothalamic function manifested phenotypically as improper pubertal development, impaired socialization, and dysregulated stress response. In addition, we tested the hypothesis that parental EtOH exposure would confer adaptive protection from the negative effects of EtOH when offspring were themselves exposed to EtOH. Rats received EtOH via oral gavage once daily for 6 days at both early [postnatal day (PND) 37] and late puberty (PND 67). Animals were paired (EtOH-EtOH, vehicle-vehicle) for mating 24 hours after the last EtOH dose. After weaning, offspring were randomized to vehicle treatment to assess changes in normal development or to EtOH treatment to assess the effect of parental EtOH exposure on offspring response to this treatment. We found that offspring had smaller body weights and displayed fewer play behaviors when parents had been exposed to EtOH before conception. In addition, offspring showed a reduction in pubertal development markers that could indicate that parental preconception EtOH exposure confers maladaptive epigenetic traits in first-generation offspring.

Optogenetic silencing of a corticotropin-releasing factor pathway from the central amygdala to the bed nucleus of the stria terminalis disrupts sustained fear

The lateral central nucleus of the amygdala (CeA_L) and the dorsolateral bed nucleus of the stria terminalis (BNST_DL) coordinate the expression of shorter- and longer-lasting fears, respectively. Less is known about how these structures communicate with each other during fear acquisition. One pathway, from the CeA_L to the BNST_DL, is thought to communicate via corticotropin-releasing factor (CRF), but studies have yet to examine its function in fear learning and memory. Thus, we developed an adeno-associated viral-based strategy to selectively target CRF neurons with the optogenetic silencer archaerhodopsin tp009 (CRF-ArchT) to examine the role of CeA_L CRF neurons and projections to the BNST_DL during the acquisition of contextual fear. Expression of our CRF-ArchT vector injected into the amygdala was restricted to CeA_L CRF neurons. Furthermore, CRF axonal projections from the CeA_L clustered around BNST_DL CRF cells. Optogenetic silencing of CeA_L CRF neurons during contextual fear acquisition disrupted retention test freezing 24 h later, but only at later time points (>6 min) during testing. Silencing CeA_L CRF projections in the BNST_DL during contextual fear acquisition produced a similar effect. Baseline contextual freezing, the rate of fear acquisition, freezing in an alternate context after conditioning and responsivity to foot shock were unaffected by optogenetic silencing. Our results highlight how CeA_L CRF neurons and projections to the BNST_DL consolidate longer-lasting components of a fear memory. Our findings have implications for understanding how discrete amygdalar CRF pathways modulate longer-lasting fear in anxiety- and trauma-related disorders.

Histone deacetylase inhibition ameliorates hypertension and hyperglycemia in a model of Cushing's syndrome

Cushing's syndrome (CS) caused by hypercortisolism is occasionally accompanied by metabolic disorders such as hypertension, diabetes mellitus (DM), dyslipidemia, and central obesity. Thus morbidity and mortality, observed in cardiovascular disease, are elevated in patients with CS. We hypothesized that HDAC inhibition (HDACi) decreased transcriptional activity of glucocorticoid receptor (GR), which ameliorates hypertension and hyperglycemia in patients with CS. To establish an animal model of hypercortisolism, Sprague-Dawley rats were infused with adrenocorticotropic hormone (ACTH, 40 ng/day) or dexamethasone (Dex, 10 μg/day) via osmotic minipumps for 4 wk. Expression of GR target genes was determined by quantitative real-time PCR (qRT-PCR). GR enrichment on specific loci, and across the whole genome, was analyzed by chromatin immunoprecipitation (ChIP) and ChIPseq, respectively. HDACi decreased blood pressure and expression of ion regulators in the kidneys of ACTH-infused rats. Additionally, HDACi reduced deposition of polysaccharide, fasting blood glucose level, glucose intolerance, and expression of gluconeogenesis genes in the livers and kidneys of ACTH- and Dex-infused rats. Among class I HDACs, HDAC1 and HDAC3 interacted with GR. HDAC1 knockdown resulted in increased level of acetylation and decreased transcriptional activity of GR. GR recruitment on the promoters of 2,754 genes, which include ion transporters, channels, and gluconeogenic genes, was significantly decreased by MS-275, a class I HDAC inhibitor. These results indicate that HDACi ameliorates hypertension and hyperglycemia in a model of CS by decreasing the transcriptional activity of GR via elevating its level of acetylation.

Role of the innate immune system in the neuropathological consequences induced by adolescent binge drinking

Adolescence is a critical stage of brain maturation in which important plastic and dynamic processes take place in different brain regions, leading to development of the adult brain. Ethanol drinking in adolescence disrupts brain plasticity and causes structural and functional changes in immature brain areas (prefrontal cortex, limbic system) that result in cognitive and behavioral deficits. These changes, along with secretion of sexual and stress-related hormones in adolescence, may impact self-control, decision making, and risk-taking behaviors that contribute to anxiety and initiation of alcohol consumption. New data support the participation of the neuroimmune system in the effects of ethanol on the developing and adult brain. This article reviews the potential pathological bases that underlie the effects of alcohol on the adolescent brain, such as the contribution of genetic background, the perturbation of epigenetic programming, and the influence of the neuroimmune response. Special emphasis is given to the actions of ethanol in the innate immune receptor toll-like receptor 4 (TLR4), since recent studies have demonstrated that by activating the inflammatory TLR4/NFκB signaling response in glial cells, binge drinking of ethanol triggers the release of cytokines/chemokines and free radicals, which exacerbate the immune response that causes neuroinflammation/neural damage as well as short- and long-term neurophysiological, cognitive, and behavioral dysfunction. Finally, potential treatments that target the neuroimmune response to treat the neuropathological and behavioral consequences of adolescent alcohol abuse are discussed.

Adolescent binge alcohol exposure increases risk assessment behaviors in male Wistar rats after exposure to an acute psychological stressor in adulthood

Teenage binge drinking is a common practice that has been shown to increase the risk for developing mood disorders in adulthood. The hypothalamo-pituitary-adrenal (HPA) axis is often dysfunctional in mood disorder patients, and animal models of adolescent binge alcohol exposure similarly show disordered HPA axis function, even after long periods of alcohol abstinence. Here, we sought to investigate the anxiety-like behavioral consequences of binge alcohol exposure in a Wistar rat model. Male rats were administered alcohol in a binge pattern during peri-puberty, and one month later, anxiety-like behaviors were measured using the elevated plus maze. A subset of the rats then underwent 30min of restraint stress, and the anxiety-like behaviors were measured again. We observed an increase in risk assessment behaviors due to both adolescent binge alcohol exposure and restraint stress, but no differences in canonical anxiety-like behaviors. We also repeated the observation that adolescent binge alcohol induces long-term changes in HPA axis sensitivity. Therefore, we concluded that a history of peri-pubertal binge alcohol exposure subtly alters the behavioral response to subsequent acute psychological stress during adulthood, which may over time contribute to the development of mood disorders. This relatively pragmatic animal model represents a more clinically relevant tool in understanding the molecular mechanisms underlying the long-term effects of adolescent binge drinking.

Chronic Unpredictable Mild Stress Induces Loss of GABA Inhibition in Corticotrophin-Releasing Hormone-Expressing Neurons through NKCC1 Upregulation

INTRODUCTION

Prolonged and repeated stresses cause hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis. The corticotrophin-releasing hormone (CRH)-expressing neurons in the hypothalamic paraventricular nucleus (PVN) are an essential component of the HPA axis.

MATERIALS AND METHODS

Chronic unpredictable mild stress (CUMS) was induced in Sprague-Dawley rats. GABA reversal potentials (EGABA) were determined by using gramicidin-perforated recordings in identified PVN-CRH neurons through expressing enhanced green fluorescent protein driven by the CRH promoter. Plasma corticosterone (CORT) levels were measured in rats implanted with a cannula targeting the lateral ventricles and PVN.

RESULTS

Blocking the GABAA receptor in the PVN with gabazine significantly increased plasma CORT levels in unstressed rats but did not change CORT levels in CUMS rats. CUMS caused a depolarizing shift in EGABA in PVN-CRH neurons compared with EGABA in PVN-CRH neurons in unstressed rats. Furthermore, CUMS induced a long-lasting increase in expression levels of the cation chloride cotransporter Na+-K+-Cl--Cl- (NKCC1) in the PVN but a transient decrease in expression levels of K+-Cl--Cl- in the PVN, which returned to the basal level 5 days after CUMS treatment. The NKCC1 inhibitor bumetanide decreased the basal firing activity of PVN-CRH neurons and normalized EGABA and the gabazine-induced excitatory effect on PVN-CRH neurons in CUMS rats. In addition, central administration of bumetanide decreased basal circulating CORT levels in CUMS rats.

CONCLUSIONS

These data suggest that chronic stress impairs GABAergic inhibition, resulting in HPA axis hyperactivity through upregulation of NKCC1.

Role of oxidative stress in disrupting the function of negative glucocorticoid response element in daily amphetamine-treated rats

Amphetamine (AMPH)-induced appetite suppression is associated with changes in hypothalamic reactive oxygen species (ROS), antioxidants, neuropeptides, and plasma glucocorticoid. This study explored whether ROS and glucocorticoid response element (GRE), which is the promoter site of corticotropin-releasing hormone (CRH) gene, participated in neuropeptides-mediated appetite control. Rats were treated daily with AMPH for four days, and changes in food intake, plasma glucocorticoid and expression levels of hypothalamic neuropeptide Y (NPY), proopiomelanocortin (POMC), superoxide dismutase (SOD), CRH, and glucocorticoid receptor (GR) were examined and compared. Results showed that food intake decreased and NPY gene down-regulated, while POMC, SOD, and CRH gene up-regulated during AMPH treatment. GR and GRE-DNA bindings were disrupted on Day 1 and Day 2 when glucocorticoid levels were still high. Pretreatment with GR inhibitor or ROS scavenger modulated mRNA levels in NPY, POMC, SOD and CRH in AMPH-treated rats. We suggest that disruptions of negative GRE (nGRE) on Day 1 and Day 2 are associated with an increase in oxidative stress during the regulation of NPY/POMC-mediated appetite control in AMPH-treated rats. These results advance the understanding of molecular mechanism in regulating AMPH-mediated appetite suppression.

High Resolution Genomic Scans Reveal Genetic Architecture Controlling Alcohol Preference in Bidirectionally Selected Rat Model

Investigations on the influence of nature vs. nurture on Alcoholism (Alcohol Use Disorder) in human have yet to provide a clear view on potential genomic etiologies. To address this issue, we sequenced a replicated animal model system bidirectionally-selected for alcohol preference (AP). This model is uniquely suited to map genetic effects with high reproducibility, and resolution. The origin of the rat lines (an 8-way cross) resulted in small haplotype blocks (HB) with a corresponding high level of resolution. We sequenced DNAs from 40 samples (10 per line of each replicate) to determine allele frequencies and HB. We achieved ~46X coverage per line and replicate. Excessive differentiation in the genomic architecture between lines, across replicates, termed signatures of selection (SS), were classified according to gene and region. We identified SS in 930 genes associated with AP. The majority (50%) of the SS were confined to single gene regions, the greatest numbers of which were in promoters (284) and intronic regions (169) with the least in exon's (4), suggesting that differences in AP were primarily due to alterations in regulatory regions. We confirmed previously identified genes and found many new genes associated with AP. Of those newly identified genes, several demonstrated neuronal function involved in synaptic memory and reward behavior, e.g. ion channels (Kcnf1, Kcnn3, Scn5a), excitatory receptors (Grin2a, Gria3, Grip1), neurotransmitters (Pomc), and synapses (Snap29). This study not only reveals the polygenic architecture of AP, but also emphasizes the importance of regulatory elements, consistent with other complex traits.

Alcohol Used Disorder (AUD) or Alcoholism extracts a great societal cost in terms of human suffering. Understanding the genetic basis is critical to comprehend, treat and prevent this disease, but difficult in humans, as choice is influenced by nature and nurture. To discover its genetic basis, we used an animal model system that controlled for genetic and non-genetic factors through randomization, study replication, long-term divergent selection, and a controlled environment. We conducted whole genome sequencing in breeds that were either compulsive excessive drinkers or completely abstinent. We discovered consistent alterations in several genes and neurological pathways previously unassociated with alcoholism. These results strengthened our understanding of the genetic basis of alcoholism and revealed potential genetic- and neurological-based treatments.

Effects of prolonged alcohol exposure on somatotrophs and corticotrophs in adult rats: Stereological and hormonal study

Exposure to alcohol alters many physiological processes, including endocrine status. The present study examined whether prolonged alcohol (A) exposure could modulate selected stereological and hormonal aspects of pituitary somatotrophs (growth hormone-GH cells) and corticotrophs (adrenocorticotropic hormone-ACTH cells) in adult rats. Changes in pituitary gland volume; the volume density, total number and volume of GH and ACTH cells following alcohol exposure were evaluated using a stereological system (newCAST), while peripheral GH and ACTH levels were determined biochemically. Our results demonstrated the reduction (p<0.05) of the volume density (37%) and volume of GH cells (29%) in the group A. Also, there was a tendency for the total number of GH cells to be smaller in the group A. Serum GH level was significantly decreased (p<0.05; 70%) in the group A when compared to control values. Moreover, prolonged alcohol exposure induced declines (p<0.05) in volume density (24%) and volume of ACTH cells (29%). The total number of ACTH cells and ACTH level were higher (p<0.05; 42%) in the group A than in control rats. Collectively, these results indicate that prolonged alcohol exposure leads not only to changes in GH and ACTH hormone levels, but also to alterations of the morphological aspects of GH and ACTH cells within the pituitary.

Impaired respiratory function and heightened pulmonary inflammation in episodic binge ethanol intoxication and burn injury

Clinical data indicate that cutaneous burn injuries covering greater than 10% of the total body surface area are associated with significant morbidity and mortality, in which pulmonary complications, including acute respiratory distress syndrome (ARDS), contribute to nearly half of all patient deaths. Approximately 50% of burn patients are intoxicated at the time of hospital admission, which increases days on ventilators by 3-fold, and doubles the length of hospitalization, compared to non-intoxicated burn patients. The most common drinking pattern in the United States is binge drinking, where an individual rapidly consumes alcoholic beverages (4 for women, 5 for men) in 2 h. An estimated 38 million Americans binge drink, often several times per month. Experimental data demonstrate that a single binge-ethanol exposure, prior to scald injury, impairs innate and adaptive immune responses, thereby enhancing infection susceptibility and amplifying pulmonary inflammation, neutrophil infiltration, and edema, and is associated with increased mortality. Since these characteristics are similar to those observed in ARDS burn patients, our study objective was to determine whether ethanol intoxication and burn injury and the subsequent pulmonary congestion affect physiological parameters of lung function, using non-invasive and unrestrained plethysmography in a murine model system. Furthermore, to mirror young adult binge-drinking patterns, and to determine the effect of multiple ethanol exposures on pulmonary inflammation, we utilized an episodic binge-ethanol exposure regimen, where mice were exposed to ethanol for a total of 6 days (3 days ethanol, 4 days rest, 3 days ethanol) prior to burn injury. Our analyses demonstrate mice exposed to episodic binge ethanol and burn injury have higher mortality, increased pulmonary congestion and neutrophil infiltration, elevated neutrophil chemoattractants, and respiratory dysfunction, compared to burn or ethanol intoxication alone. Overall, our study identifies plethysmography as a useful tool for characterizing respiratory function in a murine burn model and for future identification of therapeutic compounds capable of restoring pulmonary functionality.

Preclinical evidence implicating corticotropin-releasing factor signaling in ethanol consumption and neuroadaptation

The results of many studies support the influence of the corticotropin-releasing factor (CRF) system on ethanol (EtOH) consumption and EtOH-induced neuroadaptations that are critical in the addiction process. This review summarizes the preclinical data in this area after first providing an overview of the components of the CRF system. This complex system involves hypothalamic and extra-hypothalamic mechanisms that play a role in the central and peripheral consequences of stressors, including EtOH and other drugs of abuse. In addition, several endogenous ligands and targets make up this system and show differences in their involvement in EtOH drinking and in the effects of chronic or repeated EtOH treatment. In general, genetic and pharmacological approaches paint a consistent picture of the importance of CRF signaling via type 1 CRF receptors (CRF(1)) in EtOH-induced neuroadaptations that result in higher levels of intake, encourage alcohol seeking during abstinence and alter EtOH sensitivity. Furthermore, genetic findings in rodents, non-human primates and humans have provided some evidence of associations of genetic polymorphisms in CRF-related genes with EtOH drinking, although additional data are needed. These results suggest that CRF(1) antagonists have potential as pharmacotherapeutics for alcohol use disorders. However, given the broad and important role of these receptors in adaptation to environmental and other challenges, full antagonist effects may be too profound and consideration should be given to treatments with modulatory effects.

Ethanol-related alterations in gene expression patterns in the developing murine hippocampus

It is well known that consuming alcohol prior to and during pregnancy can cause harm to the developing fetus. Fetal alcohol spectrum disorder is a term commonly used to describe a range of disabilities that may arise from prenatal alcohol exposure such as fetal alcohol syndrome, partial fetal alcohol syndrome, alcohol-related neurodevelopmental disorders, and alcohol-related birth defects. Here, we report that maternal binge alcohol consumption alters several important genes that are involved in nervous system development in the mouse hippocampus at embryonic day 18. Microarray analysis revealed that Nova1, Ntng1, Gal, Neurog2, Neurod2, and Fezf2 gene expressions are altered in the fetal hippocampus. Pathway analysis also revealed the association of the calcium signaling pathway in addition to other pathways with the differentially expressed genes during early brain development. Alteration of such important genes and dynamics of the signaling pathways may cause neurodevelopmental disorders. Our findings offer insight into the molecular mechanism involved in neurodevelopmental disorders associated with alcohol-related defects.

Clock genes × stress × reward interactions in alcohol and substance use disorders

Adverse life events and highly stressful environments have deleterious consequences for mental health. Those environmental factors can potentiate alcohol and drug abuse in vulnerable individuals carrying specific genetic risk factors, hence producing the final risk for alcohol- and substance-use disorders development. The nature of these genes remains to be fully determined, but studies indicate their direct or indirect relation to the stress hypothalamo-pituitary-adrenal (HPA) axis and/or reward systems. Over the past decade, clock genes have been revealed to be key-players in influencing acute and chronic alcohol/drug effects. In parallel, the influence of chronic stress and stressful life events in promoting alcohol and substance use and abuse has been demonstrated. Furthermore, the reciprocal interaction of clock genes with various HPA-axis components, as well as the evidence for an implication of clock genes in stress-induced alcohol abuse, have led to the idea that clock genes, and Period genes in particular, may represent key genetic factors to consider when examining gene × environment interaction in the etiology of addiction. The aim of the present review is to summarize findings linking clock genes, stress, and alcohol and substance abuse, and to propose potential underlying neurobiological mechanisms.

Sustained action of developmental ethanol exposure on the cortisol response to stress in zebrafish larvae and adults

Background

Ethanol exposure during pregnancy is one of the leading causes of preventable birth defects, leading to a range of symptoms collectively known as fetal alcohol spectrum disorder. More moderate levels of prenatal ethanol exposure lead to a range of behavioural deficits including aggression, poor social interaction, poor cognitive performance and increased likelihood of addiction in later life. Current theories suggest that adaptation in the hypothalamo-pituitary-adrenal (HPA) axis and neuroendocrine systems contributes to mood alterations underlying behavioural deficits and vulnerability to addiction. In using zebrafish (Danio rerio), the aim is to determine whether developmental ethanol exposure provokes changes in the hypothalamo-pituitary-interrenal (HPI) axis (the teleost equivalent of the HPA), as it does in mammalian models, therefore opening the possibilities of using zebrafish to elucidate the mechanisms involved, and to test novel therapeutics to alleviate deleterious symptoms.

Results and Conclusions

The results showed that developmental exposure to ambient ethanol, 20mM-50mM 1-9 days post fertilisation, had immediate effects on the HPI, markedly reducing the cortisol response to air exposure stress, as measured by whole body cortisol content. This effect was sustained in adults 6 months later. Morphology, growth and locomotor activity of the animals were unaffected, suggesting a specific action of ethanol on the HPI. In this respect the data are consistent with mammalian results, although they contrast with the higher corticosteroid stress response reported in rats after developmental ethanol exposure. The mechanisms that underlie the specific sensitivity of the HPI to ethanol require elucidation.

Investigational therapies for the pharmacological treatment of alcoholism

Introduction: Alcohol dependence is one of the most important psychiatric disorders leading to enormous harm in individuals and indeed within society. Yet, although alcohol dependence is a disease of significant importance, the availability of efficacious pharmacological treatment is still limited. Areas covered: The current review focuses on neurobiological pathways that are the rationale for recent preclinical and clinical studies testing novel compounds that could be used as treatments for alcohol dependence. These neurobiological mechanisms include the: glutamatergic, dopaminergic and GABA mediated pathways as well as neuroendocrine systems. There is also an interest in the approaches for influencing chromatin structure. Expert opinion: There are several compounds in Phase I and Phase II clinical studies that have produced potentially useful results for the treating alcoholism. Further evaluation is still necessary, and the implementation of Phase III studies will help to elucidate the usefulness of these compounds. It is important that personalized approaches (e.g., pharmacogenomics) are investigated in these later studies, as the efficacy of different compounds may vary substantially between subgroups of patients.

Long-term effects of peripubertal binge EtOH exposure on hippocampal microRNA expression in the rat

Adolescent binge alcohol abuse induces long-term changes in gene expression, which impacts the physiological stress response and memory formation, two functions mediated in part by the ventral (VH) and dorsal (DH) hippocampus. microRNAs (miRs) are small RNAs that play an important role in gene regulation and are potential mediators of long-term changes in gene expression. Two genes important for regulating hippocampal functions include brain-derived neurotrophic factor (BDNF) and sirtuin-1 (SIRT1), which we identified as putative gene targets of miR-10a-5p, miR-26a, miR-103, miR-495. The purpose of this study was to quantify miR-10a-5p, miR-26a, miR-103, miR-495 expression levels in the dorsal and ventral hippocampus of male Wistar rats during normal pubertal development and then assess the effects of repeated binge-EtOH exposure. In addition, we measured the effects of binge EtOH-exposure on hippocampal Drosha and Dicer mRNA levels, as well as the putative miR target genes, BDNF and SIRT1. Overall, mid/peri-pubertal binge EtOH exposure altered the normal expression patterns of all miRs tested in an age- and brain region-dependent manner and this effect persisted for up to 30 days post-EtOH exposure. Moreover, our data revealed that mid/peri-pubertal binge EtOH exposure significantly affected miR biosynthetic processing enzymes, Drosha and Dicer. Finally, EtOH-induced significant changes in the expression of a subset of miRs, which correlated with changes in the expression of their predicted target genes. Taken together, these data demonstrate that EtOH exposure during pubertal development has long-term effects on miRNA expression in the rat hippocampus.

All-trans retinoic acid-induced hypothalamus-pituitary-adrenal hyperactivity involves glucocorticoid receptor dysregulation

Clinical reports have highlighted a role for retinoids in the etiology of mood disorders. Although we had shown that recruitment of the nuclear receptor retinoic acid receptor-α (RAR-α) to corticotropin-releasing hormone (CRH) promoter is implicated in activation of the hypothalamus-pituitary-adrenal (HPA) axis, further insight into how retinoids modulate HPA axis activity is lacking. Here we show that all-trans retinoic acid (RA)-induced HPA activation involves impairments in glucocorticoid receptor (GR) negative feedback. RA was applied to rats chronically through intracerebroventricular injection. A 19-day RA exposure induced potent HPA axis activation and typical depression-like behavior. Dexamethasone failed to suppress basal corticosterone (CORT) secretion, which is indicative of a disturbed GR negative feedback. In the hypothalamic paraventricular nucleus, increased CRH⁺ and c-fos⁺ cells were found while a negative R-2⁺/ER⁺ correlation was present between the number of RAR-α⁺ and GR⁺ cells. This was paralleled by increased RAR-α and decreased GR protein expression in the hypothalamus. Additional in vitro studies confirmed that RA abolished GR-mediated glucocorticoid-induced suppression of CRH expression, indicating a negative cross-talk between RAR-α and GR signaling pathways. Finally, the above changes could be rapidly normalized by treatment with GR antagonist mifepristone. We conclude that in addition to the 'classic' RAR-α-mediated transcriptional control of CRH expression, disturbances in GR negative feedback constitute a novel pathway that underlies RA-induced HPA axis hyperactivity. The rapid normalization by mifepristone may be of potential clinical interest in this respect.

Role of prefrontal cortex glucocorticoid receptors in stress and emotion

BACKGROUND

Stress-related disorders (e.g., depression) are associated with hypothalamic-pituitary-adrenocortical axis dysregulation and prefrontal cortex (PFC) dysfunction, suggesting a functional link between aberrant prefrontal corticosteroid signaling and mood regulation.

METHODS

We used a virally mediated knockdown strategy (short hairpin RNA targeting the glucocorticoid receptor [GR]) to attenuate PFC GR signaling in the rat PFC. Adult male rats received bilateral microinjections of vector control or short hairpin RNA targeting the GR into the prelimbic (n = 44) or infralimbic (n = 52) cortices. Half of the animals from each injection group underwent chronic variable stress, and all were subjected to novel restraint. The first 2 days of chronic variable stress were used to assess depression- and anxiety-like behavior in the forced swim test and open field.

RESULTS

The GR knockdown confined to the infralimbic PFC caused acute stress hyper-responsiveness, sensitization of stress responses after chronic variable stress, and induced depression-like behavior (increased immobility in the forced swim test). Knockdown of GR in the neighboring prelimbic PFC increased hypothalamic-pituitary-adrenocortical axis responses to acute stress and caused hyperlocomotion in the open field, but did not affect stress sensitization or helplessness behavior.

CONCLUSIONS

The data indicate a marked functional heterogeneity of glucocorticoid action in the PFC and highlight a prominent role for the infralimbic GR in appropriate stress adaptation, emotional control, and mood regulation.

Regulation of hypothalamic corticotropin-releasing hormone transcription by elevated glucocorticoids

Negative glucocorticoid feedback is essential for preventing the deleterious effects of excessive hypothalamic pituitary adrenal axis axis activation, with an important target being CRH transcription in the hypothalamic paraventricular nucleus. The aim of these studies was to determine whether glucocorticoids repress CRH transcription directly in CRH neurons, by examining glucocorticoid effects on glucocorticoid receptor (GR)-CRH promoter interaction and the activation of proteins required for CRH transcription. Immunoprecipitation of hypothalamic chromatin from intact or adrenalectomized rats subjected to either stress or corticosterone injections showed minor association of the proximal CRH promoter with the GR compared with that with phospho-CREB (pCREB). In contrast, the Period-1 (Per1, a glucocorticoid-responsive gene) promoter markedly recruited GR. Stress increased pCREB recruitment by the CRH but not the Per1 promoter, irrespective of circulating glucocorticoids. In vitro, corticosterone pretreatment (30 minutes or 18 hours) only slightly inhibited basal and forskolin-stimulated CRH heteronuclear RNA in primary hypothalamic neuronal cultures and CRH promoter activity in hypothalamic 4B cells. In 4B cells, 30 minutes or 18 hours of corticosterone exposure had no effect on forskolin-induced nuclear accumulation of the recognized CRH transcriptional regulators, pCREB and transducer of regulated CREB activity 2. The data show that inhibition of CRH transcription by physiological glucocorticoids in vitro is minor and that direct interaction of GR with DNA in the proximal CRH promoter may not be a major mechanism of CRH gene repression. Although GR interaction with distal promoter elements may have a role, the data suggest that transcriptional repression of CRH by glucocorticoids involves protein-protein interactions and/or modulation of afferent inputs to the hypothalamic paraventricular nucleus.

17β-Estradiol is required for the sexually dimorphic effects of repeated binge-pattern alcohol exposure on the HPA axis during adolescence

Alcohol consumption during adolescence has long-term sexually dimorphic effects on anxiety behavior and mood disorders. We have previously shown that repeated binge-pattern alcohol exposure increased the expression of two critical central regulators of stress and anxiety, corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP), in adolescent male rats. By contrast, there was no effect of alcohol on these same genes in adolescent females. Therefore, we tested the hypothesis that 17β-estradiol (E₂), the predominant sex steroid hormone in females, prevents alcohol-induced changes in CRH and AVP gene expression in the paraventricular nucleus (PVN) of the hypothalamus. To test this hypothesis, postnatal day (PND) 26 females were ovariectomized and given E₂ replacement or cholesterol as a control. Next, they were given an alcohol exposure paradigm of 1) saline alone, 2) acute (single dose) or 3) a repeated binge-pattern. Our results showed that acute and repeated binge-pattern alcohol treatment increased plasma ACTH and CORT levels in both E₂- and Ch-treated groups, however habituation to repeated binge-pattern alcohol exposure was evident only in E₂-treated animals. Further, repeated binge-pattern alcohol exposure significantly decreased CRH and AVP mRNA in Ch-, but not E₂-treated animals, which was consistent with our previous observations in gonad intact females. We further tested the effects of E₂ and alcohol treatment on the activity of the wild type CRH promoter in a PVN-derived neuronal cell line. Alcohol increased CRH promoter activity in these cells and concomitant treatment with E₂ completely abolished the effect. Together our data suggest that E₂ regulates the reactivity of the HPA axis to a repeated stressor through modulation of the habituation response and further serves to maintain normal steady state mRNA levels of CRH and AVP in the PVN in response to a repeated alcohol stressor.

BDNF and glucocorticoids regulate corticotrophin-releasing hormone (CRH) homeostasis in the hypothalamus

Regulation of the hypothalamic-pituitary-adrenal (HPA) axis is critical for adaptation to environmental changes. The principle regulator of the HPA axis is corticotrophin-releasing hormone (CRH), which is made in the parventricular nucleus and is an important target of negative feedback by glucocorticoids. However, the molecular mechanisms that regulate CRH are not fully understood. Disruption of normal HPA axis activity is a major risk factor of neuropsychiatric disorders in which decreased expression of the glucocorticoid receptor (GR) has been documented. To investigate the role of the GR in CRH neurons, we have targeted the deletion of the GR, specifically in the parventricular nucleus. Impairment of GR function in the parventricular nucleus resulted in an enhancement of CRH expression and an up-regulation of hypothalamic levels of BDNF and disinhibition of the HPA axis. BDNF is a stress and activity-dependent factor involved in many activities modulated by the HPA axis. Significantly, ectopic expression of BDNF in vivo increased CRH, whereas reduced expression of BDNF, or its receptor TrkB, decreased CRH expression and normal HPA functions. We find the differential regulation of CRH relies upon the cAMP response-element binding protein coactivator CRTC2, which serves as a switch for BDNF and glucocorticoids to direct the expression of CRH.