The cAMP-protein kinase A signal transduction pathway modulates ethanol consumption and sedative effects of ethanol

Brain and eye involvement in McCune-Albright Syndrome: clinical and translational insights

McCune-Albright Syndrome (MAS) is a rare mosaic (post-zygotic) genetic disorder presenting with a broad continuum clinical spectrum. MAS arises from somatic, activating mutations in the GNAS gene, which induces a dysregulated Gsα-protein signaling in several tissues and an increased production of intracellular cyclic adenosine monophosphate (cAMP). Overall, MAS is a rare disorder affecting less than 1/100,000 children and, for this reason, data establishing genotype-phenotype correlations remain limited. Affected individuals clinically present with a variable combination of fibrous dysplasia of bone (FD), extra-skeletal manifestations (including cafeí-au-lait spots) and precocious puberty which might also be associated to broad hyperfunctioning endocrinopathies, and also gastrointestinal and cardiological involvement. Central nervous system (CNS) and eye involvement in MAS are among the less frequently described complications and remain largely uncharacterized. These rare complications mainly include neurodevelopmental abnormalities (e.g., delayed motor development, cognitive and language impairment), CNS anomalies (e.g., Chiari malformation type I) and a wide array of ophthalmological abnormalities often associated with vision loss. The pathophysiological mechanisms underlying abnormal neurological development have not been yet fully elucidated. The proposed mechanisms include a deleterious impact of chronically dysregulated Gsα-protein signaling on neurological function, or a secondary (damaging) effect of (antenatal and/or early postnatal) hypercortisolism on early pre- and post-natal CNS development. In this Review, we summarize the main neurological and ophthalmological features eventually associated with the MAS spectrum, also providing a detailed overview of the potential pathophysiological mechanisms underlying these clinical complications.

Alcohol as a Non-UV Social-Environmental Risk Factor for Melanoma

Although cancer mortality has declined among the general population, the incidence of melanoma continues to rise. While identifying high-risk cohorts with genetic risk factors improves public health initiatives and clinical care management, recognizing modifiable risk factors such as social-environmental risk factors would also affect the methods of patient outreach and education. One major modifiable social-environmental risk factor associated with melanoma is ultraviolet (UV) radiation. However, not all forms of melanoma are correlated with sun exposure or occur in sun-exposed areas. Additionally, UV exposure is rarely associated with tumor progression. Another social-environmental factor, pregnancy, does not explain the sharply increased incidence of melanoma. Recent studies have demonstrated that alcohol consumption is positively linked with an increased risk of cancers, including melanoma. This perspective review paper summarizes epidemiological data correlating melanoma incidence with alcohol consumption, describes the biochemical mechanisms of ethanol metabolism, and discusses how ethanol and ethanol metabolites contribute to human cancer, including melanoma.

Chronic knockdown of the tetraspanin gene CD81 in the mouse nucleus accumbens modulates anxiety and ethanol-related behaviors

CD81, a member of the tetraspanin family, plays important roles in many physiological processes, such as cell motility, attachment, and entry. Yet, CD81 functions in the brain remain unclear. In this study, we investigated the effects of CD81 knockdown, using lentiviral vectors (LV), on anxiety- and ethanol-related behaviors. For this purpose, mice were stereotaxically injected with CD81 shRNA-expressing LV into the nucleus accumbens (Nacc) and were assessed for anxiety-like behavior using the elevated plus maze (EPM) and open field (OF) tests. Alcohol's sedative effects were studied using loss-of-righting-reflex (LORR) and voluntary ethanol intake was assessed using a two-bottle choice (TBC) procedure. Results showed that mice depleted of CD81 exhibited an anxiolytic-like response in the EPM and OF tests with no effect on locomotor activity. In addition, genetic reduction of CD81 in the Nacc increased mice' sensitivity to alcohol's sedative effects in the LORR test, although plasma alcohol concentrations were unaffected. Interestingly, CD81 loss-of-function-induced anxiolysis was accompanied by a significant decrease in ethanol, but not saccharin nor quinine, intake in the TBC procedure. Finally, and following CD81 mRNA quantification, Pearson's correlations showed a significant positive relationship between accumbal CD81 mRNA with anxiety and ethanol-related behaviors. Our data indicate that CD81 is implicated in the pathogenesis of anxiety and alcoholism. Indeed the targeted disruption of CD81, with the resultant decrease in CD81 mRNA in the Nacc, converted ethanol-"preferring" mice into ethanol "non-preferring" mice. Collectively, these findings demonstrate that future CD81-targeted pharmacotherapies may be beneficial for the treatment of anxiety and alcoholism.

Acute Intoxication With Alcohol Reduces Trauma-Induced Proinflammatory Response and Barrier Breakdown in the Lung via the Wnt/β-Catenin Signaling Pathway

Background

Trauma is the third leading cause of mortality worldwide. Upon admission, up to 50% of traumatized patients are acutely intoxicated with alcohol, which might lead to aberrant immune responses. An excessive and uncontrolled inflammatory response to injury is associated with damage to trauma-distant organs. We hypothesize that, along with inflammation-induced apoptosis, the activation of the Wnt/β-catenin signaling pathway would cause breakdown of the lung barrier and the development of lung injury after trauma. It remains unclear whether ethanol intoxication (EI) prior to trauma and hemorrhagic shock will attenuate inflammation and organ injury.

Methods

In this study, 14 male C57BL/6J mice were randomly assigned to two groups and exposed either to EtOH or to NaCl as a control by an oral gavage before receiving a femur fracture (Fx) and hemorrhagic shock, followed by resuscitation (THFx). Fourteen sham animals received either EtOH or NaCl and underwent surgical procedures without THFx induction. After 24 h, oil red O staining of fatty vacuoles in the liver was performed. Histological lung injury score (LIS) was assessed to analyze the trauma-induced RLI. Gene expression of Cxcl1, Il-1β, Muc5ac, Tnf, and Tnfrsf10b as well as CXCL1, IL-1β, and TNF protein levels in the lung tissue and bronchoalveolar lavage fluid were determined by RT-qPCR, ELISA, and immunohistological analyses. Infiltrating polymorphonuclear leukocytes (PMNLs) were examined via immunostaining. Apoptosis was detected by activated caspase-3 expression in the lung tissue. To confirm active Wnt signaling after trauma, gene expression of Wnt3a and its inhibitor sclerostin (Sost) was determined. Protein expression of A20 and RIPK4 as possible modulators of the Wnt signaling pathway was analyzed via immunofluorescence.

Results

Significant fatty changes in the liver confirmed the acute EI. Histopathology and decreased Muc5ac expression revealed an increased lung barrier breakdown and concomitant lung injury after THFx versus sham. EI prior trauma decreased lung injury. THFx increased not only the gene expression of pro-inflammatory markers but also the pulmonary infiltration with PMNL and apoptosis versus sham, while EI prior to THFx reduced those changes significantly. EI increased the THFx-reduced gene expression of Sost and reduced the THFx-induced expression of Wnt3a. While A20, RIPK4, and membranous β-catenin were significantly reduced after trauma, they were enhanced upon EI.

Conclusion

These findings suggest that acute EI alleviates the uncontrolled inflammatory response and lung barrier breakdown after trauma by suppressing the Wnt/β-catenin signaling pathway.

The Placenta as a Target for Alcohol During Pregnancy: The Close Relation with IGFs Signaling Pathway

Alcohol is one of the most consumed drugs in the world, even during pregnancy. Its use is a risk factor for developing adverse outcomes, e.g. fetal death, miscarriage, fetal growth restriction, and premature birth, also resulting in fetal alcohol spectrum disorders. Ethanol metabolism induces an oxidative environment that promotes the oxidation of lipids and proteins, triggers DNA damage, and advocates mitochondrial dysfunction, all of them leading to apoptosis and cellular injury. Several organs are altered due to this harmful behavior, the brain being one of the most affected. Throughout pregnancy, the human placenta is one of the most important organs for women's health and fetal development, as it secretes numerous hormones necessary for a suitable intrauterine environment. However, our understanding of the human placenta is very limited and even more restricted is the knowledge of the impact of toxic substances in its development and fetal growth. So, could ethanol consumption during this period have wounding effects in the placenta, compromising proper fetal organ development? Several studies have demonstrated that alcohol impairs various signaling cascades within G protein-coupled receptors and tyrosine kinase receptors, mainly through its action on insulin and insulin-like growth factor 1 (IGF-1) signaling pathway. This last cascade is involved in cell proliferation, migration, and differentiation and in placentation. This review tries to examine the current knowledge and gaps in our existing understanding of the ethanol effects in insulin/IGFs signaling pathway, which can explain the mechanism to elucidate the adverse actions of ethanol in the maternal-fetal interface of mammals.

Normal Ethanol Sensitivity and Rapid Tolerance Require the G Protein Receptor Kinase 2 in Ellipsoid Body Neurons in Drosophila

BACKGROUND

G protein signaling pathways are key neuromodulatory mechanisms for behaviors and neurological functions that affect the impact of ethanol (EtOH) on locomotion, arousal, and synaptic plasticity. Here, we report a novel role for the Drosophila G protein-coupled receptor kinase 2 (GPRK2) as a member of the GRK4/5/6 subfamily in modulating EtOH-induced behaviors.

METHODS

We studied the requirement of Drosophila Gprk2 for naïve sensitivity to EtOH sedation and ability of the fly to develop rapid tolerance after a single exposure to EtOH, using the loss of righting reflex (LORR) and fly group activity monitor (FlyGrAM) assays.

RESULTS

Loss-of-function Gprk2 mutants demonstrate an increase in alcohol-induced hyperactivity, reduced sensitivity to the sedative effects of EtOH, and diminished rapid tolerance after a single intoxicating exposure. The requirement for Gprk2 in EtOH sedation and rapid tolerance maps to ellipsoid body neurons within the Drosophila brain, suggesting that wild-type Gprk2 is required for modulation of locomotion and alertness. However, even though Gprk2 loss of function leads to decreased and fragmented sleep, this change in the sleep state does not depend on Gprk2 expression in the ellipsoid body.

CONCLUSION

Our work on GPRK2 has established a role for this GRK4/5/6 subfamily member in EtOH sensitivity and rapid tolerance.

Single-Cell Encapsulation via Click-Chemistry Alters Production of Paracrine Factors from Neural Progenitor Cells

Extracellular matrix (ECM) properties affect multiple cellular processes such as cell survival, proliferation, and protein synthesis. Thus, a polymeric-cell delivery system with the ability to manipulate the extracellular environment can act as a fundamental regulator of cell function. Given the promise of stem cell therapeutics, a method to uniformly enhance stem cell function, in particular trophic factor release, can prove transformative in improving efficacy and increasing feasibility by reducing the total number of cells required. Herein, a click-chemistry powered 3D, single-cell encapsulation method aimed at synthesizing a polymeric coating with the optimal thickness around neural progenitor cells is introduced. Polymer encapsulation of neural stem cells significantly increases the release of neurotrophic factors such as VEGF and CNTF. Cell encapsulation with a soft extracellular polymer upregulates the ADCY8-cAMP pathway, suggesting a mechanism for the increase in paracrine factors. Hence, the described single-cell encapsulation technique can emerge as a translatable, nonviral cell modulation method and has the potential to improve stem cells' therapeutic effect.

Epigenetic aging is accelerated in alcohol use disorder and regulated by genetic variation in APOL2

To investigate the potential role of alcohol use disorder (AUD) in aging processes, we employed Levine's epigenetic clock (DNAm PhenoAge) to estimate DNA methylation age in 331 individuals with AUD and 201 healthy controls (HC). We evaluated the effects of heavy, chronic alcohol consumption on epigenetic age acceleration (EAA) using clinical biomarkers, including liver function test enzymes (LFTs) and clinical measures. To characterize potential underlying genetic variation contributing to EAA in AUD, we performed genome-wide association studies (GWAS) on EAA, including pathway analyses. We followed up on relevant top findings with in silico expression quantitative trait loci (eQTL) analyses for biological function using the BRAINEAC database. There was a 2.22-year age acceleration in AUD compared to controls after adjusting for gender and blood cell composition (p = 1.85 × 10^-5). This association remained significant after adjusting for race, body mass index, and smoking status (1.38 years, p = 0.02). Secondary analyses showed more pronounced EAA in individuals with more severe AUD-associated phenotypes, including elevated gamma-glutamyl transferase (GGT) and alanine aminotransferase (ALT), and higher number of heavy drinking days (all ps < 0.05). The genome-wide meta-analysis of EAA in AUD revealed a significant single nucleotide polymorphism (SNP), rs916264 (p = 5.43 × 10^-8), in apolipoprotein L2 (APOL2) at the genome-wide level. The minor allele A of rs916264 was associated with EAA and with increased mRNA expression in hippocampus (p = 0.0015). Our data demonstrate EAA in AUD and suggest that disease severity further accelerates epigenetic aging. EAA was associated with genetic variation in APOL2, suggesting potential novel biological mechanisms for age acceleration in AUD.

Perineurial Barrier Glia Physically Respond to Alcohol in an Akap200-Dependent Manner to Promote Tolerance

Ethanol is the most common drug of abuse. It exerts its behavioral effects by acting on widespread neural circuits; however, its impact on glial cells is less understood. We show that Drosophila perineurial glia are critical for ethanol tolerance, a simple form of behavioral plasticity. The perineurial glia form the continuous outer cellular layer of the blood-brain barrier and are the interface between the brain and the circulation. Ethanol tolerance development requires the A kinase anchoring protein Akap200 specifically in perineurial glia. Akap200 tightly coordinates protein kinase A, actin, and calcium signaling at the membrane to control tolerance. Furthermore, ethanol causes a structural remodeling of the actin cytoskeleton and perineurial membrane topology in an Akap200-dependent manner, without disrupting classical barrier functions. Our findings reveal an active molecular signaling process in the cells at the blood-brain interface that permits a form of behavioral plasticity induced by ethanol.

Gαi and Gβγ subunits have opposing effects on dexmedetomidine-induced sedation

Dexmedetomidine (DMED) is a potent and highly selective α₂-adrenergic receptor agonist and is widely used for short-term sedation. However, the mechanism of DMED-induced sedation has not been deciphered. In the present study, we investigated the mechanism of G_αi and G_βγ subunits on DMED-induced sedation. An ED₅₀ of DMED-induced loss of righting reflex (200.0nmol/kg) was increased to 375.0 or 433.3nmol/kg after pre-treatment with cAMP analog dbcAMP (50nmol/5 μl/mouse, i.c.v.) or the phosphodiesterase 4 inhibitor rolipram (100nmol/5 μl/mouse, i.c.v.). Conversely, the ED₅₀ of DMED-induced LORR decreased to 113.6 or 136.5 nmol/kg after pre-treated with G_βγ subunit inhibitor M119 (100 mg/kg, i.p.) or gallein (100 mg/kg, i.p.) respectively. Administration of dbcAMP, rolipram, gallein or M119 alone had no effect on LORR. Gallein (10 μM) significantly inhibited forskolin-stimulated cAMP accumulation in α_2A-AR -CHO cells. Compared with G_βγ subunit inhibitors or DMED alone, [Ca²⁺]i and pERK1/2 was significantly increased after co-administration with G_βγ subunit inhibitors and DMED. DbcAMP (5 μM) or rolipram (5 μM) alone had no effect on ERK1/2 phosphorylation, but decreased DMED-induced ERK1/2 phosphorylation after co-administration with DMED. G_βγ subunit inhibitor treatment increased DMED-induced phosphorylation of CREB, whereas dbcAMP or rolipram had no effect on pCREB induced by DMED. From our results we conclude that, G_βγ subunit may inhibit DMED-induced sedation through the cAMP and pERK1/2 pathway.

Drosophila: An Emergent Model for Delineating Interactions between the Circadian Clock and Drugs of Abuse

Endogenous circadian oscillators orchestrate rhythms at the cellular, physiological, and behavioral levels across species to coordinate activity, for example, sleep/wake cycles, metabolism, and learning and memory, with predictable environmental cycles. The 21st century has seen a dramatic rise in the incidence of circadian and sleep disorders with globalization, technological advances, and the use of personal electronics. The circadian clock modulates alcohol- and drug-induced behaviors with circadian misalignment contributing to increased substance use and abuse. Invertebrate models, such as Drosophila melanogaster, have proven invaluable for the identification of genetic and molecular mechanisms underlying highly conserved processes including the circadian clock, drug tolerance, and reward systems. In this review, we highlight the contributions of Drosophila as a model system for understanding the bidirectional interactions between the circadian system and the drugs of abuse, alcohol and cocaine, and illustrate the highly conserved nature of these interactions between Drosophila and mammalian systems. Research in Drosophila provides mechanistic insights into the corresponding behaviors in higher organisms and can be used as a guide for targeted inquiries in mammals.

Broad-spectrum protein kinase inhibition by the staurosporine analog KT-5720 reverses ethanol withdrawal-associated loss of NeuN/Fox-3

Chronic, intermittent ethanol (CIE) exposure is known to produce neuroadaptive alterations in excitatory neurotransmission that contribute to the development of dependence. Although activation of protein kinases (e.g., cyclic AMP [cAMP]-dependent protein kinase) is implicated in the synaptic trafficking of these receptors following CIE exposure, the functional consequences of these effects are yet to be fully understood. The present study sought to delineate the influence of protein kinase in regulating cytotoxicity following CIE exposure, as well as to examine the relative roles of ethanol exposure and ethanol withdrawal (EWD) in promoting these effects. Rat hippocampal explants were exposed to a developmental model of CIE with or without co-application of broad-spectrum protein kinase inhibitor KT-5720 (1 μM) either during ethanol exposure or EWD. Hippocampal cytotoxicity was assessed via immunofluorescence (IF) of neuron-specific nuclear protein (NeuN) with thionine staining of Nissl bodies to confirm IF findings. Concomitant application of ethanol and KT-5720 restored the loss of NeuN/Fox-3 IF in pyramidal CA1 and granule DG cell layers produced by CIE, but there was no restoration in CA3. Application of KT-5720 during EWD failed to significantly alter levels of NeuN IF, implying that ethanol exposure activates protein kinases that, in part, mediate the effects of EWD. KT-5720 application during EWD also restored thionine staining in CA1, suggesting kinase regulation of both neurons and non-neuronal cells. These data demonstrate that CIE exposure alters protein kinase activity to promote ethanol withdrawal-associated loss of NeuN/Fox-3 and highlight the influence of kinase signaling on distinct cell types in the developing hippocampus.

Molecular mechanisms underlying alcohol-drinking behaviours

The main characteristic of alcohol use disorder is the consumption of large quantities of alcohol despite the negative consequences. The transition from the moderate use of alcohol to excessive, uncontrolled alcohol consumption results from neuroadaptations that cause aberrant motivational learning and memory processes. Here, we examine studies that have combined molecular and behavioural approaches in rodents to elucidate the molecular mechanisms that keep the social intake of alcohol in check, which we term 'stop pathways', and the neuroadaptations that underlie the transition from moderate to uncontrolled, excessive alcohol intake, which we term 'go pathways'. We also discuss post-transcriptional, genetic and epigenetic alterations that underlie both types of pathways.

Ethanol modulates facial stimulation-evoked outward currents in cerebellar Purkinje cells in vivo in mice

Acute ethanol overdose can induce dysfunction of cerebellar motor regulation and cerebellar ataxia. In this study, we investigated the effect of ethanol on facial stimulation-evoked inhibitory synaptic responses in cerebellar Purkinje cells (PCs) in urethane-anesthetized mice, using in vivo patch-clamp recordings. Under voltage-clamp conditions, ethanol (300 mM) decreased the amplitude, half-width, rise time and decay time of facial stimulation-evoked outward currents in PCs. The ethanol-induced inhibition of facial stimulation-evoked outward currents was dose-dependent, with an IC₅₀ of 148.5 mM. Notably, the ethanol-induced inhibition of facial stimulation-evoked outward currents were significantly abrogated by cannabinoid receptor 1 (CB1) antagonists, AM251 and O-2050, as well as by the CB1 agonist WIN55212-2. Moreover, the ethanol-induced inhibition of facial stimulation-evoked outward currents was prevented by cerebellar surface perfusion of the PKA inhibitors H-89 and Rp-cAMP, but not by intracellular administration of the PKA inhibitor PKI. Our present results indicate that ethanol inhibits the facial stimulation-evoked outward currents by activating presynaptic CB1 receptors via the PKA signaling pathway. These findings suggest that ethanol overdose impairs sensory information processing, at least in part, by inhibiting GABA release from molecular layer interneurons onto PCs.

Inflexible ethanol intake: A putative link with the Lrrk2 pathway

Alcoholism is a complex multifactorial disorder with a strong genetic influence. Although several studies have shown the impact of high ethanol intake on the striatal gene expression, few have addressed the relationship between the patterns of gene expression underlying the compulsive behaviour associated with the two major concerns in addiction: the excessive drug consumption and relapsing. In this study, we used a chronic three-bottle free-choice murine model to address striatal transcript regulation among animals with different ethanol intakes and preferences: Light Drinkers (preference for water throughout the experiment), Heavy Drinkers (preference for ethanol with a non-compulsive intake) and Inflexible Drinkers (preference for ethanol and simultaneous loss of control over the drug intake). Our aim was to correlate the intake patterns observed in this model with gene expression changes in the striatum, a brain region critical for the development of alcohol addiction. We found that the transcripts of the Lrrk2 gene, which encodes a multifunctional protein with kinase and GTPase activities, is upregulated only in Inflexible Drinkers suggesting, for the first time, that the Lrrk2 pathway plays a major role in the compulsive ethanol intake behaviour of addicted subjects.

Behavioral Neuroadaptation to Alcohol: From Glucocorticoids to Histone Acetylation

A prime mechanism that contributes to the development and maintenance of alcoholism is the dysregulation of the hypothalamic-pituitary-adrenal axis activity and the release of glucocorticoids (cortisol in humans and primates, corticosterone in rodents) from the adrenal glands. In the brain, sustained, local elevation of glucocorticoid concentration even long after cessation of chronic alcohol consumption compromises functional integrity of a circuit, including the prefrontal cortex (PFC), the hippocampus (HPC), and the amygdala (AMG). These structures are implicated in learning and memory processes as well as in orchestrating neuroadaptive responses to stress and anxiety responses. Thus, potentiation of anxiety-related neuroadaptation by alcohol is characterized by an abnormally AMG hyperactivity coupled with a hypofunction of the PFC and the HPC. This review describes research on molecular and epigenetic mechanisms by which alcohol causes distinct region-specific adaptive changes in gene expression patterns and ultimately leads to a variety of cognitive and behavioral impairments on prefrontal- and hippocampal-based tasks. Alcohol-induced neuroadaptations involve the dysregulation of numerous signaling cascades, leading to long-term changes in transcriptional profiles of genes, through the actions of transcription factors such as [cAMP response element-binding protein (CREB)] and chromatin remodeling due to posttranslational modifications of histone proteins. We describe the role of prefrontal-HPC-AMG circuit in mediating the effects of acute and chronic alcohol on learning and memory, and region-specific molecular and epigenetic mechanisms involved in this process. This review first discusses the importance of brain region-specific dysregulation of glucocorticoid concentration in the development of alcohol dependence and describes how persistently increased glucocorticoid levels in PFC may be involved in mediating working memory impairments and neuroadaptive changes during withdrawal from chronic alcohol intake. It then highlights the role of cAMP-PKA-CREB signaling cascade and histone acetylation within the PFC and limbic structures in alcohol-induced anxiety and behavioral impairments, and how an understanding of functional alterations of these pathways might lead to better treatments for neuropsychiatric disorders.

Phosphodiesterase regulation of alcohol drinking in rodents

Alcohol use disorders are chronically relapsing conditions characterized by persistent drinking despite the negative impact on one's life. The difficulty of achieving and maintaining sobriety suggests that current treatments fail to fully address the underlying causes of alcohol use disorders. Identifying additional pathways controlling alcohol consumption may uncover novel targets for medication development to improve treatment options. One family of proteins recently implicated in the regulation of alcohol consumption is the cyclic nucleotide phosphodiesterases (PDEs). As an integral component in the regulation of the second messengers cyclic AMP and cyclic GMP, and thus their cognate signaling pathways, PDEs present intriguing targets for pharmacotherapies to combat alcohol use disorders. As activation of cAMP/cGMP-dependent signaling cascades can dampen alcohol intake, PDE inhibitors may provide a novel target for reducing excessive alcohol consumption, as has been proposed for PDE4 and PDE10A. This review highlights preclinical literature demonstrating the involvement of cyclic nucleotide-dependent signaling in neuronal and behavioral responses to alcohol, as well as detailing the capacity of various PDE inhibitors to modulate alcohol intake. Together these data provide a framework for evaluating the potential utility of PDE inhibitors as novel treatments for alcohol use disorders.

Polymorphisms in early neurodevelopmental genes affect natural variation in alcohol sensitivity in adult drosophila

BACKGROUND

Alcohol abuse and alcoholism are significant public health problems, but the genetic basis for individual variation in alcohol sensitivity remains poorly understood. Drosophila melanogaster presents a powerful model system for dissecting the genetic underpinnings that determine individual variation in alcohol-related phenotypes. We performed genome wide association analyses for alcohol sensitivity using the sequenced, inbred lines of the D. melanogaster Genetic Reference Panel (DGRP) together with extreme QTL mapping in an advanced intercross population derived from sensitive and resistant DGRP lines.

RESULTS

The DGRP harbors substantial genetic variation for alcohol sensitivity and tolerance. We identified 247 candidate genes affecting alcohol sensitivity in the DGRP or the DGRP-derived advanced intercross population, some of which met a Bonferroni-corrected significance threshold, while others occurred among the top candidate genes associated with variation in alcohol sensitivity in multiple analyses. Among these were candidate genes associated with development and function of the nervous system, including several genes in the Dopamine decarboxylase (Ddc) cluster involved in catecholamine synthesis. We found that 58 of these genes formed a genetic interaction network. We verified candidate genes using mutational analysis, targeted gene disruption through RNAi knock-down and transcriptional profiling. Two-thirds of the candidate genes have been implicated in previous Drosophila, mouse and human studies of alcohol-related phenotypes.

CONCLUSIONS

Individual variation in alcohol sensitivity in Drosophila is highly polygenic and in part determined by variation in evolutionarily conserved signaling pathways that are associated with catecholamine neurotransmitter biosynthesis and early development of the nervous system.

Role of phosphodiesterase-4 on ethanol elicited locomotion and narcosis

The cAMP signaling pathway has emerged as an important modulator of the pharmacological effects of ethanol. In this respect, the cAMP-dependent protein kinase has been shown to play an important role in the modulation of several ethanol-induced behavioral actions. Cellular levels of cAMP are maintained by the activity of adenylyl cyclases and phosphodiesterases. In the present work we have focused on ascertaining the role of PDE4 in mediating the neurobehavioral effects of ethanol. For this purpose, we have used the selective PDE4 inhibitor Ro 20-1724. This compound has been proven to enhance cellular cAMP response by PDE4 blockade and can be administered systemically. Swiss mice were injected intraperitoneally (i.p.) with Ro 20-1724 (0-5 mg/kg; i.p.) at different time intervals before ethanol (0-4 g/kg; i.p.) administration. Immediately after the ethanol injection, locomotor activity, loss of righting reflex, PKA footprint and enzymatic activity were assessed. Pretreatment with Ro 20-1724 increased ethanol-induced locomotor stimulation in a dose-dependent manner. Doses that increased locomotor stimulation did not modify basal locomotion or the suppression of motor activity produced by high doses of this alcohol. Ro 20-1724 did not alter the locomotor activation produced by amphetamine or cocaine. The time of loss of righting reflex evoked by ethanol was increased after pretreatment with Ro 20-1724. This effect was selective for the narcotic effects of ethanol since Ro 20-1724 did not affect pentobarbital-induced narcotic effects. Moreover, Ro 20-1724 administration increased the PKA footprint and enzymatic activity response elicited by ethanol. These data provide further evidence of the key role of the cAMP signaling pathway in the central effects of ethanol.

CREB-BDNF pathway influences alcohol cue-elicited activation in drinkers

Alcohol use disorder (AUD) is suggested to have polygenic risk factors and also exhibits neurological complications, strongly encouraging a translational study to explore the associations between aggregates of genetic variants and brain function alterations related to alcohol use. In this study, we used a semiblind multivariate approach, parallel independent component analysis with multiple references (pICA-MR) to investigate relationships of genome-wide single nucleotide polymorphisms with alcohol cue-elicited brain activations in 315 heavy drinkers, where pICA-MR assesses multiple reference genes for their architecture and functional influences on neurobiological conditions. The genetic component derived from the cAMP-response element-binding protein and -brain derived neurotrophic factor (CREB-BDNF) pathway reference was significantly associated (r = -0.38, P = 3.98 × 10(-12) ) with an imaging component reflecting hyperactivation in precuneus, superior parietal lobule, and posterior cingulate for drinkers with more severe alcohol dependence symptoms. The highlighted brain regions participate in many cognitive processes and have been robustly implicated in craving-related studies. The genetic factor highlighted the CREB and BDNF references, as well as other genes including GRM5, GRM7, GRID1, GRIN2A, PRKCA, and PRKCB. Ingenuity Pathway Analysis indicated that the genetic component was enriched in synaptic plasticity, GABA, and protein kinase A signaling. Collectively, our findings suggest that genetic variations in various neural plasticity and signaling pathways partially explain the variance of precuneus reactivity to alcohol cues which appears to be associated with AUD severity.

Alcohol-induced sedation and synergistic interactions between alcohol and morphine: a key mechanistic role for Toll-like receptors and MyD88-dependent signaling

Increasing evidence demonstrates induction of proinflammatory Toll-like receptor (TLR) 2 and TLR4 signaling by morphine and, TLR4 signaling by alcohol; thus indicating a common site of drug action and a potential novel innate immune-dependent hypothesis for opioid and alcohol drug interactions. Hence, the current study aimed to assess the role of TLR2, TLR4, MyD88 (as a critical TLR-signaling participant), NF-κB, Interleukin-1β (IL-1β; as a downstream proinflammatory effector molecule) and the μ opioid receptor (MOR; as a classical site for morphine action) in acute alcohol-induced sedation (4.5g/kg) and alcohol (2.5g/kg) interaction with morphine (5mg/kg) by assessing the loss of righting reflex (LORR) as a measure of sedation. Wild-type male Balb/c mice and matched genetically-deficient TLR2, TLR4, and MyD88 strains were utilized, together with pharmacological manipulation of MOR, NF-κB, TLR4 and Interleukin-1β. Alcohol induced significant LORR in wild-type mice; this was halved by MyD88 and TLR4 deficiency, and surprisingly nearly completely eliminated by TLR2 deficiency. In contrast, the interaction between morphine and alcohol was found to be MOR-, NF-κB-, TLR2- and MyD88-dependent, but did not involve TLR4 or Interleukin-1β. Morphine-alcohol interactions caused acute elevations in microglial cell counts and NF-κB-p65 positive cells in the motor cortex in concordance with wild-type and TLR2 deficient mouse behavioral data, implicating neuroimmunopharmacological signaling as a pivotal mechanism in this clinically problematic drug-drug interaction.

Role of CA2+/calmodulin on ethanol neurobehavioral effects

RATIONALE

The cAMP-dependent protein kinase A (PKA) signaling transduction pathway has been shown to play an important role in the modulation of several ethanol-induced behaviors. Different studies have demonstrated intracellular calcium (Ca(2+))-dependent activation of the PKA cascade after ethanol administration. Thus, the cAMP cascade mediator Ca(2+)-dependent calmodulin (CaM) has been strongly implicated in the central effects of ethanol.

OBJECTIVES

In this study, we assessed the role of the CaM inhibitor W7 on ethanol-induced stimulation, ethanol intake, and ethanol-induced activation of PKA.

METHODS

Swiss mice were pretreated with W7 (0-10 mg/kg) 30 min before ethanol (0-3.75 g/kg) administration. Immediately, animals were placed during 20 min in an open-field chamber. Ethanol (10 %, v/v) intake in 2 h was assessed using a limited access paradigm. Experiments with caffeine (0-15 mg/kg), cocaine (0-4 mg/kg), and saccharine (0.1 %, w/v) were designed to compare their results to those obtained with ethanol. Western blot was assayed 45 min after ethanol administration.

RESULTS

Results showed that pretreatment with W7, reduced selectively in a dose-dependent fashion ethanol-induced locomotor stimulation and ethanol intake. The ethanol-induced activation of PKA was also prevented by W7 administration.

CONCLUSIONS

These results demonstrate that CaM inhibition resulted in a selective reduction of ethanol-stimulating effects and ethanol intake. The PKA activation induced by ethanol was blocked after the CaM blockade with W7. These results provide further evidence of the key role of cellular Ca(2+)-dependent pathways on the central effects of ethanol.

Centrally formed acetaldehyde mediates ethanol-induced brain PKA activation

Centrally formed acetaldehyde has proven to be responsible for several psychopharmacological effects induced by ethanol. In addition, it has been suggested that the cAMP-PKA signaling transduction pathway plays an important role in the modulation of several ethanol-induced behaviors. Therefore, we hypothesized that acetaldehyde might be ultimately responsible for the activation of this intracellular pathway. We used three pharmacological agents that modify acetaldehyde activity (α-lipoic acid, aminotriazole, and d-penicillamine) to study the role of this metabolite on EtOH-induced PKA activation in mice. Our results show that the injection of α-lipoic acid, aminotriazole and d-penicillamine prior to acute EtOH administration effectively blocks the PKA-enhanced response to EtOH in the brain. These results strongly support the hypothesis of a selective release of acetaldehyde-dependent Ca(2+) as the mechanism involved in the neurobehavioral effects elicited by EtOH.

Adolescent and adult rat cortical protein kinase A display divergent responses to acute ethanol exposure

Adolescent rats display reduced sensitivity to many dysphoria-related effects of alcohol (ethanol) including motor ataxia and sedative hypnosis, but the underlying neurobiological factors that contribute to these differences remain unknown. The cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) pathway, particularly the type II regulatory subunit (RII), has been implicated in ethanol-induced molecular and behavioral responses in adults. Therefore, the current study examined cerebral cortical PKA in adolescent and adult ethanol responses. With the exception of early adolescence, PKA RIIα and RIIβ subunit levels largely did not differ from adult levels in either whole cell lysate or P2 synaptosomal expression. However, following acute ethanol exposure, PKA RIIβ P2 synaptosomal expression and activity were increased in adults, but not in adolescents. Behaviorally, intracerebroventricular administration of the PKA activator Sp-cAMP and inhibitor Rp-cAMP prior to ethanol administration increased adolescent sensitivity to the sedative-hypnotic effects of ethanol compared to controls. Sp-cAMP was ineffective in adults whereas Rp-cAMP suggestively reduced loss of righting reflex (LORR) with paralleled increases in blood ethanol concentrations. Overall, these data suggest that PKA activity modulates the sedative/hypnotic effects of ethanol and may potentially play a wider role in the differential ethanol responses observed between adolescents and adults.

Molecular and genetic determinants of alcohol dependence

Alcohol dependence is a complex disorder affecting all social and ethnic groups. Although the scientific understanding of the mechanism governing this multifactorial disease is still in its infancy, understanding its biological bases, including the potential contribution of genetic factors, is key to characterizing individual's risk and developing efficacious therapeutic target to combat the disease. This review provides an overview of different approaches that are being increasingly integrated to extend our knowledge of the genetic underpinnings of alcohol dependence.

Animal Models of Psychosis: Current State and Future Directions

Psychosis is an abnormal mental state characterized by disorganization, delusions and hallucinations. Animal models have become an increasingly important research tool in the effort to understand both the underlying pathophysiology and treatment of psychosis. There are multiple animal models for psychosis, with each formed by the coupling of a manipulation and a measurement. In this manuscript we do not address the diseases of which psychosis is a prominent comorbidity. Instead, we summarize the current state of affairs and future directions for animal models of psychosis. To accomplish this, our manuscript will first discuss relevant behavioral and electrophysiological measurements. We then provide an overview of the different manipulations that are combined with these measurements to produce animal models. The strengths and limitations of each model will be addressed in order to evaluate its cross-species comparability.

Deciphering the relationship between vulnerability to ethanol-induced behavioral sensitization and ethanol consumption in outbred mice

Ethanol (EtOH)-induced behavioral sensitization (EIBS) is proposed to play a role in early and recurring steps of alcohol dependence, but its impact on alcohol abuse is not clear. EIBS development is dependent upon animal species, strain and also individual factors. We proposed here to decipher the co-expression of EIBS and EtOH intake in individual animals among outbred Swiss mice, which exhibit heterogeneity that parallels what may occur in humans. To do so, mice were exposed to a two-bottle choice with free access to water or 10% EtOH for 6 days just before and immediately after chronic intraperitoneal 2.5 g/kg ethanol injections once a day for 10 consecutive days. Based on their sensitization scores, mice were split into resistant and sensitized animals. First, we showed that individual susceptibility to EIBS is inversely correlated with voluntary EtOH consumption. Exposure to repeated EtOH during EIBS development increased subsequent EtOH intake among the entire population. Very interestingly, subsequent analyses suggested that the less the mice are sensitized the more they increase their EtOH intake; however, resistant mice were sensitive to EtOH adulteration with quinine, whereas sensitized ones maintained their EtOH intake levels, therefore exhibiting a compulsive-like drinking pattern. In addition, we showed that resistant mice do not exhibit a weaker sensitivity to the aversive properties of EtOH that may contribute to their higher level of EtOH intake compared to sensitized mice. This study confirms and extends previous data showing a deep relationship between propensity for EtOH consumption and susceptibility to EIBS in Swiss mice.

Initial responses to the first dose of nicotine in novel smokers: the role of exposure to environmental smoking and genetic predisposition

BACKGROUND

Sensitivity to initial smoking constitutes an early predictor of the risk of dependence. We investigated the role of exposure to smoking (by parents, siblings, and peers) and reward-related candidate gene polymorphisms (OPRM1 A118G, DRD2 TaqlA and DRD4 bp VNTR) in adolescents' responses to initial smoking.

METHODS

We used cross-sectional survey data and saliva samples from 171 Dutch students who had never inhaled on a cigarette (mean age: 13.9 years). The outcome measure was adolescents' self-reported responses to initial smoking.

RESULTS

Exposure to peer smoking was associated with increased liking (OR = 1.74, CI = 1.13-2.70) and more pleasant sensations (β = .21, p = .01). Exposure to maternal smoking was associated with less unpleasant sensations (β = -.20, p = .01). Adolescents carrying the G-variant of the OPRM1 A118G polymorphism were more likely to report liking (OR = 2.50, CI = 1.09-5.73) and adolescents homozygous for the C-variant of the DRD2 TaqlA polymorphism reported less unpleasant sensations (β = .18, p = .04).

CONCLUSION

Although preliminary, these findings suggest that exposure to environmental smoking and polymorphisms in the OPRM1 and DRD2 gene may affect initial sensitivity to nicotine, an early phenotype of the risk of dependence. In the future, collaborative efforts to combine data from multiple studies in meta-analyses are needed to improve accuracy of estimated effects in genetic studies.

Genetics and genomics of alcohol sensitivity

Alcohol abuse and alcoholism incur a heavy socioeconomic cost in many countries. Both genetic and environmental factors contribute to variation in the inebriating effects of alcohol and alcohol addiction among individuals within and across populations. From a genetics perspective, alcohol sensitivity is a quantitative trait determined by the cumulative effects of multiple segregating genes and their interactions with the environment. This review summarizes insights from model organisms as well as human populations that represent our current understanding of the genetic and genomic underpinnings that govern alcohol metabolism and the sedative and addictive effects of alcohol on the nervous system.

In vivo study of ethanol-activated brain protein kinase A: manipulations of Ca2+ distribution and flux

BACKGROUND

The cAMP-dependent protein kinase (PKA) signaling transduction pathway has been shown to play an important role in the modulation of several ethanol (EtOH)-induced behavioral actions. In vivo, short-term exposure to EtOH up-regulates the cAMP-signaling cascade. Interestingly, different Ca(2+) -dependent cAMP-PKA cascade mediators play a critical role in the neurobehavioral response to EtOH, being of special relevance to the Ca(2+) -dependent adenylyl cyclases 1 and 8. We hypothesize an intracellular PKA activation elicited by EtOH administration, which may be regulated by a Ca(2+) -dependent mechanism as an early cellular response. Thus, the present work aims to explore the role of Ca(2+) (internal and external) on the EtOH-activated PKA cascade.

METHODS

Swiss male mice received an intraperitoneal injection of EtOH (0 or 4 g/kg), and brains were dissected following a temporal pattern (7, 15, 30, 45, 90, or 120 minutes). Either the enzymatic PKA activity or its fingerprint was analyzed on different brain areas (cortex, hypothalamus, hippocampus, and striatum). To explore the role of Ca(2+) on the EtOH-activated PKA cascade, mice were pretreated with diltiazem (0 or 20 mg/kg), dantrolene (0 or 5 mg/kg), or 3,7-Dimethyl-1-(2-propynyl)xanthine (0 or 1 mg/kg) 30 minutes before EtOH (4 g/kg) administration. After 45 minutes of EtOH administration, brains were removed and dissected to measure the PKA activity or its fingerprint.

RESULTS

Results from these experiments showed an EtOH-dependent activation of PKA in different brain areas. Manipulations involving a disruption of intracellular Ca(2+) release from the endoplasmic reticulum resulted in a decreased EtOH-induced activation of PKA. On the contrary, extracellular-to-cytoplasm Ca(2+) manipulations did not prevent the PKA activation by EtOH.

CONCLUSIONS

Altogether, these results show the critical role of stored Ca(2+) as an intracellular mediator of different neurobiological actions of EtOH and provide further evidence of a possible new target for EtOH within the central nervous system.

Ethanol activation of protein kinase A regulates GABAA α1 receptor function and trafficking in cultured cerebral cortical neurons

Ethanol exposure produces alterations in GABAergic signaling that are associated with dependence and withdrawal. Previously, we demonstrated that ethanol-induced protein kinase C (PKC) γ signaling selectively contributes to changes in GABAA α1 synaptic receptor activity and surface expression. Here, we demonstrate that protein kinase A (PKA) exerts opposing effects on GABAA receptor adaptations during brief ethanol exposure. Cerebral cortical neurons from day 0-1 rat pups were tested after 18 days in culture. Receptor trafficking was assessed by Western blot analysis, and functional changes were measured using whole-cell patch-clamp recordings of evoked and miniature inhibitory postsynaptic current (mIPSC) responses. One-hour ethanol exposure increased membrane-associated PKC and PKA, but steady-state GABAA α1 subunit levels were maintained. Activation of PKA by Sp-adenosine 3',5'-cyclic monophosphothioate triethylamine alone increased GABAA α1 subunit surface expression and zolpidem potentiation of GABA responses, whereas coexposure of ethanol with the PKA inhibitor Rp-adenosine 3',5'-cyclic monophosphothioate triethylamine decreased α1 subunit expression and zolpidem responses. Exposure to the PKC inhibitor calphostin-C with ethanol mimicked the effect of direct PKA activation. The effects of PKA modulation on mIPSC decay τ were consistent with its effects on GABA currents evoked in the presence of zolpidem. Overall, the results suggest that PKA acts in opposition to PKC on α1-containing GABAA receptors, mediating the GABAergic effects of ethanol exposure, and may provide an important target for the treatment of alcohol dependence/withdrawal.

Best friends and alcohol use in adolescence: the role of the dopamine D4 receptor gene

The influence of friends and peers is theoretically one of the most consistent and important factors explaining adolescent alcohol use. However, not all adolescents are equally likely to be influenced by their friends' drinking behaviors. Genetic factors may underlie these inter-individual differences in susceptibility to the drinking behavior of friends. Because the long allele (≥ 7 repeats) of the dopamine D4 receptor (DRD4) gene has been associated with susceptibility to alcohol and alcohol-related cues, we tested whether associations between best friend's and adolescent's alcohol use differed for DRD4 genotypes. A Dutch nationwide sample of 308 adolescents (age 13 at baseline) participated in a prospective, community-based study with five annual waves. A cross-lagged path analysis was carried out in Mplus to examine bi-directional relations between friends' and adolescents' weekly alcohol use (number of drinks). A multi-group approach was applied to test for moderation effects of a 48-base pair variable number of tandem repeats polymorphism in exon 3 of the DRD4 gene. Additionally, with latent growth curve models, it was examined whether the interaction between friends' drinking and DRD4 genotype predicted the development of adolescents' alcohol use. Results showed that both cross-sectionally and longitudinally higher levels of friends' alcohol use resulted in higher levels of adolescents' alcohol consumption over time (and vice versa). No significant moderation of DRD4 genotype was found: Associations between adolescents' and friends' drinking did not differ for adolescent carriers of the DRD4 long allele, when compared with adolescents without the DRD4 long allele. Because this is the first study to examine DRD4 × friends' drinking effects prospectively, replication is essential. Future longitudinal studies, possibly with observational or diary designs, are needed to increase our understanding of the interplay between genetic and environmental risk factors for adolescent alcohol use.

Inhibiting the TLR4-MyD88 signalling cascade by genetic or pharmacological strategies reduces acute alcohol-induced sedation and motor impairment in mice

BACKGROUND AND PURPOSE

Emerging evidence implicates a role for toll-like receptor 4 (TLR4) in the CNS effects of alcohol. The aim of the current study was to determine whether TLR4-MyD88-dependent signalling is involved in the acute behavioural actions of alcohol and if alcohol can activate TLR4-downstream MAPK and NF-κB pathways.

EXPERIMENTAL APPROACH

The TLR4 pathway was evaluated using the TLR4 antagonist (+)-naloxone (µ-opioid receptor-inactive isomer) and mice with null mutations in the TLR4 and MyD88 genes. Sedation and motor impairment induced by a single dose of alcohol were assessed by loss of righting reflex (LORR) and rotarod tests, separately. The phosphorylation of JNK, ERK and p38, and levels of IκBα were measured to determine the effects of acute alcohol exposure on MAPK and NF-κB signalling.

KEY RESULTS

After a single dose of alcohol, both pharmacological inhibition of TLR4 signalling with (+)-naloxone and genetic deficiency of TLR4 or MyD88 significantly (P < 0.0001) reduced the duration of LORR by 45-78% and significantly decreased motor impairment recovery time to 62-88% of controls. These behavioural actions were not due to changes in the peripheral or central alcohol pharmacokinetics. IκBα levels responded to alcohol by 30 min in mixed hippocampal cell samples, from wild-type mice, but not in cells from TLR4- or MyD88-deficient mice.

CONCLUSIONS AND IMPLICATIONS

These data provide new evidence that TLR4-MyD88 signalling is involved in the acute behavioural actions of alcohol in mice.

Investigation of calcium-stimulated adenylyl cyclases 1 and 8 on toluene and ethanol neurobehavioral actions

The abused inhalant toluene has potent behavioral effects, but only recently has progress been made in understanding the molecular pathways that mediate the action of toluene in the brain. Toluene and ethanol induce similar behavioral effects and share some targets including NMDA and GABA receptors. In studies examining neuronal actions of ethanol, mice lacking the calcium-stimulated adenylyl cyclases (ACs), AC1 and AC8 (DKO), show increased sedation durations and impaired protein kinase A (PKA) phosphorylation following acute ethanol treatment. Therefore, using DKO mice, we compared the neurobehavioral responses following toluene exposure to that of ethanol exposure to determine if these abused substances share molecular mechanisms of action. In the present study, acute sensitivity to toluene- or ethanol-induced changes in locomotor activity was evaluated in DKO and wild type (WT) mice. Mice were exposed to toluene vapor (0, 500, 1000, 2000, 6000, or 8000ppm) for 30min in static exposure chambers equipped with activity monitors. Both WT and DKO mice demonstrated increased ambulatory distance during exposure to a 2000-ppm concentration of toluene compared to respective air-exposed (0ppm) controls. Significant increases in locomotor activity were also observed during an air-only recovery period following toluene exposure in WT and DKO mice that had been exposed to 2000ppm of toluene compared to respective air controls. Sedative effects of toluene were equivalent in WT and DKO mice, both during exposure and afterwards during recovery. Although no significant differences in locomotor activity were detected in DKO compared to WT mice at individual doses tested, a significant main effect of toluene was achieved, with DKO mice demonstrating a generalized reduction in locomotor activity during the post-toluene recovery period compared to WT mice (when analyzing all doses collectively). For comparison to toluene, additional WT and DKO mice were treated with 1.0 or 2.0g/kg ethanol (i.p.) and monitored for locomotor activation. In WT mice, both doses of ethanol increased distance traveled compared to saline controls. Conversely, DKO mice demonstrated no increase in locomotor activation at 1.0g/kg, with significantly reduced distances traveled at both doses compared to ethanol-treated WT mice. These behavioral activity results suggest that acute effects of ethanol and toluene are distinct in the mechanisms by which they induce acute sedating effects with respect to AC1 and AC8 activity, but may be similar in the mechanisms subserving locomotor stimulation.

The propensity for consuming ethanol in Drosophila requires rutabaga adenylyl cyclase expression within mushroom body neurons

Alcohol activates reward systems through an unknown mechanism, in some cases leading to alcohol abuse and dependence. Herein, we utilized a two-choice Capillary Feeder assay to address the neural and molecular basis for ethanol self-administration in Drosophila melanogaster. Wild-type Drosophila shows a significant preference for food containing between 5% and 15% ethanol. Preferred ethanol self-administration does not appear to be due to caloric advantage, nor due to perceptual biases, suggesting a hedonic bias for ethanol exists in Drosophila. Interestingly, rutabaga adenylyl cyclase expression within intrinsic mushroom body neurons is necessary for robust ethanol self-administration. The expression of rutabaga in mushroom bodies is also required for both appetitive and aversive olfactory associative memories, suggesting that reinforced behavior has an important role in the ethanol self-administration in Drosophila. However, rutabaga expression is required more broadly within the mushroom bodies for the preference for ethanol-containing food than for olfactory memories reinforced by sugar reward. Together these data implicate cAMP signaling and behavioral reinforcement for preferred ethanol self-administration in D. melanogaster.

Dantrolene blockade of ryanodine receptor impairs ethanol-induced behavioral stimulation, ethanol intake and loss of righting reflex

Calcium has been characterized as one of the most ubiquitous, universal and versatile intracellular signals. Among other substances with the ability to alter intracellular calcium levels, ethanol has been described as particularly relevant because of its social and economic impact. Ethanol effects on calcium distribution and flux in vitro have been widely studied, showing that acute ethanol administration can modulate intracellular calcium concentrations in a dose dependent manner. Intracellular calcium released from the endoplasmic reticulum plays a determinant role in several cellular processes. In this study, we aim to assess the effect of dantrolene, a ryanodine receptor antagonist, on three different ethanol-elicited behaviors: locomotor activity, loss of righting reflex and ethanol intake. Mice were challenged with an injection of dantrolene (0-5 mg/kg, i.p.) 30 min before ethanol (0-4 g/kg, i.p.) administration. Animals were immediately placed in an open field cylinder to monitor distance travelled horizontally or in a V-shaped trough to measure righting reflex recovery time. For ethanol intake, dantrolene (0-5mg/kg, i.p.) was administered 30 min before ethanol (20%, v/v) exposure, following a drinking in the dark paradigm. Our results showed that dantrolene selectively reduces ethanol-induced stimulation, loss of righting reflex, and ethanol intake in a dose dependent manner. Together, these data suggest that intracellular calcium released from the endoplasmic reticulum may play a critical role in behavioral effects caused by ethanol, and point to a calcium-dependent pathway as a possible cellular mechanism of action for ethanol.

Drosophila melanogaster as a model to study drug addiction

Animal studies have been instrumental in providing knowledge about the molecular and neural mechanisms underlying drug addiction. Recently, the fruit fly Drosophilamelanogaster has become a valuable system to model not only the acute stimulating and sedating effects of drugs but also their more complex rewarding properties. In this review, we describe the advantages of using the fly to study drug-related behavior, provide a brief overview of the behavioral assays used, and review the molecular mechanisms and neural circuits underlying drug-induced behavior in flies. Many of these mechanisms have been validated in mammals, suggesting that the fly is a useful model to understand the mechanisms underlying addiction.

Sex-specific role for adenylyl cyclase type 7 in alcohol dependence

BACKGROUND

Alcohol has been shown to critically modulate cyclic adenosine-3',5' monophosphate (cAMP) signaling. A number of downstream effectors that respond to the cAMP signals (e.g., protein kinase A, cAMP response element binding protein) have, in turn, been examined in relation to alcohol consumption. These studies did not, however, delineate the point at which the actions of alcohol on the cAMP cascade might translate into differences in drinking behavior. To further understand the role of cAMP synthesis in alcohol drinking and dependence, we investigated a specific adenylyl cyclase isoform, adenylyl cyclase (AC) Type 7, whose activity is selectively enhanced by ethanol.

METHODS

We measured alcohol consumption and preference in mice in which one copy of the Adcy7 gene was disrupted (Adcy7(+/-)). To demonstrate relevance of this gene for alcohol dependence in humans, we tested the association of polymorphisms in the ADCY7 gene with alcohol dependence in a sample of 1703 alcohol-dependent individuals and 1347 control subjects.

RESULTS

We show that Adcy7(+/-) female mice have higher preference for alcohol than wild-type mice, whereas there is little difference in alcohol consumption or preference between Adcy7(+/-) male mice and wild-type control subjects. In the human sample, we found that single nucleotide polymorphisms in ADCY7 associate with alcohol dependence in women, and these markers are also associated with ADCY7 expression (messenger RNA) levels.

CONCLUSIONS

These findings implicate adenylyl cyclase Type 7 as a critical component of the molecular pathways contributing to alcohol drinking and the development of alcohol dependence.

Mice lacking adenylyl cyclase type 5 (AC5) show increased ethanol consumption and reduced ethanol sensitivity

RATIONALE

The adenylyl cyclase (AC)/cAMP system is believed to be a key component in regulating alcohol-drinking behavior. It was reported that adenylyl cyclase-5 (AC5) is expressed widely in the brain, with a preferential concentration in the dorsal striatum and nucleus accumbens, brain regions which are important for addiction and emotion. AC5 has been shown to be an essential mediator of morphine addiction and dopamine receptor function; however, it remains unknown whether or not AC5 plays a role in ethanol preference and sensitivity in animals.

OBJECTIVE

This work was carried out to determine the role of AC5 in alcohol consumption and the hypnotic response to alcohol using AC5 knockout (KO) mice.

RESULTS

In the test for ethanol preference employing a two-bottle free-choice paradigm, AC5 KO mice showed increased ethanol consumption and preference compared with the wild-type mice. Ethanol-induced hypothermia was weakly reduced in AC5 KO mice. AC5 KO mice exhibited sedation/behavioral sleep to high-dose ethanol, but their responses were greatly suppressed compared with the wild-type mice.

CONCLUSIONS

These results suggest that AC5 is an important signaling molecule regulating alcohol sensitivity and preference in animals. These data provide critical information for AC5 activation as a candidate target for the treatment of alcoholism.

Molecular targets of alcohol action: Translational research for pharmacotherapy development and screening

Alcohol abuse and dependence are multifaceted disorders with neurobiological, psychological, and environmental components. Research on other complex neuropsychiatric diseases suggests that genetically influenced intermediate characteristics affect the risk for heavy alcohol consumption and its consequences. Diverse therapeutic interventions can be developed through identification of reliable biomarkers for this disorder and new pharmacological targets for its treatment. Advances in the fields of genomics and proteomics offer a number of possible targets for the development of new therapeutic approaches. This brain-focused review highlights studies identifying neurobiological systems associated with these targets and possible pharmacotherapies, summarizing evidence from clinically relevant animal and human studies, as well as sketching improvements and challenges facing the fields of proteomics and genomics. Concluding thoughts on using results from these profiling technologies for medication development are also presented.

Sustained antagonism of acute ethanol-induced ataxia following microinfusion of cyclic AMP and cpt-cAMP in the mouse cerebellum

Ataxia is a conspicuous physical manifestation of alcohol consumption in humans and laboratory animals. Previously we reported possible involvement of cAMP in ethanol-induced ataxia. We now report a sustained antagonism of ataxia due to multiple ethanol injections following intracerebellar (ICB) cAMP or cpt-cAMP microinfusion. Adenylyl cyclase drugs cAMP, cpt-cAMP, Sp-cAMP, Rp-cAMP, adenosine A₁ agonist, N⁶-cyclohexyladenosine (CHA) and GABA(A) agonist muscimol were directly microinfused into the cerebellum of CD-1 male mice to evaluate their effect on ethanol (2 g/kg; i.p.) ataxia. Drug microinfusions were made via stereotaxically implanted stainless steel guide cannulas. Rotorod was used to evaluate the ethanol's ataxic response. Intracerebellar cAMP (0.1, 1, 10 fmol) or cpt-cAMP (0.5, 1, 2 fmol) 60 min before ethanol treatment, dose-dependently attenuated ethanol-induced ataxia in general agreement with previous observations. Intracerebellar microinfusion of cAMP (100 fmol) or cpt-cAMP (2 fmol) produced a sustained attenuation of ataxia following ethanol administration at 1, 4, 7 and 25 h or 31 h post-cAMP/cpt-cAMP microinfusion. At 31 h post-cAMP, the ataxic response of ethanol reappeared. Additionally, marked antagonism to the accentuation of ethanol-induced ataxia by adenosine A₁ and GABA(A) agonists, CHA (34 pmol) and muscimol (88 pmol), respectively, was noted 24h after cAMP and cpt-cAMP treatment. This indicated possible participation of AC/cAMP/PKA signaling in the co-modulation of ethanol-induced ataxia by A₁ adenosinergic and GABAergic systems. No change in normal motor coordination was noted when cAMP or cpt-cAMP microinfusion was followed by saline. Finally, Rp-cAMP (PKA inhibitor, 22 pmol) accentuated ethanol-induced ataxia and antagonized its attenuation by cAMP whereas Sp-cAMP (PKA activator, 22 pmol) produced just the opposite effects, further indicating participation of cAMP-dependent PKA downstream. Overall, the results support a role of AC/cAMP/PKA signaling in the expression of ethanol-induced ataxia and its co-modulation by adenosine A₁ and GABA(A) receptors.

Neuroprotective effect of vitamin C against the ethanol and nicotine modulation of GABA(B) receptor and PKA-alpha expression in prenatal rat brain

Prenatal ethanol exposure has various deleterious effects on neuronal development and can induce various defects in developing brain, resulting in fetal alcohol syndrome (FAS). gamma-Aminobutyric acid (GABA(B)) receptor (R) is known to play an important role during the development of the central nervous system (CNS). Our study was designed to investigate the effect of ethanol (100 mM), nicotine (50 microM) (for 30 min and 1 h), vitamin C (vitC, 0.5 mM), ethanol plus vitC, and nicotine plus vitC on expression level of GABA(B1), GABA(B2)R, and protein kinase A-alpha (PKA) in prenatal rat cortical and hippocampal neurons at gestational days (GD) 17.5. The results showed that, upon ethanol and nicotine exposure, GABA(B1) and GABA(B2)R protein expression increased significantly in the cortex and hippocampus for a short (30 min) and long term (1 h), whereas only GABA(B2)R subunit was decreased upon nicotine exposure for a long term in the cortex. Furthermore, PKA expression in cortex and hippocampus increased with ethanol exposure during short term, whereas long-term exposure results increased in cortex and decreased in hippocampus. Moreover, the cotreatment of vitC with ethanol and nicotine showed significantly decreased expression of GABA(B1), GABA(B2)R, and PKA in cortex and hippocampus for a long-term exposure. Mitochondrial membrane potential, Fluoro-jade-B, and propidium iodide staining were used to elucidate possible neurodegeneration. Our results suggest the involvement of GABA(B)R and PKA in nicotine and ethanol-mediated neurodevelopmental defects and the potential use of vitC as a effective protective agent for FAS-related deficits.

Adenylyl cyclases 1 and 8 initiate a presynaptic homeostatic response to ethanol treatment

BACKGROUND

Although ethanol exerts widespread action in the brain, only recently has progress been made in understanding the specific events occurring at the synapse during ethanol exposure. Mice deficient in the calcium-stimulated adenylyl cyclases, AC1 and AC8 (DKO), demonstrate increased sedation duration and impaired phosphorylation by protein kinase A (PKA) following acute ethanol treatment. While not direct targets for ethanol, we hypothesize that these cyclases initiate a homeostatic presynaptic response by PKA to reactivate neurons from ethanol-mediated inhibition.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we have used phosphoproteomic techniques and identified several presynaptic proteins that are phosphorylated in the brains of wild type mice (WT) after ethanol exposure, including synapsin, a known PKA target. Phosphorylation of synapsins I and II, as well as phosphorylation of non-PKA targets, such as, eukaryotic elongation factor-2 (eEF-2) and dynamin is significantly impaired in the brains of DKO mice. This deficit is primarily driven by AC1, as AC1-deficient, but not AC8-deficient mice also demonstrate significant reductions in phosphorylation of synapsin and eEF-2 in cortical and hippocampal tissues. DKO mice have a reduced pool of functional recycling vesicles and fewer active terminals as measured by FM1-43 uptake compared to WT controls, which may be a contributing factor to the impaired presynaptic response to ethanol treatment.

CONCLUSIONS/SIGNIFICANCE

These data demonstrate that calcium-stimulated AC-dependent PKA activation in the presynaptic terminal, primarily driven by AC1, is a critical event in the reactivation of neurons following ethanol-induced activity blockade.

Phosphorylation of GluR1, ERK, and CREB during spontaneous withdrawal from chronic heroin self-administration

Negative motivational symptoms are observed soon after withdrawal from chronic opiate administration, and are thought to mediate dependence. Examination of brain region-specific signaling changes that accompany early withdrawal may shed light on neural mechanisms underlying negative reinforcement and dependence. Thus, we measured alterations in protein phosphorylation in multiple limbic brain regions in rats undergoing 24 h spontaneous or naltrexone-precipitated withdrawal from chronic (6 h/day) i.v. heroin self-administration. Region-specific increases in cyclic AMP-dependent GluR(1) (S845) phosphorylation were found in the nucleus accumbens shell, basolateral amygdala, hippocampal CA1 and CA3 subregions, and premotor cortex from 12 to 24 h of spontaneous withdrawal, and there were no changes in prefrontal cortex, nucleus accumbens core or caudate-putamen. Increased GluR(1) (S845) phosphorylation was detected earlier (12 h withdrawal) in the central amygdala and ventral tegmental area. In contrast, prominent increases in extracellular signal-regulated kinase phosphorylation were found in both prefrontal and premotor cortex, and CA1 and CA3 between 12 and 24 h withdrawal. Phosphorylation of striatal cyclic AMP response element binding protein increased in the caudate-putamen but not in the nucleus accumbens. Naltrexone administration after 24 h withdrawal increased extracellular signal-regulated kinase phosphorylation in the central amygdala, and nucleus accumbens core and shell. Thus, spontaneous withdrawal from heroin self-administration produces region- and time-dependent changes in cyclic AMP and extracellular signal-regulated kinase activity that could contribute to the behavioral manifestation of opiate dependence.