Dutasteride reduces alcohol's sedative effects in men in a human laboratory setting and reduces drinking in the natural environment

Novel medications for problematic alcohol use

Alcohol-related harm, a major cause of disease burden globally, affects people along a spectrum of use. When a harmful pattern of drinking is present in the absence of significant behavioral pathology, low-intensity brief interventions that provide information about health consequences of continued use provide large health benefits. At the other end of the spectrum, profound behavioral pathology, including continued use despite knowledge of potentially fatal consequences, warrants a medical diagnosis, and treatment is strongly indicated. Available behavioral and pharmacological treatments are supported by scientific evidence but are vastly underutilized. Discovery of additional medications, with a favorable balance of efficacy versus safety and tolerability can improve clinical uptake of treatment, allow personalized treatment, and improve outcomes. Here, we delineate the clinical conditions when pharmacotherapy should be considered in relation to the main diagnostic systems in use and discuss clinical endpoints that represent meaningful clinical benefits. We then review specific developments in three categories of targets that show promise for expanding the treatment toolkit. GPCRs remain the largest category of successful drug targets across contemporary medicine, and several GPCR targets are currently pursued for alcohol-related indications. Endocrine systems are another established category, and several promising targets have emerged for alcohol indications. Finally, immune modulators have revolutionized treatment of multiple medical conditions, and they may also hold potential to produce benefits in patients with alcohol problems.

Randomized Placebo-Controlled Clinical Trial of Dutasteride for Reducing Heavy Drinking in Men

BACKGROUND

Prior studies indicate that neuroactive steroids mediate some of alcohol's effects. Dutasteride, widely used to treat benign prostatic hypertrophy, is an inhibitor of 5-alpha reductase enzymes, which play a central role in the production of 5α-reduced neuroactive steroids. The purpose of this study was to test dutasteride's tolerability and efficacy for reducing drinking.

METHODS

Men (n = 142) with heavy drinking (>24 drinks per week) and a goal to either stop or reduce drinking to nonhazardous levels were randomized to placebo or 1 mg dutasteride daily for 12 weeks. We hypothesized that dutasteride-treated patients would be more successful in reducing drinking.

RESULTS

Generalized linear mixed models that included baseline drinking, treatment, time and their 2-way interaction identified significant interactions of treatment-time, such that dutasteride treatment reduced drinking more than placebo. During the last month of treatment, 25% of dutasteride-treated participants had no hazardous drinking (no heavy drinking days and not more than 14 drinks per week) compared with 6% of placebo-treated participants (P = 0.006; NNT = 6). Sensitivity analysis identified baseline drinking to cope as a factor associated with larger reductions in drinking for dutasteride compared with placebo-treated participants. Dutasteride was well tolerated. Adverse events more common in the dutasteride group were stomach discomfort and reduced libido.

CONCLUSION

Dutasteride 1 mg daily was efficacious in reducing the number of heavy drinking days and drinks per week in treatment-seeking men. The benefit of dutasteride compared with placebo was greatest for participants with elevated baseline drinking to cope motives.

Investigating genetically stratified subgroups to better understand the etiology of alcohol misuse

Alcohol misuse (AM) is highly prevalent and harmful, with theorized subgroups differing on internalizing and externalizing dimensions. Despite known heterogeneity, genome-wide association studies (GWAS) are usually conducted on unidimensional phenotypes. These approaches have identified important genes related to AM but fail to capture a large part of the heritability, even with recent increases in sample sizes. This study aimed to address phenotypic heterogeneity in GWAS to aid gene finding and to uncover the etiology of different types of AM. Genetic and phenotypic data from 410,414 unrelated individuals of multiple ancestry groups (primarily European) in the UK Biobank were obtained. Mixture modeling was applied to measures of alcohol misuse and internalizing/externalizing psychopathology to uncover phenotypically homogenous subclasses, which were carried forward to GWAS and functional annotation. A four-class model emerged with "low risk", "internalizing-light/non-drinkers", "heavy alcohol use-low impairment", and "broad high risk" classes. SNP heritability ranged from 3 to 18% and both known AM signals and novel signals were captured by genomic risk loci. Class comparisons showed distinct patterns of regional brain tissue enrichment and genetic correlations with internalizing and externalizing phenotypes. Despite some limitations, this study demonstrated the utility of genetic research on homogenous subclasses. Not only were novel genetic signals identified that might be used for follow-up studies, but addressing phenotypic heterogeneity allows for the discovery and investigation of differential genetic vulnerabilities in the development of AM, which is an important step towards the goal of personalized medicine.

A Review of the Characteristics of Clinical Trials and Potential Medications for Alcohol Dependence: Data Analysis from ClinicalTrials.gov

Objective. This study provides a comprehensive analysis of the characteristics of clinical trials related to alcohol dependence that are registered on ClinicalTrials.gov. Methods. All ClinicalTrials.gov trials registered up to 1 January 2023 were examined, focusing on trials that involved alcohol dependence. All 1295 trials were summarized by presenting their characteristics and results and reviewed most intervention drugs used in the treatment of alcohol dependence. Results. The study analysis identified a total of 1295 clinical trials registered on ClinicalTrials.gov that were focused on alcohol dependence. Of these, 766 trials had been completed, representing 59.15% of the total, while 230 trials were currently recruiting participants, accounting for 17.76% of the total. None of the trials had yet been approved for marketing. The majority of the studies included in this analysis were interventional studies (1145 trials, or 88.41%), which accounted for most of the patients enrolled in the trials. In contrast, observational studies represented only a small portion of the trials (150 studies, or 11.58%) and involved a smaller number of patients. In terms of geographic distribution, the majority of registered studies were located in North America (876 studies, or 67.64%), while only a small number of studies were registered in South America (7 studies, or 0.54%). Conclusions. The purpose of this review is to provide a basis for the treatment of alcohol dependence and prevention of its onset through an overview of clinical trials registered at ClinicalTrials.gov. It also offers essential information for future research to guide future studies.

Immune treatments for alcohol use disorder: A translational framework

While the immune system is essential for survival, an excessive or prolonged inflammatory response, such as that resulting from sustained heavy alcohol use, can damage the host and contribute to psychiatric disorders. A growing body of literature indicates that the immune system plays a critical role in the development and maintenance of alcohol use disorder (AUD). As such, there is enthusiasm for treatments that can restore healthy levels of inflammation as a mechanism to reduce drinking and promote recovery. In this qualitative literature review, we provide a conceptual rationale for immune therapies and discuss progress in medications development for AUD focused on the immune system as a treatment target. This review is organized into sections based on primary signaling pathways targeted by the candidate therapies, namely: (a) toll-like receptors, (b) phosphodiesterase inhibitors, (c) peroxisome proliferator-activated receptors, (d) microglia and astrocytes, (e) other immune pharmacotherapies, and (f) behavioral therapies. As relevant within each section, we examine the basic biological mechanisms of each class of therapy and evaluate preclinical research testing the role of the therapy on mitigating alcohol-related behaviors in animal models. To the extent available, translational findings are reviewed with discussion of completed and ongoing randomized clinical trials and their findings to date. An applied and clinically focused approach is taken to identify the potential clinical applications of the various treatments reviewed. We conclude by delineating the most promising candidate treatments and discussing future directions by considering opportunities for immune treatment development and personalized medicine for AUD.

A Critical Review of Alcohol Administration Guidelines in Laboratory Medication Screening Research: Is It Time to Include Treatment Seekers?

Human laboratory studies play an important role in alcohol use disorder (AUD) medication development. Medications that are found to be safe and effective during human laboratory screening will then move to more expensive clinical trials in patient populations. Given the gatekeeping role of human laboratory studies in the medication development pipeline, it is critical that these studies accurately forecast how pharmacotherapies will perform under true-to-life clinical conditions. On the other hand, the design of these studies also must adhere to ethical guidelines: certain aspects of clinical reality cannot be incorporated into screening studies because doing so might place the participant at risk for harm or breach other ethical guidelines. Conventions exist that guide the resolution of these conflicting ideals. This article considers the practice of recruiting non-treatment-seeking heavy drinkers to participate in laboratory screening studies. By convention, volunteers are excluded from laboratory screening studies that involve alcohol administration if they are deemed "treatment seeking," meaning that they recently stopped drinking or are motivated to do so. Although this common practice may reduce risk to participants, findings may not accurately predict medication effects on treatment seekers. Indeed, there is empirical evidence that treatment seekers differ from nontreatment seekers in their responses to medications (Neuropsychopharmacology 2017a; 42: 1776; Am J Drug Alcohol Abuse 2017b; 43: 703; J Psychiatr Res 2006; 40: 383). Here, we argue for the importance of recruiting treatment seekers for this research due to their qualitative difference from nontreatment seekers. We argue that these individuals should be the default population in human laboratory medication screening studies. We conclude by discussing 2 case examples of medication experiments led by our research groups that involved administering medications to treatment seekers.

Molecular Correlates of Topiramate and GRIK1 rs2832407 Genotype in Pluripotent Stem Cell-Derived Neural Cultures

BACKGROUND

There is growing evidence that the anticonvulsant topiramate is efficacious in reducing alcohol consumption. Further, an intronic single nucleotide polymorphism (rs2832407, C A) in the GRIK1 gene, which encodes the GluK1 subunit of the excitatory kainate receptor, predicted topiramate's effectiveness in reducing heavy drinking in a clinical trial. The molecular correlates of GRIK1 genotype that may relate to topiramate's ability to reduce drinking remain unknown.

METHODS

We differentiated induced pluripotent stem cells (iPSCs) characterized by GRIK1 rs2832407 genotype from 8 A/A and 8 C/C donors into forebrain-lineage neural cultures. Our differentiation protocol yielded mixed neural cultures enriched for glutamatergic neurons. Basal mRNA expression of the GRIK1 locus was examined via quantitative polymerase chain reaction (qPCR). The effects of acute topiramate exposure on excitatory spontaneous synaptic activity were examined via whole-cell patch-clamp electrophysiology. Results were compared and contrasted between iPSC donor genotypes.

RESULTS

Although characterization of the GRIK1 locus revealed no effect of rs2832407 genotype on GRIK1 isoform mRNA expression, a significant difference was observed on GRIK1 antisense-2 expression, which was greater in C/C neural cultures. Differential effects of acute exposure to 5 μM topiramate were observed on spontaneous synaptic activity in A/A versus C/C neurons, with a smaller reduction in excitatory event frequency observed in C/C donor neurons.

CONCLUSIONS

This work highlights the use of iPSC technologies to study pharmacogenetic treatment effects in psychiatric disorders and furthers our understanding of the molecular effects of topiramate exposure in human neural cells.

Effect of alcohol on blood pressure

BACKGROUND

Alcohol is consumed by over 2 billion people worldwide. It is a common substance of abuse and its use can lead to more than 200 disorders including hypertension. Alcohol has both acute and chronic effects on blood pressure. This review aimed to quantify the acute effects of different doses of alcohol over time on blood pressure and heart rate in an adult population.

OBJECTIVES

Primary objective To determine short-term dose-related effects of alcohol versus placebo on systolic blood pressure and diastolic blood pressure in healthy and hypertensive adults over 18 years of age. Secondary objective To determine short-term dose-related effects of alcohol versus placebo on heart rate in healthy and hypertensive adults over 18 years of age.

SEARCH METHODS

The Cochrane Hypertension Information Specialist searched the following databases for randomised controlled trials up to March 2019: the Cochrane Hypertension Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 2), in the Cochrane Library; MEDLINE (from 1946); Embase (from 1974); the World Health Organization International Clinical Trials Registry Platform; and ClinicalTrials.gov. We also contacted authors of relevant articles regarding further published and unpublished work. These searches had no language restrictions.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing effects of a single dose of alcohol versus placebo on blood pressure (BP) or heart rate (HR) in adults (≥ 18 years of age).

DATA COLLECTION AND ANALYSIS

Two review authors (ST and CT) independently extracted data and assessed the quality of included studies. We also contacted trial authors for missing or unclear information. Mean difference (MD) from placebo with 95% confidence interval (CI) was the outcome measure, and a fixed-effect model was used to combine effect sizes across studies.  MAIN RESULTS: We included 32 RCTs involving 767 participants. Most of the study participants were male (N = 642) and were healthy. The mean age of participants was 33 years, and mean body weight was 78 kilograms. Low-dose alcohol (< 14 g) within six hours (2 RCTs, N = 28) did not affect BP but did increase HR by 5.1 bpm (95% CI 1.9 to 8.2) (moderate-certainty evidence). Medium-dose alcohol (14 to 28 g) within six hours (10 RCTs, N = 149) decreased systolic blood pressure (SBP) by 5.6 mmHg (95% CI -8.3 to -3.0) and diastolic blood pressure (DBP) by 4.0 mmHg (95% CI -6.0 to -2.0) and increased HR by 4.6 bpm (95% CI 3.1 to 6.1) (moderate-certainty evidence for all).  Medium-dose alcohol within 7 to 12 hours (4 RCTs, N = 54) did not affect BP or HR. Medium-dose alcohol > 13 hours after consumption (4 RCTs, N = 66) did not affect BP or HR. High-dose alcohol (> 30 g) within six hours (16 RCTs, N = 418) decreased SBP by 3.5 mmHg (95% CI -6.0 to -1.0), decreased DBP by 1.9 mmHg (95% CI-3.9 to 0.04), and increased HR by 5.8 bpm (95% CI 4.0 to 7.5). The certainty of evidence was moderate for SBP and HR, and was low for DBP. High-dose alcohol within 7 to 12 hours of consumption (3 RCTs, N = 54) decreased SBP by 3.7 mmHg (95% CI -7.0 to -0.5) and DBP by 1.7 mmHg (95% CI -4.6 to 1.8) and increased HR by 6.2 bpm (95% CI 3.0 to 9.3). The certainty of evidence was moderate for SBP and HR, and low for DBP. High-dose alcohol ≥ 13 hours after consumption (4 RCTs, N = 154) increased SBP by 3.7 mmHg (95% CI 2.3 to 5.1), DBP by 2.4 mmHg (95% CI 0.2 to 4.5), and HR by 2.7 bpm (95% CI 0.8 to 4.6) (moderate-certainty evidence for all).  AUTHORS' CONCLUSIONS: High-dose alcohol has a biphasic effect on BP; it decreases BP up to 12 hours after consumption and increases BP > 13 hours after consumption. High-dose alcohol increases HR at all times up to 24 hours. Findings of this review are relevant mainly to healthy males, as only small numbers of women were included in the included trials.

Physiopathological role of the enzymatic complex 5α-reductase and 3α/β-hydroxysteroid oxidoreductase in the generation of progesterone and testosterone neuroactive metabolites

The enzymatic complex 5α-reductase (5α-R) and 3α/3β-hydroxysteroid oxidoreductase (HSOR) is expressed in the nervous system, where it transforms progesterone (PROG) and testosterone (T) into neuroactive metabolites. These metabolites regulate myelination, brain maturation, neurotransmission, reproductive behavior and the stress response. The expression of 5α-R and 3α-HSOR and the levels of PROG and T reduced metabolites show regional and sex differences in the nervous system and are affected by changing physiological conditions as well as by neurodegenerative and psychiatric disorders. A decrease in their nervous tissue levels may negatively impact the course and outcome of some pathological events. However, in other pathological conditions their increased levels may have a negative impact. Thus, the use of synthetic analogues of these steroids or 5α-R modulation have been proposed as therapeutic approaches for several nervous system pathologies. However, further research is needed to fully understand the consequences of these manipulations, in particular with 5α-R inhibitors.

The Human Laboratory and Drug Development in Alcohol Use Disorder: Recent Updates

Despite a number of approved medications for alcohol use disorder (AUD), this chronic relapsing disease still produces a considerable global burden, with both health-related and financial consequences. While clinical trials are a critical step in drug development, human laboratory studies provide the field with means of screening pharmacotherapy for more nuanced aspects of AUD. Specifically, studies employing alcohol administration techniques (e.g., alcohol challenge and self-administration) are able to investigate potential drugs with respect to their ability to alter various responses to alcohol administration or alter alcohol consumption in laboratory settings. This chapter reviews methodological designs and provides updates from alcohol administration studies used to screen for potential AUD pharmacotherapy over the past decade. These recent studies have supported the efficacy of approved drugs, identified some promising novel drugs, and investigated other drugs that appear ineffective in AUD treatment. Yet, few drugs are explored using the different variants of alcohol administration methods, and using the different methods has provided inconsistent results for the same drug. Future research would aid advancement in the field by testing medication with various methodologies and refining recently developed techniques.

Alcohol Tolerance in Human Laboratory Studies for Development of Medications to treat Alcohol Use Disorder

AIMS

Human laboratory studies have contributed extensively in the research and development of novel medications to treat alcohol use disorder (AUD). Alcohol tolerance may represent one additional variable that can be utilized to expand the understanding of the AUD wide phenotypic profile and provide support to the medication development process. Tolerance is characterized as an individual's subjective response to alcohol and has been recognized as a predictor of AUD progression. Tolerance can be evaluated both by self-reported response (e.g. assessments) and objective measurements (e.g. motor impairment); as such, it represents an exploitable variable in the field of alcohol research.

METHODS

This Narrative Review focuses on the use of alcohol tolerance, specifically within alcohol laboratory studies, for medication development. It seeks to identify a research gap and a research opportunity in clinical studies to evaluate biobehavioral responses captured in order to develop medications to treat AUD.

RESULTS

Alcohol tolerance may provide additional information on the safety and tolerability of medications to treat AUD, in particular, when novel medications are co-administered with alcohol within the AUD population.

CONCLUSIONS

As such, alcohol tolerance represents an additional outcome that may be included in randomized clinical trial (RCT) protocols designed for developing AUD pharmacotherapies.

Sex differences in steroid levels and steroidogenesis in the nervous system: Physiopathological role

The nervous system, in addition to be a target for steroid hormones, is the source of a variety of neuroactive steroids, which are synthesized and metabolized by neurons and glial cells. Recent evidence indicates that the expression of neurosteroidogenic proteins and enzymes and the levels of neuroactive steroids are different in the nervous system of males and females. We here summarized the state of the art of neuroactive steroids, particularly taking in consideration sex differences occurring in the synthesis and levels of these molecules. In addition, we discuss the consequences of sex differences in neurosteroidogenesis for the function of the nervous system under healthy and pathological conditions and the implications of neuroactive steroids and neurosteroidogenesis for the development of sex-specific therapeutic interventions.

Stress and drug abuse-related disorders: The promising therapeutic value of neurosteroids focus on pregnenolone-progesterone-allopregnanolone pathway

The pregnenolone-progesterone-allopregnanolone pathway is receiving increasing attention in research on the role of neurosteroids in pathophysiology, particularly in stress-related and drug use disorders. These disorders involve an allostatic change that may result from deficiencies in allostasis or adaptive responses, and may be downregulated by adjustments in neurotransmission by neurosteroids. The following is an overview of findings that assess how pregnenolone and/or allopregnanolone concentrations are altered in animal models of stress and after consumption of alcohol or cannabis-type drugs, as well as in patients with depression, anxiety, post-traumatic stress disorder or psychosis and/or in those diagnosed with alcohol or cannabis use disorders. Preclinical and clinical evidence shows that pregnenolone and allopregnanolone, operating according to a different or common pharmacological profile involving GABAergic and/or endocannabinoid system, may be relevant biomarkers of psychiatric disorders for therapeutic purposes. Hence, ongoing clinical trials implicate synthetic analogs of pregnenolone or allopregnanolone, and also modulators of neurosteroidogenesis.

Dynamic Adaptation in Neurosteroid Networks in Response to Alcohol

The term neurosteroid refers to rapid membrane actions of steroid hormones and their derivatives that can modulate physiological functions and behavior via their interactions with ligand-gated ion channels. This chapter will highlight recent advances pertaining to the modulatory effects of a select group of neurosteroids that are primarily potent positive allosteric modulators of γ-aminobutyric acid_A receptors (GABA_ARs). Nanomolar concentrations of neurosteroids, which occur in vivo, potentiate phasic and tonic forms of GABA_AR-mediated inhibition, indicating that both synaptic and extrasynaptic GABA_ARs possess sensitivity to neurosteroids and contribute to the overall ability of neurosteroids to modulate central nervous system excitability. Common effects of alcohol and neurosteroids at GABA_ARs have stimulated research on the ability of neurosteroids to modulate alcohol's acute and chronic effects. Background on neurosteroid pharmacology and biosynthetic enzymes will be provided as it relates to experimental findings. Data will be summarized on alcohol and neurosteroid interactions across neuroanatomical regions and models of intoxication, consumption, dependence, and withdrawal. Evidence supports independent regulation of neurosteroid synthesis between periphery and brain as well as across brain regions following acute alcohol administration and during withdrawal. Local mechanisms for fine-tuning neuronal excitability via manipulation of neurosteroid synthesis exert predicted behavioral and electrophysiological responses on GABA_AR-mediated inhibition. Collectively, targeting neurosteroidogenesis may be a beneficial treatment strategy for alcohol use disorders.

Alcohol-responsive genes identified in human iPSC-derived neural cultures

Alcohol use contributes to numerous diseases and injuries. The nervous system is affected by alcohol in diverse ways, though the molecular mechanisms of these effects are not clearly understood. Using human-induced pluripotent stem cells (iPSCs), we developed a neural cell culture model to identify the mechanisms of alcohol's effects. iPSCs were generated from fibroblasts and differentiated into forebrain neural cells cultures that were treated with 50 mM alcohol or sham conditions (same media lacking alcohol) for 7 days. We analyzed gene expression using total RNA sequencing (RNA-seq) for 34 samples derived from 10 subjects and for 10 samples from 5 subjects in an independent experiment that had intermittent exposure to the same dose of alcohol. We also analyzed genetic effects on gene expression and conducted a weighted correlation network analysis. We found that differentiated neural cell cultures have the capacity to recapitulate gene regulatory effects previously observed in specific primary neural tissues and identified 226 genes that were differentially expressed (FDR < 0.1) after alcohol treatment. The effects on expression included decreases in INSIG1 and LDLR, two genes involved in cholesterol homeostasis. We also identified a module of 58 co-expressed genes that were uniformly decreased following alcohol exposure. The majority of these effects were supported in independent alcohol exposure experiments. Enrichment analysis linked the alcohol responsive genes to cell cycle, notch signaling, and cholesterol biosynthesis pathways, which are disrupted in several neurological disorders. Our findings suggest that there is convergence between these disorders and the effects of alcohol exposure.

Genotype Differences in Sensitivity to the Anticonvulsant Effect of the Synthetic Neurosteroid Ganaxolone during Chronic Ethanol Withdrawal

Sensitivity to anticonvulsant effects of the γ-aminobutyric acid_A receptor-active neurosteroid allopregnanolone (ALLO) during ethanol withdrawal varies across genotypes, with high sensitivity in genotypes with mild withdrawal and low sensitivity in genotypes with high withdrawal. The present studies determined whether the resistance to ALLO during withdrawal in mouse genotypes with high handling-induced convulsions (HICs) during withdrawal could be overcome with use of ganaxolone (GAN), the metabolically stable derivative of ALLO. In separate studies, male and female Withdrawal Seizure-Prone (WSP-1) and DBA/2J (D2) mice were exposed to air (controls) or 72-h ethanol vapor and then were scored for HICs during withdrawal (hourly for the first 12 h, then at hours 24 and 25). After the HIC scoring at hours 5 and 9, mice were injected with 10 mg/kg GAN or vehicle. Area under the HIC curve (AUC) for hours 5-12 was analyzed. In control WSP-1 mice, GAN significantly reduced AUC by 52% (males) and 63% (females), with effects that were absent or substantially reduced during withdrawal. In contrast, GAN significantly reduced AUC in both control and ethanol-withdrawing male and female D2 mice. AUC was decreased by 81% (males) and 70% (females) in controls and by 35% (males) and 21% (females) during withdrawal. The significant anticonvulsant effect of GAN during withdrawal in D2 but not WSP-1 mice suggests that different mechanisms may contribute to ALLO insensitivity during withdrawal in these two genotypes. Importantly, the results in D2 mice suggest that GAN may be a useful treatment for ethanol withdrawal-induced seizures.

GABAA receptor polymorphisms in alcohol use disorder in the GWAS era

Alcohol use disorder (AUD) is a chronic, relapsing, neuro-psychiatric illness of high prevalence and with a serious public health impact worldwide. It is complex and polygenic, with a heritability of about 50%, and influenced by environmental causal heterogeneity. Risk factors associated with its etiology have a genetic component. GABA (γ-aminobutyric acid) is a major inhibitory neurotransmitter in mammalian brain. GABA_A receptors are believed to mediate some of the physiological and behavioral actions of alcohol. In this critical review, relevant genetic terms and type and methodology of the genetic studies are briefly explained. Postulated candidate genes that encode subunits of GABA_A receptors, with all the reported SNPs, are presented. Genetic studies and meta-analyses examining polymorphisms of the GABA_A receptor and their association with AUD predisposition are presented. The data are critically examined with reference to recent GWAS studies that failed to show relations between GABA_A receptors and AUD. Restrictions and perspectives of the different findings are discussed.

Examining the effects of alcohol on GABAA receptor mRNA expression and function in neural cultures generated from control and alcohol dependent donor induced pluripotent stem cells

Factors influencing the development of alcohol-use disorder (AUD) are complex and heterogeneous. While animal models have been crucial to identifying actions of alcohol on neural cells, human-derived in vitro systems that reflect an individual's genetic background hold promise in furthering our understanding of the molecular and functional effects of alcohol exposure and the pathophysiology of AUD. In this report, we utilized induced pluripotent stem cell (iPSCs)-derived neural cell cultures obtained from healthy individuals (CTLs) and those with alcohol dependence (ADs) to 1) examine the effect of 21-day alcohol exposure on mRNA expression of three genes encoding GABAA receptor subunits (GABRA1, GABRG2, and GABRD) using quantitative PCR, and 2) examine the effect of acute and chronic alcohol exposure on GABA-evoked currents using whole-cell patch-clamp electrophysiology. iPSCs from CTLs and ADs were differentiated into neural cultures enriched for forebrain-type excitatory glutamate neurons. Following 21-day alcohol exposure, significant treatment effects were observed in GABRA1, GABRG2, and GABRD mRNA expression. A modestly significant interaction between treatment and donor phenotype was observed for GABRD, which was increased in cell cultures derived from ADs. No effect of acute or chronic alcohol was observed on GABA-evoked currents in neurons from either CTLs or ADs. This work extends findings examining the effects of alcohol on the GABAA receptor in human cell in vitro model systems.

GRIK1 and GABRA2 Variants Have Distinct Effects on the Dose-Related Subjective Response to Intravenous Alcohol in Healthy Social Drinkers

BACKGROUND

The heritable risk for alcohol use disorder (AUD) is expressed partly through alterations in subjective alcohol response. In this study, we investigated the effects of 2 AUD-risk-associated single nucleotide polymorphisms, GABRA2 rs279858 and GRIK1 rs2832407, on the subjective response to alcohol administered intravenously to healthy social drinkers in a laboratory setting.

METHODS

In total, 93 self-identified European American social drinkers underwent 3 blinded laboratory sessions in which they received intravenous infusions of ethanol at 3 target blood alcohol levels (0.00 mg%, 40 mg%, and 100 mg%) using a "clamp" procedure. The self-reported Biphasic Alcohol Effects Scale (BAES) stimulation and sedation subscales were the primary outcome measures. We examined the effects of these 2 genetic variants on subjective response to alcohol.

RESULTS

For the BAES stimulation subscale scores, adjusting for age, baseline scores, and time effects, individuals with 2 copies of the GABRA2 rs279858 C "risk" allele for AUD exhibited the greatest stimulant responses to high-dose alcohol compared to the other risk allele counts (dose-by-allele count interaction effect, p = 0.001, post hoc contrast for C-allele, p = 0.012). For the BAES sedation subscale scores, adjusting for the same covariates, we detected a dose-by-allele count interaction effect (p = 0.0044) such that subjects with 2 copies of the GRIK1 C "risk" allele reported the greatest sedative response to the higher alcohol dose.

CONCLUSIONS

This study suggests that gene variants contributing to the risk for AUD may alter features of the alcohol dose-response relationship in specific ways. GABRA2 rs279858*C enhances stimulant responses to higher levels of alcohol, while the GRIK1 rs2832407*C-allele increases sedative responses. In summary, GRIK1 and GABRA2 variants have distinct effects on the dose-related subjective response to intravenous alcohol in humans.

Medications development for the treatment of alcohol use disorder: insights into the predictive value of animal and human laboratory models

Development of effective treatments for alcohol use disorder (AUD) represents an important public health goal. This review provides a summary of completed preclinical and clinical studies testing pharmacotherapies for the treatment of AUD. We discuss opportunities for improving the translation from preclinical findings to clinical trial outcomes, focusing on the validity and predictive value of animal and human laboratory models of AUD. Specifically, while preclinical studies of medications development have offered important insights into the neurobiology of the disorder and alcohol's molecular targets, limitations include the lack of standardized methods and streamlined processes whereby animal studies can readily inform human studies. Behavioral pharmacology studies provide a less expensive and valuable opportunity to assess the feasibility of a pharmacotherapy prior to initiating larger scale clinical trials by providing insights into the mechanism of the drug, which can then inform recruitment, analyses, and assessments. Summary tables are provided to illustrate the wide range of preclinical, human laboratory, and clinical studies of medications development for alcoholism. Taken together, this review highlights the challenges associated with animal paradigms, human laboratory studies, and clinical trials with the overarching goal of advancing treatment development and highlighting opportunities to bridge the gap between preclinical and clinical research.

Voluntary ethanol consumption reduces GABAergic neuroactive steroid (3α,5α)3-hydroxypregnan-20-one (3α,5α-THP) in the amygdala of the cynomolgus monkey

Neuroactive steroids such as (3α,5α)3-hydroxypregnan-20-one (3α,5α-THP, allopregnanolone) enhance the gamma-aminobutyric acid (GABA)-ergic effects of ethanol and modulate excessive drinking in rodents. Moreover, chronic ethanol consumption reduces 3α,5α-THP levels in human plasma, rat hippocampus and mouse limbic regions. We explored the relationship between 3α,5α-THP levels in limbic brain areas and voluntary ethanol consumption in the cynomolgus monkey following daily self-administration of ethanol for 12 months and further examined the relationship to hypothalamic-pituitary-adrenal (HPA) axis function prior to ethanol exposure. Monkeys were subjected to scheduled induction of ethanol consumption followed by free access to ethanol or water for 22 h/day over 12 months. Immunohistochemistry was performed using an anti-3α,5α-THP antibody. Prolonged voluntary drinking resulted in individual differences in ethanol consumption that ranged from 1.2 to 4.2 g/kg/day over 12 months. Prolonged ethanol consumption reduced cellular 3α,5α-THP immunoreactivity by 13 ± 2 percent (P < 0.05) in the lateral amygdala and 17 ± 2 percent (P < 0.05) in the basolateral amygdala. The effect of ethanol was most pronounced in heavy drinkers that consumed ≥3 g/kg ≥ 20 percent of days. Consequently, 3α,5α-THP immunoreactivity in both the lateral and basolateral amygdala was inversely correlated with average daily ethanol intake (Spearman r = -0.87 and -0.72, respectively, P < 0.05). However, no effect of ethanol and no correlation between drinking and 3α,5α-THP immunoreactivity were observed in the basomedial amygdala. 3α,5α-THP immunoreactivity following ethanol exposure was also correlated with HPA axis function prior to ethanol exposure. These data indicate that voluntary ethanol drinking reduces amygdala levels of 3α,5α-THP in non-human primates and that amygdala 3α,5α-THP levels may be linked to HPA axis function.

Cellular GABAergic Neuroactive Steroid (3α,5α)-3-Hydroxy-Pregnan-20-One (3α,5α-THP) Immunostaining Levels Are Increased in the Ventral Tegmental Area of Human Alcohol Use Disorder Patients: A Postmortem Study

BACKGROUND

The GABAergic neuroactive steroid (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP; allopregnanolone) enhances GABAergic activity and produces subjective effects similar to ethanol (EtOH). The effect of chronic alcohol exposure on 3α,5α-THP concentrations has been studied in mouse, rat, and monkey limbic brain areas. Chronic EtOH exposure produced divergent brain region and cell-specific changes in 3α,5α-THP concentrations in animal studies. However, 3α,5α-THP levels in similar human brain regions have never been examined in individuals diagnosed with alcohol use disorder (AUD). Therefore, we used immunohistochemistry (IHC) to examine 3α,5α-THP levels in the ventral tegmental area (VTA), substantia nigra pars medialis (SNM), and amygdala of human postmortem brains of patients diagnosed with AUD compared with social drinkers. The effects of sex and liver disease on 3α,5α-THP concentrations were examined in the aforementioned brain regions.

METHODS

Human postmortem brains of AUD patients and age-matched controls were obtained from the New South Wales Brain Tissue Resource Center. IHC was performed using anti-3α,5α-THP antibody on formalin-fixed paraffin-embedded brain sections to detect cellular 3α,5α-THP levels. Immunoreactivity was analyzed by pixel density/mm² for the comparison between AUD patients and controls.

RESULTS

3α,5α-THP immunoreactivity was increased by 23.2 ± 9% in the VTA of AUD patients compared with age-matched controls (p = 0.014). Moreover, a 29.6 ± 10% increase in 3α,5α-THP immunoreactivity was observed in the SNM of male AUD patients compared with male controls (p < 0.01), but not in female subjects. 3α,5α-THP immunoreactivity in the VTA and SNM regions did not differ between noncirrhotic and cirrhotic AUD patients. A sex difference in 3α,5α-THP immunoreactivity (female 51 ± 18% greater than male) was observed among control subjects in the SNM, but no other brain region. 3α,5α-THP immunoreactivity in the basolateral amygdala and lateral amygdala was negatively correlated with the length of the tissue fixation time as well as the age of the subjects, precluding assessment of the effect of AUD.

CONCLUSIONS

Cellular 3α,5α-THP levels in VTA are increased in human AUD patients, an effect that is likely independent of sex and liver disease. The differences between animal models and human studies should be factored into the interpretation of the physiological significance of elevated 3α,5α-THP levels in humans.

Clinical Potential of Neurosteroids for CNS Disorders

Neurosteroids are key endogenous molecules in the brain that affect many neural functions. We describe here recent advances in US National Institutes of Health (NIH)-sponsored and other clinical studies of neurosteroids for CNS disorders. The neuronal GABA-A receptor chloride channel is one of the prime molecular targets of neurosteroids. Allopregnanolone-like neurosteroids are potent allosteric agonists as well as direct activators of both synaptic and extrasynaptic GABA-A receptors. Hence, neurosteroids can maximally enhance synaptic phasic and extrasynaptic tonic inhibition. The resulting chloride current conductance generates a form of shunting inhibition that controls network excitability, seizures, and behavior. Such mechanisms of neurosteroids are providing innovative therapies for epilepsy, status epilepticus (SE), traumatic brain injury (TBI), fragile X syndrome (FXS), and chemical neurotoxicity. The neurosteroid field has entered a new era, and many compounds have reached advanced clinical trials. Synthetic analogs have several advantages over natural neurosteroids for clinical use because of their superior bioavailability and safety trends.

Neurosteroidogenesis Today: Novel Targets for Neuroactive Steroid Synthesis and Action and Their Relevance for Translational Research

Neuroactive steroids are endogenous neuromodulators synthesised in the brain that rapidly alter neuronal excitability by binding to membrane receptors, in addition to the regulation of gene expression via intracellular steroid receptors. Neuroactive steroids induce potent anxiolytic, antidepressant, anticonvulsant, sedative, analgesic and amnesic effects, mainly through interaction with the GABAA receptor. They also exert neuroprotective, neurotrophic and antiapoptotic effects in several animal models of neurodegenerative diseases. Neuroactive steroids regulate many physiological functions, such as the stress response, puberty, the ovarian cycle, pregnancy and reward. Their levels are altered in several neuropsychiatric and neurological diseases and both preclinical and clinical studies emphasise a therapeutic potential of neuroactive steroids for these diseases, whereby symptomatology ameliorates upon restoration of neuroactive steroid concentrations. However, direct administration of neuroactive steroids has several challenges, including pharmacokinetics, low bioavailability, addiction potential, safety and tolerability, which limit its therapeutic use. Therefore, modulation of neurosteroidogenesis to restore the altered endogenous neuroactive steroid tone may represent a better therapeutic approach. This review summarises recent approaches that target the neuroactive steroid biosynthetic pathway at different levels aiming to promote neurosteroidogenesis. These include modulation of neurosteroidogenesis through ligands of the translocator protein 18 kDa and the pregnane xenobiotic receptor, as well as targeting of specific neurosteroidogenic enzymes such as 17β-hydroxysteroid dehydrogenase type 10 or P450 side chain cleavage. Enhanced neurosteroidogenesis through these targets may be beneficial not only for neurodegenerative diseases, such as Alzheimer's disease and age-related dementia, but also for neuropsychiatric diseases, including alcohol use disorders.

Variation in AKR1C3, which encodes the neuroactive steroid synthetic enzyme 3α-HSD type 2 (17β-HSD type 5), moderates the subjective effects of alcohol

RATIONALE

Animal models suggest that neuroactive steroids contribute to alcohol's acute effects. We previously reported that a common nonsynonymous polymorphism, AKR1C3 2 in the gene encoding the enzyme 3α-HSD2/17β-HSD5, and a synonymous single nucleotide polymorphism (SNP), rs248793, in SRD5A1, which encodes 5α-reductase, were associated with alcohol dependence (AD).

OBJECTIVES

The aim of the study was to investigate whether these polymorphisms moderate subjective effects of alcohol in humans and whether AKR1C3 2 affects neuroactive steroid synthesis.

METHODS

Sixty-five Caucasian men (34 lighter and 31 heavier drinkers; mean age 26.2 years) participated in a double-blind laboratory study where they consumed drinks containing no ethanol or 0.8 g/kg of ethanol. Breath alcohol, heart rate (HR), and self-reported alcohol effects were measured at 40-min intervals, and genotype was examined as a moderator of alcohol's effects. Levels of the neuroactive steroid 5α-androstane-3α,17β-diol and its precursors, 3α,5α-androsterone and dihydrotestosterone, were measured at study entry using GC/MS.

RESULTS

Initially, carriers of the AD-protective AKR1C3 2 G allele had higher levels of 5α-androstane-3α,17β-diol relative to the precursor 3α,5α-androsterone than C allele homozygotes. AKR1C3 2 G allele carriers exhibited greater increases in heart rate and stimulant and sedative effects of alcohol than C allele homozygotes. The genotype effects on sedation were observed only in heavier drinkers. The only effect of the SRD5A1 SNP was to moderate HR. There were no interactive effects of the two SNPs.

CONCLUSIONS

The observed effects of variation in a gene encoding a neuroactive steroid biosynthetic enzyme on the rate of 17β-reduction of androsterone relative to androstanediol and on alcohol's sedative effects may help to explain the association of AKR1C3 2 with AD.

Divergent neuroactive steroid responses to stress and ethanol in rat and mouse strains: relevance for human studies

RATIONALE

Neuroactive steroids are endogenous or synthetic steroids that rapidly alter neuronal excitability via membrane receptors, primarily γ-aminobutyric acid type A (GABAA) receptors. Neuroactive steroids regulate many physiological processes including hypothalamic-pituitary-adrenal (HPA) axis function, ovarian cycle, pregnancy, aging, and reward. Moreover, alterations in neuroactive steroid synthesis are implicated in several neuropsychiatric disorders.

OBJECTIVES

This review will summarize the pharmacological properties and physiological regulation of neuroactive steroids, with a particular focus on divergent neuroactive steroid responses to stress and ethanol in rats, mice, and humans.

RESULTS

GABAergic neuroactive steroids exert a homeostatic regulation of the HPA axis in rats and humans, whereby the increase in neuroactive steroid levels following acute stress counteracts HPA axis hyperactivity and restores homeostasis. In contrast, in C57BL/6J mice, acute stress decreases neurosteroidogenesis and neuroactive steroids exert paradoxical excitatory effects upon the HPA axis. Rats, mice, and humans also differ in the neuroactive steroid responses to ethanol. Genetic variation in neurosteroidogenesis may explain the different neuroactive steroid responses to stress or ethanol.

CONCLUSIONS

Rats and mouse strains show divergent effects of stress and ethanol on neuroactive steroids in both plasma and brain. The study of genetic variation in the various processes that determine neuroactive steroids levels as well as their effects on cell signaling may underlie these differences and may play a relevant role for the potential therapeutic benefits of neuroactive steroids.