Alcohol dependence and withdrawal increase sensitivity of central amygdalar GABAergic synapses to the glucocorticoid receptor antagonist mifepristone in male rats

Apremilast reduces co-occurring alcohol drinking and mechanical allodynia and regulates central amygdala GABAergic transmission

The FDA-approved phosphodiesterase type 4 (PDE4) inhibitor, apremilast, has been recently investigated as a pharmacotherapy for alcohol use disorder (AUD) with promising efficacy in rodent models and humans. However, apremilast's effects on mechanical allodynia associated with AUD as well as distinct responses of this drug between males and females are understudied. The present study examined the behavioral and electrophysiological effects of apremilast in Marchigian Sardinian alcohol-preferring (msP) rats and their Wistar counterparts. We used a 2-bottle choice (2-BC) alcohol drinking procedure and tested mechanical sensitivity across our drinking regimen. Spontaneous inhibitory GABA-mediated postsynaptic currents from the central nucleus of the amygdala (CeA) following apremilast application were tested in a subset of rats using ex vivo electrophysiology. Transcript levels for Pde4a or -4b subtypes were assessed for their modulation by alcohol. Apremilast reduced alcohol drinking in both strains of rats. Apremilast reduced mechanical allodynia immediately after drinking, persisting into early and late abstinence. Apremilast increased GABAergic transmission in CeA slices of alcohol-exposed Wistars but not msP rats, suggesting neuroadaptations in msPs by excessive drinking and mechanical allodynia. Pde4 subtype transcript levels were increased in CeA by alcohol. These results suggest that apremilast alleviates co-occurring excessive drinking and pain sensitivity, and they further confirm PDE4's role in pain-associated AUD.

Noradrenaline modulates central amygdala GABA transmission and alcohol drinking in female rats

BACKGROUND

Alcohol use disorder (AUD) is a chronic relapsing disorder and a leading preventable cause of death worldwide. The central nucleus of the amygdala (CeA) is a hub for stress and AUD. Noradrenaline (norepinephrine; NE) regulates the brain's response to stress and alcohol. We previously reported that α1 adrenergic receptors drive moderate alcohol intake, while β receptors contribute to excessive drinking associated with dependence in male rats.

METHODS

Here, we determined that alcohol dependence and withdrawal alter the CeA noradrenergic system in female rats using ex vivo electrophysiology, in situ hybridization, site-specific behavioral pharmacology, and RNA-sequencing data from postmortem CeA samples obtained from female donors with and without AUD.

RESULTS

NE bidirectionally (increase and decrease) modulated CeA GABAergic transmission via both α1 and β receptors. Prazosin, an α1 receptor antagonist, reduced moderate alcohol intake in non-dependent female rats and excessive drinking in dependent females, while propranolol, a β receptor antagonist, only reduced excessive drinking in dependent females. While withdrawal produced a partial functional recovery of the NE modulation of the CeA, some of the cellular patterns of adrenergic receptor mRNA expression persist. Although we did not observe any differences in adrenergic receptor gene expression in the CeA from our human AUD donors, we found a downregulation of ADRA1A in the basolateral amygdala and the dorsolateral prefrontal cortex, compared to controls.

CONCLUSIONS

Amygdalar α1 and β adrenergic receptors are key neural substrates of AUD. Our results support ongoing development of receptor-specific medication for AUD and highlight promising efficacy in females.

Modulation of GABAergic system as a therapeutic option in stroke

Stroke is one of the leading causes of death and permanent adult disability worldwide. Despite the improvements in reducing the rate and mortality, the societal burden and costs of treatment associated with stroke management are increasing. Most of the therapeutic approaches directly targeting ischemic injury have failed to reduce short- and long-term morbidity and mortality and more effective therapeutic strategies are still needed to promote post-stroke functional recovery. Decades of stroke research have been focused on hyperexcitability and glutamate-induced excitotoxicity in the acute phase of ischemia and their relation to motor deficits. Recent advances in understanding the pathophysiology of stroke have been made with several lines of evidence suggesting that changes in the neurotransmission of the major inhibitory system via γ-Aminobutyric acid (GABA) play a particularly important role in functional recovery and deserve further attention. The present review provides an overview of how GABAergic neurotransmission changes correlate with stroke recovery and outlines GABAergic system modulators with special emphasis on neurosteroids that have been shown to affect stroke pathogenesis or plasticity or to protect against cognitive decline. Supporting evidence from both animal and human clinical studies is presented and the potential for GABA signaling-targeted therapies for stroke is discussed to translate this concept to human neural repair therapies. Age and sex are considered crucial parameters related to the pathophysiology of stroke and important factors in the development of therapeutic pharmacological strategies. Future work is needed to deepen our knowledge of the neurochemical changes after stroke, extend the conceptual framework, and allow for the development of more effective interventions that include the modulation of the inhibitory system.

Clinical applications of small-molecule GABAAR modulators for neurological disorders

Gamma-aminobutyric acid type A receptor (GABAAR) modulators are crucial in treating neurological and psychiatric disorders, including epilepsy, anxiety, insomnia, and depression. This review examines the synthetic approaches and clinical applications of representative small-molecule GABAAR modulators. Benzodiazepines, such as Diazepam, are well-known positive allosteric modulators (PAMs) that enhance GABAAR function, providing therapeutic effects but also associated with side effects like sedation and dependence. Non-benzodiazepine modulators, including Z-drugs like Zolpidem and Zaleplon, offer improved selectivity for the α1 subunit of GABAAR, reducing some of these side effects. Neurosteroids such as allopregnanolone and its synthetic analogs, including Brexanolone, have emerged as potent GABAAR modulators with applications in conditions like postpartum depression and refractory epilepsy. Advances in molecular biology and pharmacology have facilitated the development of isoform-specific modulators, potentially reducing off-target effects and enhancing therapeutic profiles. Additionally, combining GABAAR modulators with other therapeutic agents has shown promise in enhancing efficacy and minimizing side effects. This review highlights the design strategies, pharmacodynamics, clinical efficacy, and safety profiles of these compounds, emphasizing the opportunities for developing novel GABAAR modulators with improved therapeutic outcomes.

Emerging drugs in phase II and III clinical development for the treatment of alcohol use disorder

INTRODUCTION

Alcohol Use Disorder (AUD) poses an ongoing significant global health burden. AUD is highly prevalent and affects not only the individuals with AUD, but also their communities and society at large. Even though pharmacotherapy is an integral part of AUD treatment, the few available substances show limited efficacy and limited clinical impact. Thus, there is a need for new innovative pharmacotherapeutic approaches.

AREAS COVERED

This paper provides a comprehensive review of drugs approved for the treatment of AUD as well as those currently in phase II and III development. Data from recent clinical trials has been reviewed and supplemented by additional literature based on a systematic search of the PubMed database and clinical trials registries. Compounds discussed include disulfiram, naltrexone, nalmefene, acamprosat, baclofen, sodium oxybate, doxazosin, varenicline, zonisamide, gabapentin, apremilast, ibudilast, ivermectin, tolcapone, mifepristone, suvorexant, ketamine, psilocybin, semaglutide, oxytocin and cannabidiol.

EXPERT OPINION

Even though the majority of the discussed compounds lack sufficient evidence to support their efficacy, multiple promising new treatment options are currently under investigation. Future research has to consider specific phenotypes and subgroups of AUD as well as a possible enhancement of the effects of psychotherapy through combination with pharmacotherapy. Practitioners should be encouraged to use available compounds to support existing therapeutic regimens.

Chemogenetic inhibition of central amygdala CRF-expressing neurons decreases alcohol intake but not trauma-related behaviors in a rat model of post-traumatic stress and alcohol use disorder

Post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD) are often comorbid. Few treatments exist to reduce comorbid PTSD/AUD. Elucidating the mechanisms underlying their comorbidity could reveal new avenues for therapy. Here, we employed a model of comorbid PTSD/AUD, in which rats were subjected to a stressful shock in a familiar context followed by alcohol drinking. We then examined fear overgeneralization and irritability in these rats. Familiar context stress elevated drinking, increased fear overgeneralization, increased alcohol-related aggressive signs, and elevated peripheral stress hormones. We then examined transcripts of stress- and fear-relevant genes in the central amygdala (CeA), a locus that regulates stress-mediated alcohol drinking. Compared with unstressed rats, stressed rats exhibited increases in CeA transcripts for Crh and Fkbp5 and decreases in transcripts for Bdnf and Il18. Levels of Nr3c1 mRNA, which encodes the glucocorticoid receptor, increased in stressed males but decreased in stressed females. Transcripts of Il18 binding protein (Il18bp), Glp-1r, and genes associated with calcitonin gene-related peptide signaling (Calca, Ramp1, Crlr-1, and Iapp) were unaltered. Crh, but not Crhr1, mRNA was increased by stress; thus, we tested whether inhibiting CeA neurons that express corticotropin-releasing factor (CRF) suppress PTSD/AUD-like behaviors. We used Crh-Cre rats that had received a Cre-dependent vector encoding hM4D(Gi), an inhibitory Designer Receptors Exclusively Activated by Designer Drugs. Chemogenetic inhibition of CeA CRF neurons reduced alcohol intake but not fear overgeneralization or irritability-like behaviors. Our findings suggest that CeA CRF modulates PTSD/AUD comorbidity, and inhibiting CRF neural activity is primarily associated with reducing alcohol drinking but not trauma-related behaviors that are associated with PTSD/AUD.

IL-18 Signaling in the Rat Central Amygdala Is Disrupted in a Comorbid Model of Post-Traumatic Stress and Alcohol Use Disorder

Alcohol use disorder (AUD) and anxiety disorders are frequently comorbid and share dysregulated neuroimmune-related pathways. Here, we used our established rat model of comorbid post-traumatic stress disorder (PTSD)/AUD to characterize the interleukin 18 (IL-18) system in the central amygdala (CeA). Male and female rats underwent novel (NOV) and familiar (FAM) shock stress, or no stress (unstressed controls; CTL) followed by voluntary alcohol drinking and PTSD-related behaviors, then all received renewed alcohol access prior to the experiments. In situ hybridization revealed that the number of CeA positive cells for Il18 mRNA increased, while for Il18bp decreased in both male and female FAM stressed rats versus CTL. No changes were observed in Il18r1 expression across groups. Ex vivo electrophysiology showed that IL-18 reduced GABAA-mediated miniature inhibitory postsynaptic currents (mIPSCs) frequencies in CTL, suggesting reduced CeA GABA release, regardless of sex. Notably, this presynaptic effect of IL-18 was lost in both NOV and FAM males, while it persisted in NOV and FAM females. IL-18 decreased mIPSC amplitude in CTL female rats, suggesting postsynaptic effects. Overall, our results suggest that stress in rats with alcohol access impacts CeA IL-18-system expression and, in sex-related fashion, IL-18's modulatory function at GABA synapses.

Theoretical Frameworks and Mechanistic Aspects of Alcohol Addiction: Alcohol Addiction as a Reward Deficit/Stress Surfeit Disorder

Alcohol use disorder (AUD) can be defined by a compulsion to seek and take alcohol, the loss of control in limiting intake, and the emergence of a negative emotional state when access to alcohol is prevented. Alcohol use disorder impacts multiple motivational mechanisms and can be conceptualized as a disorder that includes a progression from impulsivity (positive reinforcement) to compulsivity (negative reinforcement). Compulsive drug seeking that is associated with AUD can be derived from multiple neuroadaptations, but the thesis argued herein is that a key component involves the construct of negative reinforcement. Negative reinforcement is defined as drug taking that alleviates a negative emotional state. The negative emotional state that drives such negative reinforcement is hypothesized to derive from the dysregulation of specific neurochemical elements that are involved in reward and stress within basal forebrain structures that involve the ventral striatum and extended amygdala, respectively. Specific neurochemical elements in these structures include decreases in reward neurotransmission (e.g., decreases in dopamine and opioid peptide function in the ventral striatum) and the recruitment of brain stress systems (e.g., corticotropin-releasing factor [CRF]) in the extended amygdala, which contributes to hyperkatifeia and greater alcohol intake that is associated with dependence. Glucocorticoids and mineralocorticoids may play a role in sensitizing the extended amygdala CRF system. Other components of brain stress systems in the extended amygdala that may contribute to the negative motivational state of withdrawal include norepinephrine in the bed nucleus of the stria terminalis, dynorphin in the nucleus accumbens, hypocretin and vasopressin in the central nucleus of the amygdala, and neuroimmune modulation. Decreases in the activity of neuropeptide Y, nociception, endocannabinoids, and oxytocin in the extended amygdala may also contribute to hyperkatifeia that is associated with alcohol withdrawal. Such dysregulation of emotional processing may also significantly contribute to pain that is associated with alcohol withdrawal and negative urgency (i.e., impulsivity that is associated with hyperkatifeia during hyperkatifeia). Thus, an overactive brain stress response system is hypothesized to be activated by acute excessive drug intake, to be sensitized during repeated withdrawal, to persist into protracted abstinence, and to contribute to the compulsivity of AUD. The combination of the loss of reward function and recruitment of brain stress systems provides a powerful neurochemical basis for a negative emotional state that is responsible for the negative reinforcement that at least partially drives the compulsivity of AUD.

Glucocorticoid receptors regulate central amygdala GABAergic synapses in Marchigian-Sardinian alcohol-preferring rats

Impairments in the function of the hypothalamic-pituitary-adrenal (HPA) axis and enhanced glucocorticoid receptor (GR) activity in the central amygdala (CeA) are critical mechanisms in the pathogenesis of alcohol use disorder (AUD). The GR antagonist mifepristone attenuates craving in AUD patients, alcohol consumption in AUD models, and decreases CeA γ-aminobutyric acid (GABA) transmission in alcohol-dependent rats. Previous studies suggest elevated GR activity in the CeA of male alcohol-preferring Marchigian-Sardinian (msP) rats, but its contribution to heightened CeA GABA transmission driving their characteristic post-dependent phenotype is largely unknown. We determined Nr3c1 (the gene encoding GR) gene transcription in the CeA in male and female msP and Wistar rats using in situ hybridization and studied acute effects of mifepristone (10 μM) and its interaction with ethanol (44 mM) on pharmacologically isolated spontaneous inhibitory postsynaptic currents (sIPSCs) and electrically evoked inhibitory postsynaptic potentials (eIPSPs) in the CeA using ex vivo slice electrophysiology. Female rats of both genotypes expressed more CeA GRs than males, suggesting a sexually dimorphic GR regulation of CeA activity. Mifepristone reduced sIPSC frequencies (GABA release) and eIPSP amplitudes in msP rats of both sexes, but not in their Wistar counterparts; however, it did not prevent acute ethanol-induced increase in CeA GABA transmission in male rats. In msP rats, GR regulates CeA GABAergic signaling under basal conditions, indicative of intrinsically active GR. Thus, enhanced GR function in the CeA represents a key mechanism contributing to maladaptive behaviors associated with AUD.

FKBP5 inhibitors modulate alcohol drinking and trauma-related behaviors in a model of comorbid post-traumatic stress and alcohol use disorder

Post-traumatic stress disorder (PTSD) leads to enhanced alcohol drinking and development of alcohol use disorder (AUD). Identifying shared neural mechanisms might help discover new therapies for PTSD/AUD. Here, we employed a rat model of comorbid PTSD/AUD to evaluate compounds that inhibit FK506-binding protein 51 (FKBP5), a co-chaperone modulator of glucocorticoid receptors implicated in stress-related disorders. Male and female rats received a familiar avoidance-based shock stress followed by voluntary alcohol drinking. We then assessed trauma-related behaviors through sleep bout cycles, hyperarousal, fear overgeneralization, and irritability. To evaluate the role of stress and alcohol history on the sensitivity to FKBP5 inhibitors, in two separate studies, we administered two FKBP5 inhibitors, benztropine (Study 1) or SAFit2 (Study 2). FKBP5 inhibitors were administered on the last alcohol drinking session and prior to each trauma-related behavioral assessment. We also measured plasma corticosterone to assess the actions of FKBP5 inhibitors after familiar shock stress and alcohol drinking. Benztropine reduced alcohol preference in stressed males and females, while aggressive bouts were reduced in benztropine-treated stressed females. During hyperarousal, benztropine reduced several startle response outcomes across stressed males and females. Corticosterone was reduced in benztropine-treated stressed males. The selective FKBP5 inhibitor, SAFit2, reduced alcohol drinking in stressed males but not females, with no differences in irritability. Importantly, SAFit2 decreased fear overgeneralization in stressed males and females. SAFit2 also reduced corticosterone across stressed males and females. Neither FKBP5 inhibitor changed sleep bout structure. These findings indicate that FKBP5 inhibitors modulate stress-related alcohol drinking and partially modulate trauma-related behaviors. This work supports the hypothesis that targeting FKBP5 may alleviate PTSD/AUD comorbidity.

The glucagon-like peptide-1 (GLP-1) analogue semaglutide reduces alcohol drinking and modulates central GABA neurotransmission

Growing evidence indicates that the glucagon-like peptide-1 (GLP-1) system is involved in the neurobiology of addictive behaviors, and GLP-1 analogues may be used for the treatment of alcohol use disorder (AUD). Here, we examined the effects of semaglutide, a long-acting GLP-1 analogue, on biobehavioral correlates of alcohol use in rodents. A drinking-in-the-dark procedure was used to test the effects of semaglutide on binge-like drinking in male and female mice. We also tested the effects of semaglutide on binge-like and dependence-induced alcohol drinking in male and female rats, as well as acute effects of semaglutide on spontaneous inhibitory postsynaptic currents (sIPSCs) from central amygdala (CeA) and infralimbic cortex (ILC) neurons. Semaglutide dose-dependently reduced binge-like alcohol drinking in mice; a similar effect was observed on the intake of other caloric/noncaloric solutions. Semaglutide also reduced binge-like and dependence-induced alcohol drinking in rats. Semaglutide increased sIPSC frequency in CeA and ILC neurons from alcohol-naive rats, suggesting enhanced GABA release, but had no overall effect on GABA transmission in alcohol-dependent rats. In conclusion, the GLP-1 analogue semaglutide decreased alcohol intake across different drinking models and species and modulated central GABA neurotransmission, providing support for clinical testing of semaglutide as a potentially novel pharmacotherapy for AUD.

The effect of chronic alcohol exposure on spatial memory and BDNF-TrkB- PLCγ1 signaling in the hippocampus of male and female mice

Alcohol is a commonly used drug worldwide, and abuse of alcohol has become a serious public health problem. Alcohol consumption over time can cause cognitive deficits and memory impairment, which is thought to be associated with changes in the hippocampus. Given previously known effects of brain-derived neurotrophic factor (BDNF) in regulating synaptic plasticity and learning and memory, we investigated the effect of chronic alcohol consumption on spatial memory impairment in both sexes and changes in BDNF signaling in the hippocampus. After 4 weeks of intermittent access to 20% alcohol, memory impairment in both male and female mice was evaluated using the Morris water maze and the expression of BDNF, TrkB, phosphorylation of PLCγ1 (p-PLCγ1) and PLCγ1 in the hippocampus was examined using Western blot. As expected, females spent longer escape latencies during the training phase, and both sexes spent shorter time in the target quadrant. Furthermore, after 4 weeks 20% alcohol exposure, we found significantly decreased expression levels of BDNF in the hippocampus of female mice but increased levels in male mice. TrkB and PLCγ1 expression showed no significant change in the hippocampus of both sexes. These findings suggest that chronic alcohol exposure may induce spatial memory impairment in both sexes and opposite changes in expression of BDNF and p-PLCγ1 in the hippocampus of males and females.

Update on the Role of Glucocorticoid Signaling in Osteoblasts and Bone Marrow Adipocytes During Aging

PURPOSE OF REVIEW

Bone marrow adipose tissue (BMAT) in the skeleton likely plays a variety of physiological and pathophysiological roles that are not yet fully understood. In elucidating the complex relationship between bone and BMAT, glucocorticoids (GCs) are positioned to play a key role, as they have been implicated in the differentiation of bone marrow mesenchymal stem cells (BMSCs) between osteogenic and adipogenic lineages. The purpose of this review is to illuminate aspects of both endogenous and exogenous GC signaling, including the influence of GC receptors, in mechanisms of bone aging including relationships to BMAT.

RECENT FINDINGS

Harmful effects of GCs on bone mass involve several cellular pathways and events that can include BMSC differentiation bias toward adipogenesis and the influence of mature BMAT on bone remodeling through crosstalk. Interestingly, BMAT involvement remains poorly explored in GC-induced osteoporosis and warrants further investigation. This review provides an update on the current understanding of the role of glucocorticoids in the biology of osteoblasts and bone marrow adipocytes (BMAds).

Clinical Utility of Mifepristone: Apprising the Expanding Horizons

Mifepristone is a progesterone and glucocorticoid receptor antagonist. Medical abortion with mifepristone and prostaglandin has revolutionized the abortion process extending abortion care to the doors of females. From as low as 2 mg/day to doses extending to 600 mg, from daily dosing to single dosage treatment, mifepristone has a wide perspective in the treatment of various pathologies. Cervical dilatation and myometrial contractility have made the utility of mifepristone feasible for second-trimester termination of pregnancy and induction of labor awaiting Food and Drug Administration approvals. Its anti-progesterone action on the menstrual cycle has a new dimension of use as a contraceptive, as well as use as a menstruation inductive agent. Its role in endometriosis, ectopic pregnancy, and adenomyosis requires more intensive research. Apoptotic action of mifepristone, interference of heterotypic cell adhesion to the basement membrane, cell migration, growth inhibition of various cancer cell lines, decreased epidermal growth factor expression, suppression of invasive and metastatic cancer potential, increase in tumor necrosis factor, downregulation of cyclin-dependent kinase 2, B-cell lymphoma 2, and Nuclear factor kappa B have opened its potential to be explored as anti-cancer treatment and its effects on leiomyoma. The drug needs to be studied more for the prospectus of its anti-glucocorticoid actions in a wider dimension beyond its acquiescence for the treatment of Cushing syndrome.

Alcohol Dependence Induces CRF Sensitivity in Female Central Amygdala GABA Synapses

Alcohol use disorder (AUD) is a chronically relapsing disease characterized by loss of control in seeking and consuming alcohol (ethanol) driven by the recruitment of brain stress systems. However, AUD differs among the sexes: men are more likely to develop AUD, but women progress from casual to binge drinking and heavy alcohol use more quickly. The central amygdala (CeA) is a hub of stress and anxiety, with corticotropin-releasing factor (CRF)-CRF1 receptor and Gamma-Aminobutyric Acid (GABA)-ergic signaling dysregulation occurring in alcohol-dependent male rodents. However, we recently showed that GABAergic synapses in female rats are less sensitive to the acute effects of ethanol. Here, we used patch-clamp electrophysiology to examine the effects of alcohol dependence on the CRF modulation of rat CeA GABAergic transmission of both sexes. We found that GABAergic synapses of naïve female rats were unresponsive to CRF application compared to males, although alcohol dependence induced a similar CRF responsivity in both sexes. In situ hybridization revealed that females had fewer CeA neurons containing mRNA for the CRF1 receptor (Crhr1) than males, but in dependence, the percentage of Crhr1-expressing neurons in females increased, unlike in males. Overall, our data provide evidence for sexually dimorphic CeA CRF system effects on GABAergic synapses in dependence.