An update on the anxiolytic and neuroprotective properties of etifoxine: from brain GABA modulation to a whole-body mode of action

Intranasal dantrolene nanoparticles inhibit lipopolysaccharide-induced depression and anxiety behavior in mice

This study investigates the therapeutic effectiveness of intranasal dantrolene nanoparticles in the Ryanodex formulation (DNRF) pretreatment to inhibit lipopolysaccharide (LPS)-induced depressive and anxiety behavior in mice. Both wild-type (WT) B6SJLF1/J and 5XFAD adult mice were pretreated with intranasal DNRF (5mg/kg), daily, Monday to Friday, 5 days per week, for 4 weeks. Then, mice were treated with intraperitoneal injection of LPS (5mg/kg) for one time. Behavioral tests for depression and anxiety were performed 24 hours after a one-time LPS injection. Biomarkers for inflammation (IL-1β and IL-18) in blood were measured using enzyme-linked immunosorbent assay (ELISA). In both types of mice, intranasal DNRF significantly inhibited LPS-induced pathological elevation of IL-1β and IL-18 in the blood. Intranasal DNRF abolished LPS-induced depression and anxiety behaviors behavior in both WT and 5XFAD mice, without obvious side effects, which was associated with its significant inhibition of pathological elevation of pyroptosis related cytokines in blood.

Catalyst-Free Synthesis of Functionalized 4-Substituted-4H-Benzo[d][1,3]oxazines via Intramolecular Cyclization of ortho-Amide-N-tosylhydrazones

Functionalized 4-aryl-4H-benzo[d][1,3]oxazines are synthesized under transition-metal-free conditions using ortho-amide-N-tosylhydrazones. This synthetic method uses readily available N-tosylhydrazones as the diazo compound precursors and involves an intramolecular ring closure reaction mediated by a protic polar additive (iPrOH). A wide range of functionalized oxazines are obtained by this straightforward method in good to excellent yields. Furthermore, the viability of our strategy is illustrated by the gram-scale elaboration of a bromo-substituted 4H-benzo[d][1,3]oxazine and its post-functionalization by palladium-catalyzed cross-couplings.

The human microglial surveillant phenotype is preserved by de novo neurosteroidogenesis through the control of cholesterol homeostasis: Crucial role of 18 kDa Translocator Protein

Neurodegenerative disease-associated microglia commonly exhibit harmful cholesterol accumulation that impairs their ability to resolve the neuroinflammatory response, contributing to disease onset and progression. Neurosteroids, whose levels have been often found significantly altered in brain diseases, are the most potent endogenous anti-inflammatory molecules exerting beneficial effects on activities of brain cells, including microglia. For the first time, the impact of neurosteroidogenesis on cholesterol homeostasis for the immune surveillance phenotype maintenance was investigated in a human microglia in vitro model. To enhance and inhibit neurosteroidogenesis, pharmacological stimulation and knock-down of 18 kDa Translocator Protein (TSPO), which is involved in the neurosteroidogenesis rate-limiting step, were used as experimental approaches, respectively. The obtained results point to an essential autocrine control of neurosteroidogenesis in orchestrating cholesterol trafficking in human microglia. TSPO pharmacological stimulation ensured cholesterol turnover by strengthening cholesterol efflux systems and preserving healthy immune surveillant phenotype. Conversely, TSPO knock-down induced an impairment of the controlled interplay among cholesterol synthesis, efflux, and metabolism mechanisms, leading to an excessive cholesterol accumulation and acquisition of a chronically activated dysfunctional phenotype. In this model, the exogenous neurosteroid administration restored proper the cholesterol clearance. The TSPO ability in promoting native neurosteroidogenesis opens the way to restore cholesterol homeostasis, and thus to maintain microglia proper functionality for the treatment of neuroinflammation-related brain diseases.

Anxiolytic-like effects of citral in the mouse elevated plus maze: involvement of GABAergic and serotonergic transmissions

Citral, a monoterpene which is a part of the essential oil of several medicinal plants, is generally regarded as safe for human and animal consumption. Studies have introduced citral as a functional component of some essential oils in anxiolytic and antidepressant therapies; however, the neuropharmacological characteristics of citral have not yet been reported. In the present study, we evaluated the anxiolytic activities of citral in comparison to two standard anxiolytics, diazepam and buspirone, in Swiss albino mice by intraperitoneal administration of 1, 2, 5, 10, and 20 mg/kg using elevated plus maze (EPM) and open-field test (OFT). Moreover, we also examined whether the GABA_A-benzodiazepine and 5-HT_1A receptor are involved in the anxiolytic-like effects of citral by pretreatment with flumazenil and WAY-100635, respectively. Citral dose-dependently decreased the number of border crossings and time spent in borders, and also the number of grooming and rearing in OFT without altering the exploratory behavior of mice. In the EPM, this monoterpene led to a significant increase in number of entries in open arms and time spent in open arms, as well as a decrease in time spent in closed arms. Pretreatment with flumazenil and WAY-100635 both could reverse the anxiolytic effects of the citral in the EPM. These results suggest that anxiolytic activity of citral occurs via the GABA_A and 5-HT_1A receptor modulation.

Palladium-catalyzed synthesis of 4-sila-4H-benzo[d][1,3]oxazines by intramolecular Hiyama coupling

A palladium-catalyzed synthesis of 4-sila-4H-benzo[d][1,3]oxazines, silicon-switched analogs of biologically relevant 4H-benzo[d][1,3]oxazines, was developed by the intramolecular Hiyama coupling of 3-amido-2-(arylsilyl)aryl triflates.

[A role of neurosteroids in the pathogenesis of psychiatric disorders]

Despite the proven importance of neurosteroids in many physiological processes, their role in the pathogenesis of the most of psychiatric disorders remains relatively understudied. This article reviews the current clinical evidence on the effects of neurosteroids on the formation and treatment of anxiety disorder, depression, bipolar disorder, and schizophrenia. In particular, the article points out the ambivalent nature of the effects of neurosteroids on GABA_A- and other receptors. We are especially interested in the anxiolytic and anxiogenic effects of some neurosteroids, the antidepressant effect of allopregnanolone in treating postpartum and other forms of depression, and the nature of short- and long-term mechanisms of antidepressant effects of neurosteroids of different types. The currently unproven hypothesis about the effect of changes in the level of neurosteroids on the course of bipolar disorder is also discussed, with an analysis of the scientific evidence on the development of schizophrenic symptomatology in relation to changing neurosteroid levels in the context of positive and cognitive symptoms.

[Systematic analysis of the results of fundamental and clinical studies of ethifoxin]

The main pharmacological use of etifoxine is the treatment of psychosomatic manifestations of anxiety. The purpose of this work is a systematic analysis of fundamental and clinical studies of etifoxine. In addition to the anxiolytic effect, which partially persists even after discontinuation of therapy, etifoxine is characterized by analgesic, neurotrophic and neuroprotective properties. Such a pharmacological profile of etifoxine is due not only to the activation of GABA receptors, but also to the effect on the levels of neurosteroids in the blood and in the brain. Modulation by etifoxine of neurosteroids' metabolism contributes to the manifestation of anxiolytic, anti-inflammatory, neuroprotective and other properties of etifoxine.

Allosteric modulators of the δ GABAA receptor subtype demonstrate a therapeutic effect in morphine-antinociceptive tolerance and withdrawal in mice

The present study evaluated the effects of compounds targeting extrasynaptic δ subunit-containing γ-aminobutyric acid type A receptors (δ*-GABAARs) to interrogate the role of tonic inhibition in the development of antinociceptive tolerance caused by repeated morphine administration. We investigated the effect of subchronic or acute treatment with non-steroidal positive allosteric modulators (PAMs) of δ*-GABAARs, such as 2-261, on the morphine-antinociceptive tolerance. Mice were treated twice daily with morphine for 9 days and antinociception was measured using the hot water tail immersion test. Co-treatment with 2-261 and morphine prevented morphine-antinociceptive tolerance and acute administration of 2-261 on day 9 was sufficient to reverse the tolerance. Other compounds with activity at δ*-GABAARs also reversed morphine tolerance, whereas an enaminone that lacked activity at δ*-GABAARs did not. Acute administration of 2-261 did not cause an additive or synergistic antinociceptive effect when combined with an acute submaximal dose of morphine. We then used Cre/LoxP recombination to generate GABAA δ-subunit knockout mice to corroborate the pharmacological results. Observations of male δ-knockout mice demonstrated that the δ*-GABAARs was necessary for 2-261 modulation of both analgesic tolerance and somatic withdrawal symptoms produced by subchronic morphine. While female mice still benefited from the positive effects of 2-261, the δ-subunit was not necessary for these effects, highlighting a distinction of the different pathways that could have implications for some of the sex-related differences seen in human opioid-induced outcomes. Consequently, subtype-specific allosteric modulators of GABAARs may warrant further investigation as pharmacological targets to manage tolerance and withdrawal from opioids.

Analysis of the Underlying Mechanism of the Jiu Wei Zhen Xin Formula for Treating Generalized Anxiety Disorder Based on Network Pharmacology of Traditional Chinese Medicine

Currently, there are many effective pharmacological treatments for generalized anxiety disorder (GAD), formulated herbal granule is also an alternative way. Our research intends to construct a pharmacological network on genetic targets and pathways between Jiu Wei Zhen Xin Formula (JWZXF) and GAD. Through the TCMSP database, we collected the active ingredients of JWZXF and potential targets of the active ingredients. The GAD-related proteins collected from GeneCards database and DisGeNET database were combined. Component-target protein networks were constructed and visualized using Cytoscape 3.8.2 software to comprehensively clarify the relationships between ingredients, components, and targets. The intersection targets were imported into the STRING database, and the protein-protein interaction (PPI) network was constructed. We constructed and analyzed the visualized "drug-target-disease" network. Gene Ontology (GO) enrichment together with Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis were conducted on the common target through R language. Forty-one effective components and 106 potential targets of JWZXF were found. There were top ten hub genes and multiple important signaling pathways involved in the treatment of GAD with the JWZXF. This study expounded the pharmacological actions and molecular mechanisms of the JWZXF in treating GAD from a holistic perspective. The potential pharmacological effects of the JWZXF are closely related to regulation because not only does it comprehensively analyze the possible mechanism of JWZXF treatment of GAD but it can also facilitate further in-depth research and provide a theoretical basis for the clinical expansion of its application.

A novel dual mode-of-action anti-hyperalgesic compound in rats which is neuroprotective and promotes neuroregeneration

Chronic neuropathic pain (CNP) can result from surgery or traumatic injury, but also from peripheral neuropathies caused by diseases, viral infections, or toxic treatments. Opioids, although very effective for acute pain, do not prevent the development of CNP, and are considered as insufficient treatment. Therefore, there is high need for effective and safe non-opioid options to treat, prevent and eventually reverse CNP. A more effective approach to alleviating CNP would constitute a treatment that acts concurrently on various mechanisms involved in relieving pain symptoms and preventing or reversing chronification by enhancing both neuroprotection and neuroregeneration. We have identified and characterized GRT-X (N-[(3-fluorophenyl)-methyl]-1-(2-methoxyethyl)-4-methyl-2-oxo-(7-trifluoromethyl)-1H-quinoline-3-caboxylic acid amide), a novel drug which is able to activate both voltage-gated potassium channels of the Kv7 family and the mitochondrial translocator protein 18 kDa (TSPO). The dual mode-of-action (MoA) of GRT-X was indicated in in vitro studies and in vivo in a rat model of diabetic neuropathy. In this model, mechanical hyperalgesia was dose-dependently inhibited. After severe crush lesion of cervical spinal nerves in rats, GRT-X promoted survival, speeded up regrowth of sensory and motor neurons, and accelerated recovery of behavioral and neuronal responses to heat, cold, mechanical and electrical stimuli. These properties may reduce the likelihood of chronification of acute pain, and even potentially relieve established CNP. The absence of a conditioned place preference in rats suggests lack of abuse potential. In conclusion, GRT-X offers a promising preclinical profile with a novel dual MoA.

TSPO: an emerging role in appetite for a therapeutically promising biomarker

There is accumulating evidence that an obesogenic Western diet causes neuroinflammatory damage to the brain, which then promotes further appetitive behaviour. Neuroinflammation has been extensively studied by analysing the translocator protein of 18 kDa (TSPO), a protein that is upregulated in the inflamed brain following a damaging stimulus. As a result, there is a rich supply of TSPO-specific agonists, antagonists and positron emission tomography ligands. One TSPO ligand, etifoxine, is also currently used clinically for the treatment of anxiety with a minimal side-effect profile. Despite the neuroinflammatory pathogenesis of diet-induced obesity, and the translational potential of targeting TSPO, there is sparse literature characterizing the effect of TSPO on appetite. Therefore, in this review, the influence of TSPO on appetite is discussed. Three putative mechanisms for TSPO's appetite-modulatory effect are then characterized: the TSPO–allopregnanolone–GABA_AR signalling axis, glucosensing in tanycytes and association with the synaptic protein RIM-BP1. We highlight that, in addition to its plethora of functions, TSPO is a regulator of appetite. This review ultimately suggests that the appetite-modulating function of TSPO should be further explored due to its potential therapeutic promise.

Presentation and management of anxiety in individuals with acute symptomatic or asymptomatic COVID-19 infection, and in the post-COVID-19 recovery phase

COVID-19 is associated with neuropsychiatric complications, the most frequent one being anxiety. Multiple biological and psychosocial factors contribute to anxiety in COVID-19. Among the biological factors, stress, genetics, gender, immune system, resilience, anosmia, hypogeusia, and central nervous system infection with SARS-CoV-2 are key. Anxiety is a complication of COVID-19 that may exacerbate the infection course, and the infection may exacerbate anxiety. We present the mechanisms of anxiety in symptomatic or asymptomatic COVID-19. We discuss the presentation of anxiety in patients without or with prior psychiatric illness, and with co-morbidities. Timely diagnosis and management of anxiety in COVID-19 patients is important. Given the frequent complication of COVID-19 with Acute Respiratory Distress Syndrome and Intensive Care Unit stay, anxiety may be a long-term complication. We review the diagnostic tools for anxiety in COVID-19, and summarise pharmacologic and non-pharmacologic treatments. We provide recommendations for diagnosis, treatment, prevention and follow up of anxiety in COVID-19.Key pointsPatients with COVID-19 (symptomatic or asymptomatic) exhibit a high frequency of neuropsychiatric complications with highest percentage attributed to anxiety.Multiple biological and psychosocial risk factors for anxiety exist in COVID-19-ill individuals. Biological risk factors include stress, resilience, genetics, gender, age, immune system, direct infection of the central nervous system (CNS) with SARS-CoV-2, comorbid psychiatric and general medical illnesses, ARDS and ICU stay. Anosmia and hypogeusia are COVID-19-specific anxiety risk factors. Knowledge of the anxiety risk factors is essential to focus on timely interventions, because anxiety may be a complication of and exacerbate the COVID-19 course.An inverse correlation exists between resilience and anxiety because of COVID-19, and therefore efforts should be made to increase resilience in COVID-19 patients.In COVID-19, important anxiety mechanism is neuroinflammation resulting from activation of the immune system and an ensuing cytokine storm.The general approach to management of anxiety in COVID-19 should be compassionate, similar to that during trauma or disaster, with efforts focussed on instilling a sense of hope and resilience.In selecting pharmacological treatment of anxiety, the stress response and immune system effects should be key. Medications with cardio-respiratory adverse effects should be avoided in patients with respiratory problems.Anxiety is a disorder that will require for long-term follow up at least one month after COVID-19.

The neuropsychiatric manifestations of COVID-19: Interactions with psychiatric illness and pharmacological treatment

The recent outbreak of the corona virus disease (COVID-19) has had major global impact. The relationship between severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection and psychiatric diseases is of great concern, with an evident link between corona virus infections and various central and peripheral nervous system manifestations. Unmitigated neuro-inflammation has been noted to underlie not only the severe respiratory complications of the disease but is also present in a range of neuro-psychiatric illnesses. Several neurological and psychiatric disorders are characterized by immune-inflammatory states, while treatments for these disorders have distinct anti-inflammatory properties and effects. With inflammation being a common contributing factor in SARS-CoV-2, as well as psychiatric disorders, treatment of either condition may affect disease progression of the other or alter response to pharmacological treatment. In this review, we elucidate how viral infections could affect pre-existing psychiatric conditions and how pharmacological treatments of these conditions may affect overall progress and outcome in the treatment of SARS-CoV-2. We address whether any treatment-induced benefits and potential adverse effects may ultimately affect the overall treatment approach, considering the underlying dysregulated neuro-inflammatory processes and potential drug interactions. Finally, we suggest adjunctive treatment options for SARS-CoV-2-associated neuro-psychiatric symptoms.

Dissociation of endocrine responses to the Trier Social Stress Test in Virtual Reality (VR-TSST) by the benzodiazepine alprazolam and the translocator protein 18 kDa (TSPO) ligand etifoxine

BACKGROUND

Activity of the two major stress systems, the hypothalamic-pituitary-adrenal (HPA) and the sympathetic-adrenal-medullary (SAM) axis, has already been shown to be modulated by different compounds that bind to the central benzodiazepine receptor. Less is known about ligands that modulate the peripheral benzodiazepine receptor - meanwhile known as the translocator protein 18 kDa (TSPO) - which constitute promising candidates in the search of novel anxiolytics. To close this gap, the present study compared the effects of the benzodiazepine alprazolam and the TSPO ligand etifoxine on responses of the HPA and SAM axes to the Trier Social Stress Test, a standardized paradigm to induce acute psychosocial stress in humans, performed in Virtual Reality (VR-TSST).

METHODS

Sixty healthy males, aged between 18 and 55 years, were randomly assigned to receive either a daily dose of 1.5 mg alprazolam, 150 mg etifoxine, or placebo over five days. On the last day of intake, they were exposed to the VR-TSST. We assessed changes of salivary cortisol, allopregnanolone, (nor-) epinephrine in serum, TSPO expression in platelets as well as heart rate (HR), skin conductance level (SCL) and self-reports in response to the stress task. Repeated measures ANOVAs were conducted to examine treatment effects on these stress response variables during the course of VR-TSST.

RESULTS

The response of salivary cortisol to the VR-TSST was significantly blunted in participants pre-treated with alprazolam but was not affected by etifoxine. While levels of allopregnanolone, epinephrine and norepinephrine increased in response to stress, TSPO expression decreased. None of those endocrine stress markers was affected by the active treatments, whereas TSPO expression increased after etifoxine administration over all study days. There were no effects of the two anxiolytics on HR, SCL or any self-report measurement.

CONCLUSION

The current study confirmed the attenuating effects of benzodiazepines on stress-induced HPA axis activity but did not reveal a comparable effect of the TSPO ligand etifoxine. The long-term consequences of a pharmacologically blunted response of the HPA axis to an acute stressor should be further elucidated. Due to the missing effects of etifoxine on stress-related parameters in our sample of healthy subjects, it might be concluded that the therapeutic effects of this TSPO ligand are restricted to stronger or pathological stress responses, respectively.

Etifoxine is non-inferior than clonazepam for reduction of anxiety symptoms in the treatment of anxiety disorders: a randomized, double blind, non-inferiority trial

OBJECTIVE

To determine whether etifoxine, a non-benzodiazepine drug of the benzoxazine family, is non-inferior compared with clonazepam in the treatment of anxiety disorders.

METHOD

A randomized controlled double blind trial with parallel groups was conducted. A total of 179 volunteer patients with a diagnosis of anxiety disorder (DSM-IV), between 18 and 64 years of age, participated in this study. The experimental group received 150 mg/day of etifoxine and the control 1 mg/day of clonazepam, both in three daily doses for 12 weeks. This treatment was completed by 87 participants, and 70 were available for follow-up at 24 weeks from start of treatment. The primary objective was a non-inferiority comparison between etifoxine and clonazepam in the decrease of anxiety symptoms (HAM-A) at 12 weeks of treatment. Secondary outcomes included the evaluation of medication side effects (UKU), anxiety symptoms at 24 weeks of treatment, and clinical improvement (CGI). Data analysis included multiple imputation of missing data. The effect of etifoxine on the HAM-A, UKU, and CGI was evaluated with the intention of treatment, and a sensitivity analysis of the results was conducted. Non-inferiority would be declared by a standardized mean difference (SMD) between clonazepam and etifoxine not superior to 0.31 in favour of clonazepam.

RESULTS

Using imputed data, etifoxine shows non-inferiority to clonazepam on the reduction of anxiety symptoms at the 12-week (SMD = 0.407; 95% CI, 0.069, 0.746) and 24-week follow-ups (SMD = 0.484; 95% CI, 0.163, 0.806) and presented fewer side effects (SMD = 0.58; 95% CI, 0.287, 0.889). LOCF analysis shows that etifoxine is non-inferior to clonazepam on reduction of anxiety symptoms and adverse symptoms even when no change was assigned as result to participant whom withdrew. Non-inferiority could be declared for clinical improvement (SMD = 0.326; 95% CI, - 0.20, 0.858).

CONCLUSION

Etifoxine was non-inferior to clonazepam on reduction of anxiety symptoms, adverse effects, and clinical improvement.

TSPO ligand etifoxine attenuates LPS-induced cognitive dysfunction in mice

The translocator protein (TSPO), once known as peripheral-type benzodiazepine receptor, was reported to be related with several physiological functions. Etifoxine is a clinically available anxiolytic drug, and has recently shown neuroprotective effects as a TSPO ligand. The aim of the present study was to investigate the influence of etifoxine on LPS-induced neuroinflammation and cognitive dysfunction. C57/BL6 male mice were injected with etifoxine (50 mg/kg, i.p.) three days before lipopolysaccharide (LPS, 500 μg/kg, i.p.) administration. Etifoxine pretreatment alleviated hippocampal inflammation, increased brain levels of progesterone, allopregnanolone and attenuated cognitive dysfunction in LPS-injected mice. While LPS increased expression of caspase-3 and decreased p-Akt/Akt, etifoxine returned caspase-3 and p-Akt/Akt to control levels. Finasteride, a 5α-reductase inhibitor that blocked allopregnanolone production, partially reversed the effects of etifoxine. We concluded that etifoxine exerted neuroprotective effects in LPS-induced neuroinflammation and the neuroprotection may be related with increase of neurosteroids synthesis and decrease of apoptosis.

Novel pharmacological targets in drug development for the treatment of anxiety and anxiety-related disorders

Current medication for anxiety disorders is suboptimal in terms of efficiency and tolerability, highlighting the need for improved drug treatments. In this review an overview of drugs being studied in different phases of clinical trials for their potential in the treatment of fear-, anxiety- and trauma-related disorders is presented. One strategy followed in drug development is refining and improving compounds interacting with existing anxiolytic drug targets, such as serotonergic and prototypical GABAergic benzodiazepines. A more innovative approach involves the search for compounds with novel mechanisms of anxiolytic action using the growing knowledge base concerning the relevant neurocircuitries and neurobiological mechanisms underlying pathological fear and anxiety. The target systems evaluated in clinical trials include glutamate, endocannabinoid and neuropeptide systems, as well as ion channels and targets derived from phytochemicals. Examples of promising novel candidates currently in clinical development for generalised anxiety disorder, social anxiety disorder, panic disorder, obsessive compulsive disorder or post-traumatic stress disorder include ketamine, riluzole, xenon with one common pharmacological action of modulation of glutamatergic neurotransmission, as well as the neurosteroid aloradine. Finally, compounds such as D-cycloserine, MDMA, L-DOPA and cannabinoids have shown efficacy in enhancing fear-extinction learning in humans. They are thus investigated in clinical trials as an augmentative strategy for speeding up and enhancing the long-term effectiveness of exposure-based psychotherapy, which could render chronic anxiolytic drug treatment dispensable for many patients. These efforts are indicative of a rekindled interest and renewed optimism in the anxiety drug discovery field, after decades of relative stagnation.