Xenon in the treatment of panic disorder: an open label study

Xenon gas as a potential treatment for opioid use disorder, alcohol use disorder, and related disorders

Xenon gas is considered to be a safe anesthetic and imaging agent. Research on its other potentially beneficial effects suggests that xenon may have broad efficacy for treating health disorders. A number of reviews on xenon applications have been published, but none have focused on substance use disorders. Accordingly, we review xenon effects and targets relevant to the treatment of substance use disorders, with a focus on opioid use disorder and alcohol use disorder. We report that xenon inhaled at subsedative concentrations inhibits conditioned memory reconsolidation and opioid withdrawal symptoms. We review work by others reporting on the antidepressant, anxiolytic, and analgesic properties of xenon, which could diminish negative affective states and pain. We discuss research supporting the possibility that xenon could prevent analgesic- or stress-induced opioid tolerance and, by so doing could reduce the risk of developing opioid use disorder. The rapid kinetics, favorable safety and side effect profiles, and multitargeting capability of xenon suggest that it could be used as an ambulatory on-demand treatment to rapidly attenuate maladaptive memory, physical and affective withdrawal symptoms, and pain drivers of substance use disorders when they occur. Xenon may also have human immunodeficiency virus and oncology applications because its effects relevant to substance use disorders could be exploited to target human immunodeficiency virus reservoirs, human immunodeficiency virus protein-induced abnormalities, and cancers. Although xenon is expensive, low concentrations exert beneficial effects, and gas separation, recovery, and recycling advancements will lower xenon costs, increasing the economic feasibility of its therapeutic use. More research is needed to better understand the remarkable repertoire of effects of xenon and its potential therapeutic applications.

Inhaled xenon modulates microglia and ameliorates disease in mouse models of amyloidosis and tauopathy

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder. Antiamyloid antibody treatments modestly slow disease progression in mild dementia due to AD. Emerging evidence shows that homeostatic dysregulation of the brain immune system, especially that orchestrated by microglia, plays an important role in disease onset and progression. Thus, a major question is how to modulate the phenotype and function of microglia to treat AD. Xenon (Xe) gas is a noble gas used in human patients as an anesthetic and a neuroprotectant used for treating brain injuries. Xe penetrates the blood-brain barrier, which could make it an effective therapeutic. To assess the effect of Xe on microglia and AD pathology, we designed a custom Xe inhalation chamber and treated several mouse models of AD with Xe gas. Xe treatment induced mouse microglia to adopt an intermediate activation state that we have termed pre-neurodegenerative microglia (pre-MGnD). This microglial phenotypic transition was observed in mouse models of acute neurodegeneration and amyloidosis (APP/PS1 and 5xFAD mice) and tauopathy (P301S mice). This microglial state enhanced amyloid plaque compaction and reduced dystrophic neurites in the APP/PS1 and 5xFAD mouse models. Moreover, Xe inhalation reduced brain atrophy and neuroinflammation and improved nest-building behavior in P301S mice. Mechanistically, Xe inhalation induced homeostatic brain microglia toward a pre-MGnD state through IFN-γ signaling that maintained the microglial phagocytic response in APP/PS1 and 5xFAD mice while suppressing the microglial proinflammatory phenotype in P301S mice. These results support the translation of Xe inhalation as an approach for treating AD.

Neural Network Excitation/Inhibition: A Key to Empathy and Empathy Impairment

Empathy is an ability to fully understand and feel the mental states of others. We emphasize that empathy is elicited by the transmission of pain, fear, and sensory information. In clinical studies, impaired empathy has been observed in most psychiatric conditions. However, the precise impairment mechanism of the network systems on the pathogenesis of empathy impairment in psychiatric disorders is still unclear. Multiple lines of evidence suggest that disturbances in the excitatory/inhibitory balance in neurologic disorders are key to empathetic impairment in psychiatric disorders. Therefore, we here describe the roles played by the anterior cingulate cortex- and medial prefrontal cortex-dependent neural circuits and their impairments in psychiatric disorders, including anxiety, depression, and autism. In addition, we review recent studies on the role of microglia in neural network excitation/inhibition imbalance, which contributes to a better understanding of the neural network excitation/inhibition imbalance and may open up innovative psychiatric therapies.

Alleviating anxiety and taming trauma: Novel pharmacotherapeutics for anxiety disorders and posttraumatic stress disorder

Psychiatric disorders associated with psychological trauma, stress and anxiety are a highly prevalent and increasing cause of morbidity worldwide. Current therapeutic approaches, including medication, are effective in alleviating symptoms of anxiety disorders and posttraumatic stress disorder (PTSD), at least in some individuals, but have unwanted side-effects and do not resolve underlying pathophysiology. After a period of stagnation, there is renewed enthusiasm from public, academic and commercial parties in designing and developing drug treatments for these disorders. Here, we aim to provide a snapshot of the current state of this field that is written for neuropharmacologists, but also practicing clinicians and the interested lay-reader. After introducing currently available drug treatments, we summarize recent/ongoing clinical assessment of novel medicines for anxiety and PTSD, grouped according to primary neurochemical targets and their potential to produce acute and/or enduring therapeutic effects. The evaluation of putative treatments targeting monoamine (including psychedelics), GABA, glutamate, cannabinoid, cholinergic and neuropeptide systems, amongst others, are discussed. We emphasize the importance of designing and clinically assessing new medications based on a firm understanding of the underlying neurobiology stemming from the rapid advances being made in neuroscience. This includes harnessing neuroplasticity to bring about lasting beneficial changes in the brain rather than - as many current medications do - produce a transient attenuation of symptoms, as exemplified by combining psychotropic/cognitive enhancing drugs with psychotherapeutic approaches. We conclude by noting some of the other emerging trends in this promising new phase of drug development.

Repetitive xenon treatment improves post-stroke sensorimotor and neuropsychiatric dysfunction

Stroke is a life-changing event as stroke survivors experience changes in personality, emotions and mood. We investigated the effect of xenon gas encapsulated in liposomes on stroke-generated sensorimotor impairments, and anxiety- and depression-like phenotypes. Ischemic stroke was created by the intraluminal middle cerebral artery occlusion (MCAO) for 6 h followed by reperfusion in rats. Xenon-liposome (6 mg/kg, intravenous) treatment was given multiple times starting at 2 h post-ischemia through 6 h (5X), and once-daily for next 3 days. Rats underwent ischemic injury displayed sensorimotor deficits in the adhesive removal, vibrissae-evoked forelimb placement and rotarod tests. These animals also made lesser entries and spent less time on open arms of the elevated-plus maze and swam more in passive mode in the forced swimming test, indicating anxiety- and depression-like behaviors at 28- and 35-days post-injury, respectively. Repeated intravenous treatment with xenon-liposomes ameliorated these behavioral aberrations (p < 0.05). Gut microbiome analysis (16S ribosomal-RNA gene sequencing) showed a decrease in the Clostridium clusters XI, XIVa, XVIII and Lactobacillus bacterium, and increase of the Prevotella in the xenon-liposome group. No microbiota communities were majorly affected across the treatments. Moreover, xenon treatment group showed augmented plasma levels of IL-6 cytokines (∼5 fold) on day-35 post-ischemia, while no change was noticed in the IL-1β, IL-4, IL-10, IL-13 and MCP-1 levels. Our data highlights the safety, behavioral recovery and reversal of post-stroke brain injury following xenon-liposome treatment in an extended ischemic model. These results show the potential for this treatment strategy to be translated to patients with stroke.

A case of xenon inhalation therapy for respiratory failure and neuropsychiatric disorders associated with COVID-19

Acute respiratory distress syndrome (ARDS) is the main danger to the life of patients with pneumonia caused by SARS-CoV-2. At the same time, respiratory failure (RF) after ARDS can persist for a long time despite intensive therapy. Therefore, it is important to develop new effective approaches for restoring the ventilation function of the lungs after COVID-19. Here, we present a case report of effective application of short-term inhalations of xenon-oxygen (Xe/O₂) gas mixture for treatment of RF and neuropsychiatric disorders (NPD) associated with COVID-19. The patient inhaled a gas mixture of 70 % Xe and 30 % O₂. We used multispiral computed tomography, evaluated psychometry, studied hematological and biochemical blood parameters, and applied some other methods of clinical studies to assess the therapeutic effectiveness of Xe inhalation. Also, we studied the mechanism of action of xenon with computer modeling. The clinical case showed the high efficacy of Xe/O₂ mixture for treating severe RF and NPD after SARS-CoV-2 infection. Xenon inhalations dramatically increased oxygen saturation and the degree of pneumatization of the lungs. We found out that in coronavirus pneumonia, saturated phospholipids of surfactant are transferred to the solid-ordered phase, which disrupts the surface tension of the alveoli and alveolar gas exchange. Using molecular modeling methods, we demonstrated that the xenon atom increases the distance between the acyl chains of phospholipids due to the van der Waals dispersion interaction. These changes allow for the phase transition of phospholipids from the solid-ordered phase to the liquid phase and restore the functional activity of the surfactant. The findings suggest the feasibility of conducting studies on the effectiveness of Xe/O₂ inhalations for treating ARDS in SARS-CoV-2 infection.

Homeostatic and endocrine responses as the basis for systemic therapy with medical gases: ozone, xenon and molecular hydrogen

Among medical gases, including gases used therapeutically, this review discusses the comparative physiological activity of three gases - ozone (O3), xenon (Xe) and molecular hydrogen (H2), which together form representatives of three types of substances - typical oxidizing, inert, and typical reducing agents. Upon analysis of published and proprietary data, we concluded that these three medical gases can manipulate the neuroendocrine system, by modulating the production or release of hormones via the hypothalamic-pituitary-adrenal, hypothalamic-pituitary-thyroid, hypothalamic-pituitary-gonadal axes, or the gastrointestinal pathway. With repeated administration of the gases over time, these modulations become a predictable consequence of conditioned homeostatic reflexes, resulting in regulation of physiological activity. For example, the regular activation of the unconditioned defense reflex in response to repeated intoxication by ozone leads to the formation of an anticipatory stable conditioned response, which counteracts the toxic action of O3. The concept of a Pavlovian conditioned reflex (or hormoligosis) is a brief metaphor for the understanding the therapeutic effect of systemic ozone therapy.

Experimental Drugs for Panic Disorder: An Updated Systematic Review

Several effective pharmacological therapies for panic disorder (PD) are available, but they have some drawbacks, and unsatisfactory outcomes can occur. Expanding the variety of anti-panic medications may allow for improving PD treatment. The authors performed an updated systematic review of preclinical and clinical (Phase I–III) pharmacological studies to look for advances made in the last six years concerning novel-mechanism-based anti-panic compounds or using medications approved for nonpsychiatric medical conditions to treat PD. The study included seven published articles presenting a series of preclinical studies, two Phase I clinical studies with orexin receptor (OXR) antagonists, and two clinical studies investigating the effects of D-cycloserine (DCS) and xenon gas in individuals with PD. The latest preclinical findings confirmed and expanded previous promising indications of OXR1 antagonists as novel-mechanism-based anti-panic compounds. Translating preclinical research into clinical applications remains in the early stages. However, limited clinical findings suggested the selective OXR1 antagonist JNJ-61393115 may exert anti-panic effects in humans. Overall, OXR1 antagonists displayed a favorable profile of short-term safety and tolerability. Very preliminary suggestions of possible anti-panic effects of xenon gas emerged but need confirmation with more rigorous methodology. DCS did not seem promising as an enhancer of cognitive-behavioral therapy in PD. Future studies, including objective panic-related physiological parameters, such as respiratory measures, and expanding the use of panic vulnerability biomarkers, such as hypersensitivity to CO₂ panic provocation, may allow for more reliable conclusions about the anti-panic properties of new compounds.

Combination therapy with neuropeptides for the treatment of anxiety disorder

Anxiety is a neurological disorder that is characterized by excessive, persistent, and unreasonable worry about everyday things like family, work, money, and relationships. The current therapy used for the treatment has many disadvantages like higher cost, severe adverse reactions, and has suboptimal efficiency. There is a need to look for more innovative approaches for the treatment of anxiety disorder which overcomes the disadvantages of conventional treatment. Recent findings suggest a strong correlation of glutamate with anxiety. Some promising drugs which have a novel mechanism for anxiolytic action are currently under clinical development for generalized anxiety disorder, social anxiety disorder, panic disorder, obsessive-compulsive disorder, or post-traumatic stress disorder. Similarly, an interrelation of oxytocin with neuropeptide S or glutamate or vasopressin can also be considered for further evaluation for the development of new drugs for anxiety treatment. Anxiolytic drug development is a multi-target approach, with the idea of more efficiently equilibrating perturbed circuits. This review focuses on targeting unconventional targets like the glutamate system, voltage-gated ion channels, and neuropeptides system either alone or in combination for the treatment of anxiety disorder.

Xenon produces rapid antidepressant- and anxiolytic-like effects in lipopolysaccharide-induced depression mice model

Onset delay of current antidepressants is always the most significant limitation for the treatment of depression. More attention has been given to the glutamate acid system for developing fast-onset antidepressants. Xenon, acting as a well-known N-methyl-D-aspartate receptors antagonist, has been widely used clinically as anesthetics and was reported to exert antidepressant-like effects in rats under normal condition. The robust and rapid-acting antidepressant- and anxiolytic-like activities of xenon through the use of depression rodent model are still elusive. By using lipopolysaccharide-induced depression mice models, the present study aimed to evaluate the fast-acting antidepressant-like effects of xenon pretreatment. Behavioral tests, mainly including open-field test, novelty-suppressed feeding test, sucrose preference test, tail suspension test, and forced swimming test, were conducted respectively. Our results showed that both xenon gas and xenon-rich saline pretreatment intraperitoneally produced significant antidepressant- and anxiolytic-like activities in mice under normal condition. Further, xenon gas pretreatment (intraperitoneally) rapidly blocked lipopolysaccharide-induced depression- and anxiety-like behaviors of mice. These findings provide direct evidence that xenon could produce fast-onset antidepressant- and anxiolytic-like activities, which highlights the possibility to develop xenon as a promising fast-acting drug for treatment of depression, anxiety, and even other stress-related diseases.

Beneficial effects of xenon inhalation on behavioral changes in a valproic acid-induced model of autism in rats

BACKGROUND

Xenon (Xe) is a noble gas that has been used for the last several decades as an anesthetic during surgery. Its antagonistic effect on glutamate subtype of NMDA (N-methyl-D-aspartate) receptors resulted in evaluation of this gas for treatment of CNS pathologies, including psychoemotional disorders. The aim of this study was to assess the behavioral effects of acute inhalation of subanesthetic concentrations of Xe and to study the outcomes of Xe exposure in valproic acid (VPA)-induced rodent model of autism.

METHODS

We have conducted two series of experiments with a battery of behavioral tests aimed to evaluate locomotion, anxiety- and depression-like behavior, and social behavior in healthy, VPA-treated and Xe-exposed young rats.

RESULTS

We have shown that in healthy animals Xe exposure resulted in acute and delayed decrease of exploratory motivation, partial decrease in risk-taking and depressive-like behavior as well as improved sensorimotor integration during the negative geotaxis test. Acute inhalations of Xe in VPA-exposed animals led to improvement in social behavior, decrease in exploratory motivation, and normalization of behavior in forced-swim test.

CONCLUSION

Behavioral modulatory effects of Xe are probably related to its generalized action on excitatory/inhibitory balance within the CNS. Our data suggest that subanesthetic short-term exposures to Xe have beneficial effect on several behavioral modalities and deserves further investigation.

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.

Prospects for Applying Xenon Curative Properties in Pediatrics

The review discusses experimental and clinical trials on applying noble gas Xenon to treat therapeutic conditions in adults, as well as the prospects for its applying in children. Xenon therapeutic effects on the body are based on the healing properties of a noble gas. Xenon is close to the ‘ideal anesthetic’ by its anesthetic properties; but in addition, it possesses organoand neuroprotective as well as anti-stress properties which have been proved in experiment and clinically. Xenon in pediatric practice is an attractive agent because it is non-toxic, effective for the treatment of posthypoxic and traumatic impairments of the central nervous system, pain syndromes and stress conditions at its therapeutic concentration up to 30%.

Intravenous infusion of xenon-containing liposomes generates rapid antidepressant-like effects

AIM

Similar to ketamine, xenon gas acts as a glutamatergic N-methyl-d-aspartate receptor antagonist, but devoid of propensity to cause untoward effects. Herein, we loaded xenon gas into a liposomal carrier called xenon-containing liposomes (Xe-liposome) for systemic delivery, and investigated its effect as an antidepressant and also analyzed synaptic biomarkers including brain-derived neurotrophic factor (BDNF), protein kinase B (AKT), mammalian target of rapamycin (mTOR), protein kinase C (PKC) and extracellular signal-regulated kinase-1/2 (ERK1/2) in blood and brain.

METHODS

Xe-liposomes (15 μl/mg) were prepared by a pressurized freeze-thaw method, and injected via the lateral tail vein (0.6 mL/rat) in male Wistar rats. The uncaging of xenon gas from circulating Xe-liposome was facilitated by continuous ultrasound application externally on the neck over the internal common carotid artery. One-hour after Xe-liposome infusion, animals were assessed for depression-like behaviors using a forced swimming test (FST), and spontaneous locomotor activity. Blood, as well as frontal cortex and hippocampal samples were obtained for immunoblotting and/or enzyme-linked immune sorbent assays.

RESULTS

Acute intravenous infusion of Xe-liposome, at 6 mg/kg, showed an increase in swimming time in the FST (p < 0.006), indicating antidepressant-like phenotypes. Higher doses of Xe-liposomes (9 mg/kg) failed to improve swimming duration. This behavioral discrepancy was not associated with locomotion aberrations, as gross activity of rats remained similar for both doses. In biochemical analyses of frontal cortex, protein levels of BDNF increased by 64%, and enhanced phosphorylation of AKT (43%) and mTOR (93%) was observed at the 6 mg/kg dose level of Xe-liposomes, while these biomarkers and phosphorylated PKC and ERK1/2 levels remained unchanged at the higher dose. Moreover, Xe-liposomal treatment did not change the plasma and protein levels of BDNF, and phosphorylated AKT, mTOR, PKC and ERK1/2 hippocampal expressions.

CONCLUSION

Xe-liposomes mediate a rapid antidepressant-like effect through activation of AKT/mTOR/BDNF signaling pathway.

Are there advances in pharmacotherapy for panic disorder? A systematic review of the past five years

INTRODUCTION

Several effective medications are available for treating panic disorder (PD). However, outcomes are unsatisfactory in a number of patients, suggesting the usefulness of expanding the array of antipanic drugs and improving the quality of response to current recommended treatments.

AREAS COVERED

The authors have performed an updated systematic review of pharmacological studies (phase III onwards) to examine whether advances have been made in the last five years. Only four studies were included. D-cycloserine no longer seemed promising as a cognitive-behavioral therapy (CBT) enhancer. Some preliminary findings concerning the optimization of recommended medications deserved consideration, including: the possibility that SSRIs are more effective than CBT alone in treating panic attacks, combined therapy is preferable when agoraphobia is present, and clonazepam is more potent than paroxetine in decreasing panic relapse.

EXPERT OPINION

Given the lack of novel treatments, expanding a personalized approach to the existing medications seems to be the most feasible strategy to improve pharmacotherapy outcomes regarding PD. Recent technological progress, including wearable devices collecting real-time data, 'big data' platforms, and application of machine learning techniques might help make outcome prediction more reliable. Further research on previously promising novel treatments is also recommended.