Schizophrenia and depression, two poles of endocannabinoid system deregulation

NMDA glutamate receptor antagonist MK-801 induces proteome changes in adult human brain slices which are partially counteracted by haloperidol and clozapine

Deciphering the molecular pathways associated with N-methyl-D-aspartate receptor (NMDAr) hypofunction and its interaction with antipsychotics is necessary to advance our understanding of the basis of schizophrenia, as well as our capacity to treat this disease. In this regard, the development of human brain-derived models that are amenable to studying the neurobiology of schizophrenia may contribute to filling the gaps left by the widely employed animal models. Here, we assessed the proteomic changes induced by the NMDA glutamate receptor antagonist MK-801 on human brain slice cultures obtained from adult donors submitted to respective neurosurgery. Initially, we demonstrated that MK-801 diminishes NMDA glutamate receptor signaling in human brain slices in culture. Next, using mass-spectrometry-based proteomics and systems biology in silico analyses, we found that MK-801 led to alterations in proteins related to several pathways previously associated with schizophrenia pathophysiology, including ephrin, opioid, melatonin, sirtuin signaling, interleukin 8, endocannabinoid, and synaptic vesicle cycle. We also evaluated the impact of both typical and atypical antipsychotics on MK-801-induced proteome changes. Interestingly, the atypical antipsychotic clozapine showed a more significant capacity to counteract the protein alterations induced by NMDAr hypofunction than haloperidol. Finally, using our dataset, we identified potential modulators of the MK-801-induced proteome changes, which may be considered promising targets to treat NMDAr hypofunction in schizophrenia. This dataset is publicly available and may be helpful in further studies aimed at evaluating the effects of MK-801 and antipsychotics in the human brain.

Endocannabinoid levels in plasma and neurotransmitters in the brain: a preliminary report on patients with a psychotic disorder and healthy individuals

BACKGROUND

Interactions between the endocannabinoid system (ECS) and neurotransmitter systems might mediate the risk of developing a schizophrenia spectrum disorder (SSD). Consequently, we investigated in patients with SSD and healthy controls (HC) the relations between (1) plasma concentrations of two prototypical endocannabinoids (N-arachidonoylethanolamine [anandamide] and 2-arachidonoylglycerol [2-AG]) and (2) striatal dopamine synthesis capacity (DSC), and glutamate and y-aminobutyric acid (GABA) levels in the anterior cingulate cortex (ACC). As anandamide and 2-AG might reduce the activity of these neurotransmitters, we hypothesized negative correlations between their plasma levels and the abovementioned neurotransmitters in both groups.

METHODS

Blood samples were obtained from 18 patients and 16 HC to measure anandamide and 2-AG plasma concentrations. For all subjects, we acquired proton magnetic resonance spectroscopy scans to assess Glx (i.e. glutamate plus glutamine) and GABA + (i.e. GABA plus macromolecules) concentrations in the ACC. Ten patients and 14 HC also underwent [18F]F-DOPA positron emission tomography for assessment of striatal DSC. Multiple linear regression analyses were used to investigate the relations between the outcome measures.

RESULTS

A negative association between 2-AG plasma concentration and ACC Glx concentration was found in patients (p = 0.008). We found no evidence of other significant relationships between 2-AG or anandamide plasma concentrations and dopaminergic, glutamatergic, or GABAergic measures in either group.

CONCLUSIONS

Our preliminary results suggest an association between peripheral 2-AG and ACC Glx levels in patients.

DNA methylation and the opposing NMDAR dysfunction in schizophrenia and major depression disorders: a converging model for the therapeutic effects of psychedelic compounds in the treatment of psychiatric illness

Psychedelic compounds are being increasingly explored as a potential therapeutic option for treating several psychiatric conditions, despite relatively little being known about their mechanism of action. One such possible mechanism, DNA methylation, is a process of epigenetic regulation that changes gene expression via chemical modification of nitrogenous bases. DNA methylation has been implicated in the pathophysiology of several psychiatric conditions, including schizophrenia (SZ) and major depressive disorder (MDD). In this review, we propose alterations to DNA methylation as a converging model for the therapeutic effects of psychedelic compounds, highlighting the N-methyl D-aspartate receptor (NMDAR), a crucial mediator of synaptic plasticity with known dysfunction in both diseases, as an example and anchoring point. We review the established evidence relating aberrant DNA methylation to NMDAR dysfunction in SZ and MDD and provide a model asserting that psychedelic substances may act through an epigenetic mechanism to provide therapeutic effects in the context of these disorders.

Circulating Endocannabinoids and N-Acylethanolamines in Individuals with Cannabis Use Disorder-Preliminary Findings

BACKGROUND

Endocannabinoids and related N-acylethanolamines (NAEs) are bioactive lipids with important physiological functions and putative roles in mental health and addictions. Although chronic cannabis use is associated with endocannabinoid system changes, the status of circulating endocannabinoids and related NAEs in people with cannabis use disorder (CUD) is uncertain.

METHODS

Eleven individuals with CUD and 54 healthy non-cannabis using control participants (HC) provided plasma for measurement by high-performance liquid chromatography-mass spectrometry of endocannabinoids (2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (AEA)) and related NAE fatty acids (N-docosahexaenoylethanolamine (DHEA) and N-oleoylethanolamine (OEA)). Participants were genotyped for the functional gene variant of FAAH (rs324420, C385A) which may affect concentrations of AEA as well as other NAEs (OEA, DHEA).

RESULTS

In overnight abstinent CUD, AEA, OEA and DHEA concentrations were significantly higher (31-40%; p < 0.05) and concentrations of the endocannabinoid 2-AG were marginally elevated (55%, p = 0.13) relative to HC. There were no significant correlations between endocannabinoids/NAE concentrations and cannabis analytes, self-reported cannabis use frequency or withdrawal symptoms. DHEA concentration was inversely related with marijuana craving (r = -0.86; p = 0.001). Genotype had no significant effect on plasma endocannabinoids/NAE concentrations.

CONCLUSIONS

Our preliminary findings, requiring replication, might suggest that activity of the endocannabinoid system is elevated in chronic cannabis users. It is unclear whether this elevation is a compensatory response or a predating state. Studies examining endocannabinoids and NAEs during prolonged abstinence as well as the potential role of DHEA in craving are warranted.

Endocannabinoid and perceived stress: Association analysis of endocannabinoid levels in hair versus levels in plasma and urine

The endocannabinoid system is considered to play a role in a wide range of functions, including stress. Hair analysis of endocannabinoids presents a promising methodological advancement for the retrospective assessment of long-term cumulative endocannabinoid secretion. Despite promising pilot study results suggesting the usefulness of hair endocannabinoid assessments, it remains unclear whether hair endocannabinoid levels mirror systemic endocannabinoid levels accurately. Two independent studies were conducted to investigate to what extent hair endocannabinoid and N-Acylethanolamine levels reflect the systemic levels retrospectively. Endocannabinoid and N-Acylethanolamine levels were measured in 3 cm and 1 cm hair segments respectively, and compared with the averaged levels in multiple plasma samples collected during three months (Study I), and in multiple 24-hour urine samples collected over a month (Study II). In addition, the Perceived Stress Scale was used to assess the perceived stress throughout the studies. Against our hypothesis, no association was found between the endocannabinoid or N-Acylethanolamine levels in hair and plasma or urine. However, hair palmitoylethanolamide (PEA), oleoylethanolamide (OEA), and stearoylethanolamide (SEA) levels were positively correlated with perceived stress in Study I. The current findings suggest that hair endocannabinoid or N-Acylethanolamine levels might not accurately reflect the levels of peripheral circulating endocannabinoid or N-Acylethanolamine. Nevertheless, hair N-Acylethanolamine levels might emerge as a useful strategy in the study of some psychological phenotypes, such as stress.

Hallucinations and Hallucinogens: Psychopathology or Wisdom?

Hallucinations are currently associated almost exclusively with psychopathological states. While it is evident that hallucinations can indicate psychopathology or neurological disorders, we should remember that hallucinations also commonly occur in people without any signs of psychopathology. A similar case occurs in the case of hallucinogenic drugs, which have been long associated with psychopathology and insanity. However, during the last decades a huge body of research has shown that certain kinds of hallucinations, exerted by hallucinogenic drugs, may serve to improve mental health. We propose that, in light of historical, epidemiological, and scientific research, hallucinations can be better characterized as a common phenomenon associated sometimes with psychopathology but also with functional and even beneficial outcomes. In the last sections of the manuscript, we extend our argument, suggesting that hallucinations can offer a via regia to knowledge of the mind and the world. This radical shift in the cultural interpretation of hallucinations could have several implications for fields such as drug policy, civil law, and psychiatry, as well as for the stigma associated with mental disorders.

Genetic variables of the glutamatergic system associated with treatment-resistant depression: A review of the literature

Depression is a common, recurrent mental disorder and one of the leading causes of disability and global burden of disease worldwide. Up to 15%-40% of cases do not respond to diverse pharmacological treatments and, thus, can be defined as treatment-resistant depression (TRD). The development of biomarkers predictive of drug response could guide us towards personalized and earlier treatment. Growing evidence points to the involvement of the glutamatergic system in the pathogenesis of TRD. Specifically, the N-methyl-D-aspartic acid receptor (NMDAR) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), which are targeted by ketamine and esketamine, are proposed as promising pathways. A literature search was performed to identify studies on the genetics of the glutamatergic system in depression, focused on variables related to NMDARs and AMPARs. Our review highlights GRIN2B, which encodes the NR2B subunit of NMDAR, as a candidate gene in the pathogenesis of TRD. In addition, several studies have associated genes encoding AMPAR subunits with symptomatic severity and suicidal ideation. These genes encoding glutamatergic receptors could, therefore, be candidate genes for understanding the etiopathogenesis of TRD, as well as for understanding the pharmacodynamic mechanisms and response to ketamine and esketamine treatment.

Molecular Alterations of the Endocannabinoid System in Psychiatric Disorders

The therapeutic benefits of the current medications for patients with psychiatric disorders contrast with a great variety of adverse effects. The endocannabinoid system (ECS) components have gained high interest as potential new targets for treating psychiatry diseases because of their neuromodulator role, which is essential to understanding the regulation of many brain functions. This article reviewed the molecular alterations in ECS occurring in different psychiatric conditions. The methods used to identify alterations in the ECS were also described. We used a translational approach. The animal models reproducing some behavioral and/or neurochemical aspects of psychiatric disorders and the molecular alterations in clinical studies in post-mortem brain tissue or peripheral tissues were analyzed. This article reviewed the most relevant ECS changes in prevalent psychiatric diseases such as mood disorders, schizophrenia, autism, attentional deficit, eating disorders (ED), and addiction. The review concludes that clinical research studies are urgently needed for two different purposes: (1) To identify alterations of the ECS components potentially useful as new biomarkers relating to a specific disease or condition, and (2) to design new therapeutic targets based on the specific alterations found to improve the pharmacological treatment in psychiatry.

Inflammation and Nitro-oxidative Stress as Drivers of Endocannabinoid System Aberrations in Mood Disorders and Schizophrenia

The endocannabinoid system (ECS) is composed of the endocannabinoid ligands anandamide (AEA) and 2-arachidonoylgycerol (2-AG), their target cannabinoid receptors (CB₁ and CB₂) and the enzymes involved in their synthesis and metabolism (N-acyltransferase and fatty acid amide hydrolase (FAAH) in the case of AEA and diacylglycerol lipase (DAGL) and monoacylglycerol lipase (MAGL) in the case of 2-AG). The origins of ECS dysfunction in major neuropsychiatric disorders remain to be determined, and this paper explores the possibility that they may be associated with chronically increased nitro-oxidative stress and activated immune-inflammatory pathways, and it examines the mechanisms which might be involved. Inflammation and nitro-oxidative stress are associated with both increased CB₁ expression, via increased activity of the NADPH oxidases NOX4 and NOX1, and increased CNR1 expression and DNA methylation; and CB₂ upregulation via increased pro-inflammatory cytokine levels, binding of the transcription factor Nrf2 to an antioxidant response element in the CNR2 promoter region and the action of miR-139. CB₁ and CB₂ have antagonistic effects on redox signalling, which may result from a miRNA-enabled negative feedback loop. The effects of inflammation and oxidative stress are detailed in respect of AEA and 2-AG levels, via effects on calcium homeostasis and phospholipase A₂ activity; on FAAH activity, via nitrosylation/nitration of functional cysteine and/or tyrosine residues; and on 2-AG activity via effects on MGLL expression and MAGL. Finally, based on these detailed molecular neurobiological mechanisms, it is suggested that cannabidiol and dimethyl fumarate may have therapeutic potential for major depressive disorder, bipolar disorder and schizophrenia.

Habenula orphan G-protein coupled receptors in the pathophysiology of fear and anxiety

The phasic emotion, fear, and the tonic emotion, anxiety, have been conventionally inspected in clinical frameworks to epitomize memory acquisition, storage, and retrieval. However, inappropriate expression of learned fear in a safe environment and its resistance to suppression is a cardinal feature of various fear-related disorders. A significant body of literature suggests the involvement of extra-amygdala circuitry in fear disorders. Consistent with this view, the present review underlies incentives for the association between the habenula and fear memory. G protein-coupled receptors (GPCRs) are important to understand the molecular mechanisms central to fear learning due to their neuromodulatory role. The efficacy of a pharmacological strategy aimed at exploiting habenular-GPCR desensitization machinery can serve as a therapeutic target combating the pathophysiology of fear disorders. Originating from this milieu, the conserved nature of orphan GPCRs in the brain, with some having the highest expression in the habenula can lead to recent endeavors in understanding its functionality in fear circuitry.

The σ1 Receptor and the HINT1 Protein Control α2δ1 Binding to Glutamate NMDA Receptors: Implications in Neuropathic Pain

Nerve injury produces neuropathic pain through the binding of α2δ1 proteins to glutamate N-methyl-D-aspartate receptors (NMDARs). Notably, mice with a targeted deletion of the sigma 1 receptor (σ1R) gene do not develop neuropathy, whereas mice lacking the histidine triad nucleotide-binding protein 1 (Hint1) gene exhibit exacerbated allodynia. σ1R antagonists more effectively diminish neuropathic pain of spinal origin when administered by intracerebroventricular injection than systemically. Thus, in mice subjected to unilateral sciatic nerve chronic constriction injury (CCI), we studied the participation of σ1Rs and HINT1 proteins in the formation of α2δ1-NMDAR complexes within the supraspinal periaqueductal gray (PAG). We found that δ1 peptides required σ1Rs in order to interact with the NMDAR NR1 variant that contains the cytosolic C1 segment. σ1R antagonists or low calcium levels provoke the dissociation of σ1R-NR1 C1 dimers, while they barely affect the integrity of δ1-σ1R-NR1 C1 trimers. However, HINT1 does remove δ1 peptides from the trimer, thereby facilitating the subsequent dissociation of σ1Rs from NMDARs. In σ1R-/- mice, CCI does not promote the formation of NMDAR-α2δ1 complexes and allodynia does not develop. The levels of α2δ1-σ1R-NMDAR complexes increase in HINT1-/- mice and after inducing CCI, degradation of α2δ1 proteins is observed. Notably, σ1R antagonists but not gabapentinoids alleviate neuropathic pain in these mice. During severe neuropathy, the metabolism of α2δ1 proteins may account for the failure of many patients to respond to gabapentinoids. Therefore, σ1Rs promote and HINT1 proteins hinder the formation α2δ1-NMDAR complexes in the PAG, and hence, the appearance of mechanical allodynia depends on the interplay between these proteins.

A Multiscale View of the Mechanisms Underlying Ketamine's Antidepressant Effects: An Update on Neuronal Calcium Signaling

Major depressive disorder (MDD) is a debilitating disease characterized by depressed mood, loss of interest or pleasure, suicidal ideation, and reduced motivation or hopelessness. Despite considerable research, mechanisms underlying MDD remain poorly understood, and current advances in treatment are far from satisfactory. The antidepressant effect of ketamine is among the most important discoveries in psychiatric research over the last half-century. Neurobiological insights into the ketamine’s effects have shed light on the mechanisms underlying antidepressant efficacy. However, mechanisms underlying the rapid and sustained antidepressant effects of ketamine remain controversial. Elucidating such mechanisms is key to identifying new therapeutic targets and developing therapeutic strategies. Accumulating evidence demonstrates the contribution of the glutamatergic pathway, the major excitatory neurotransmitter system in the central nervous system, in MDD pathophysiology and antidepressant effects. The hypothesis of a connection among the calcium signaling cascade stimulated by the glutamatergic system, neural plasticity, and epigenetic regulation of gene transcription is further supported by its associations with ketamine’s antidepressant effects. This review briefly summarizes the potential mechanisms of ketamine’s effects with a specific focus on glutamatergic signaling from a multiscale perspective, including behavioral, cellular, molecular, and epigenetic aspects, to provide a valuable overview of ketamine’s antidepressant effects.

[Depression in the structure of schizophrenia: clinical and biochemical characteristics]

THE AIM OF THE STUDY

Was to investigate clinical and biochemical correlates of depression in the structure of schizophrenia to improve its diagnosis and differential diagnosis and to deepen understanding of mechanisms of schizophrenia development. Material and Methods. Forty-two inpatients at the stabilization stage of paranoid schizophrenia, aged 29.5±5.9 years, of whom 64.3% were women, were examined. The duration of the disease was 5.6±6.3 years. We used clinical and psychopathological methods, clinical scales (PANSS, SANS, BACS, Calgary Scale), catamnestic and clinic-laboratory methods (determination of brain-derived neurotrophic factor BDNF, proinflammatory cytokine interleukin-6, C-reactive protein). Results. At the stabilization stage, depression in patients with paranoid schizophrenia occurred in 19% of cases, more frequently in women. Female patients were more severely depressed, which was associated with an increased concentration of C-reactive protein, while negative symptoms predominated in male patients as compared to females. The presence of depression correlates with a lower severity of psychopathological, primarily positive symptoms and with a greater severity of neurocognitive deficit in schizophrenic patients. BDNF level directly correlates with the severity of positive and negative symptoms, and the level of interleukin 6 at the stage of remission formation does not differ from that in healthy individuals. C-reactive protein levels are associated with the characteristics of the course of schizophrenia.

Inverse correlation between plasma 2-arachidonoylglycerol levels and subjective severity of depression

OBJECTIVE

Endocannabinoids have been implicated in the pathophysiology of Major Depressive Disorder (MDD) and might represent potential targets for therapeutic intervention. Objectives of the study were: (1) to measure plasma levels of endocannabinoids in a group of antidepressant-free depressed outpatients; (2) to explore their relationship with the severity of depressive symptoms as subjectively perceived by the patients; and (3) to investigate the effect of the selective serotonin reuptake inhibitor escitalopram on endocannabinoid levels.

METHODS

We measured plasma levels of the two major endocannabinoids, 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (anadamide), in 12 drug-free outpatients diagnosed with MDD and in 12 matched healthy controls. In the patient group, endocannabinoids plasma levels were assessed at baseline and after 2 months of treatment with escitalopram.

RESULTS

Baseline plasma levels of the two endocannabinoids did not differ between depressed patients and healthy controls. However, there was a significant inverse correlation between 2-arachidonoylglycerol levels and the severity of subjectively perceived depressive symptoms. Treatment with escitalopram did not change endocannabinoid levels in depressed patients, although it caused the expected improvement of depressive symptoms.

CONCLUSIONS

Our results suggest that 2-arachidonylglycerol, the most abundant endocannabinoid in the central nervous system, might act to mitigate depressive symptoms, and raise the interesting possibility that 2-arachidonylglycerol and anandamide are differentially regulated in patients affected by MDD. Also, our data suggest but do not prove that the endocannabinoid system is not regulated by serotonergic transmission, at least in depressed patients.

A Characterization of the Effects of Minocycline Treatment During Adolescence on Structural, Metabolic, and Oxidative Stress Parameters in a Maternal Immune Stimulation Model of Neurodevelopmental Brain Disorders

BACKGROUND

Minocycline (MIN) is a tetracycline with antioxidant, anti-inflammatory, and neuroprotective properties. Given the likely involvement of inflammation and oxidative stress (IOS) in schizophrenia, MIN has been proposed as a potential adjuvant treatment in this pathology. We tested an early therapeutic window, during adolescence, as prevention of the schizophrenia-related deficits in the maternal immune stimulation (MIS) animal model.

METHODS

On gestational day 15, Poly I:C or vehicle was injected in pregnant Wistar rats. A total 93 male offspring received MIN (30 mg/kg) or saline from postnatal day (PND) 35-49. At PND70, rats were submitted to the prepulse inhibition test. FDG-PET and T2-weighted MRI brain studies were performed at adulthood. IOS markers were evaluated in frozen brain tissue.

RESULTS

MIN treatment did not prevent prepulse inhibition test behavioral deficits in MIS offspring. However, MIN prevented morphometric abnormalities in the third ventricle but not in the hippocampus. Additionally, MIN reduced brain metabolism in cerebellum and increased it in nucleus accumbens. Finally, MIN reduced the expression of iNOS (prefrontal cortex, caudate-putamen) and increased the levels of KEAP1 (prefrontal cortex), HO1 and NQO1 (amygdala, hippocampus), and HO1 (caudate-putamen).

CONCLUSIONS

MIN treatment during adolescence partially counteracts volumetric abnormalities and IOS deficits in the MIS model, likely via iNOS and Nrf2-ARE pathways, also increasing the expression of cytoprotective enzymes. However, MIN treatment during this peripubertal stage does not prevent sensorimotor gating deficits. Therefore, even though it does not prevent all the MIS-derived abnormalities evaluated, our results suggest the potential utility of early treatment with MIN in other schizophrenia domains.

The endocannabinoidome in neuropsychiatry: Opportunities and potential risks

The endocannabinoid system (ECS) comprises two cognate endocannabinoid receptors referred to as CB1R and CB2R_. ECS dysregulation is apparent in neurodegenerative/neuro-psychiatric disorders including but not limited to schizophrenia, major depressive disorder and potentially bipolar disorder. The aim of this paper is to review mechanisms whereby both receptors may interact with neuro-immune and neuro-oxidative pathways, which play a pathophysiological role in these disorders. CB1R is located in the presynaptic terminals of GABAergic, glutamatergic, cholinergic, noradrenergic and serotonergic neurons where it regulates the retrograde suppression of neurotransmission. CB1R plays a key role in long-term depression, and, to a lesser extent, long-term potentiation, thereby modulating synaptic transmission and mediating learning and memory. Optimal CB1R activity plays an essential neuroprotective role by providing a defense against the development of glutamate-mediated excitotoxicity, which is achieved, at least in part, by impeding AMPA-mediated increase in intracellular calcium overload and oxidative stress. Moreover, CB1R activity enables optimal neuron-glial communication and the function of the neurovascular unit. CB2R receptors are detected in peripheral immune cells and also in central nervous system regions including the striatum, basal ganglia, frontal cortex, hippocampus, amygdala as well as the ventral tegmental area. CB2R upregulation inhibits the presynaptic release of glutamate in several brain regions. CB2R activation also decreases neuroinflammation partly by mediating the transition from a predominantly neurotoxic "M1" microglial phenotype to a more neuroprotective "M2" phenotype. CB1R and CB2R are thus novel drug targets for the treatment of neuro-immune and neuro-oxidative disorders including schizophrenia and affective disorders.

Involvement of Chaperone Sigma1R in the Anxiolytic Effect of Fabomotizole

Sigma-1 receptor (chaperone Sigma1R) is an intracellular protein with chaperone functions, which is expressed in various organs, including the brain. Sigma1R participates in the regulation of physiological mechanisms of anxiety (Su, T. P. et al., 2016) and reactions to emotional stress (Hayashi, T., 2015). In 2006, fabomotizole (ethoxy-2-[2-(morpholino)-ethylthio]benzimidazole dihydrochloride) was registered in Russia as an anxiolytic (Seredenin S. and Voronin M., 2009). The molecular targets of fabomotizole are Sigma1R, NRH: quinone reductase 2 (NQO2), and monoamine oxidase A (MAO-A) (Seredenin S. and Voronin M., 2009). The current study aimed to clarify the dependence of fabomotizole anxiolytic action on its interaction with Sigma1R and perform a docking analysis of fabomotizole interaction with Sigma1R. An elevated plus maze (EPM) test revealed that the anxiolytic-like effect of fabomotizole (2.5 mg/kg i.p.) administered to male BALB/c mice 30 min prior EPM exposition was blocked by Sigma1R antagonists BD-1047 (1.0 mg/kg i.p.) and NE-100 (1.0 mg/kg i.p.) pretreatment. Results of initial in silico study showed that fabomotizole locates in the active center of Sigma1R, reproducing the interactions with the site's amino acids common for established Sigma1R ligands, with the ΔGbind value closer to that of agonist (+)-pentazocine in the 6DK1 binding site.

Mini-review: The therapeutic role of cannabinoids in neuroHIV

In the era of combined antiretroviral therapy (cART), human immunodeficiency virus type 1 (HIV-1) is considered a chronic disease with an inflammatory component that specifically targets the brain and causes a high prevalence of HIV-1-associated neurocognitive disorders (HAND). The endocannabinoid (eCB) system has attracted interest as a target for treatment of neurodegenerative disorders, due to the potential anti-inflammatory and neuroprotective properties of cannabinoids, including its potential therapeutic use in HIV-1 neuropathogenesis. In this review, we summarize what is currently known about the structural and functional changes of the eCB system under conditions of HAND. This will be followed by summarizing the current clinical and preclinical findings on the effects of cannabis use and cannabinoids in the context of HIV-1 infection, with specifically focusing on viral load, cognition, inflammation, and neuroprotection. Lastly, we present some potential future directions to better understand the involvement of the eCB system and the role that cannabis use and cannabinoids play in neuroHIV.

Endogenous antagonists of N-methyl-d-aspartate receptor in schizophrenia

Schizophrenia is a chronic neuropsychiatric brain disorder that has devastating personal impact and rising healthcare costs. Dysregulation of glutamatergic neurotransmission has been implicated in the pathobiology of the disease, attributed largely to the hypofunction of the N-methyl-d-aspartate (NMDA) receptor. Currently, there is a major gap in mechanistic analysis as to how endogenous modulators of the NMDA receptors contribute to the onset and progression of the disease. We present a systematic review of the neurobiology and the role of endogenous NMDA receptor antagonists in animal models of schizophrenia, and in patients. We discuss their neurochemical origin, release from neurons and glia with action mechanisms, and functional effects, which might contribute toward the impairment of neuronal processes underlying this complex pathological state. We consider clinical evidence suggesting dysregulations of endogenous NMDA receptor in schizophrenia, and highlight the pressing need in future studies and emerging directions, to restore the NMDA receptor functions for therapeutic benefits.

Beyond the Mind-Serum Trace Element Levels in Schizophrenic Patients: A Systematic Review

The alterations in serum trace element levels are common phenomena observed in patients with different psychiatric conditions such as schizophrenia, autism spectrum disorder, or major depressive disorder. The fluctuations in the trace element concentrations might act as potential diagnostic and prognostic biomarkers of many psychiatric and neurological disorders. This paper aimed to assess the alterations in serum trace element concentrations in patients with a diagnosed schizophrenia. The authors made a systematic review, extracting papers from the PubMed, Web of Science, and Scopus databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Among 5009 articles identified through database searching, 59 of them were assessed for eligibility. Ultimately, 33 articles were included in the qualitative synthesis. This review includes the analysis of serum levels of the following trace elements: iron, nickel, molybdenum, phosphorus, lead, chromium, antimony, uranium, magnesium, aluminum, zinc, copper, selenium, calcium, and manganese. Currently, there is no consistency regarding serum trace element levels in schizophrenic patients. Thus, it cannot be considered as a reliable prognostic or diagnostic marker of schizophrenia. However, it can be assumed that altered concentrations of those elements are crucial regarding the onset and exaggeration of either psychotic or negative symptoms or cognitive dysfunctions.

Regulation of cannabinoid CB1 and CB2 receptors, neuroprotective mTOR and pro-apoptotic JNK1/2 kinases in postmortem prefrontal cortex of subjects with major depressive disorder

BACKGROUND

Dysregulations of endocannabinoids and/or cannabinoid (CB) receptors have been implicated in the pathophysiology and treatment of major depressive disorder (MDD).

METHODS

CB₁ and CB₂ receptors, neuroprotective mTOR (mechanistic target of rapamycin) and pro-apoptotic JNK1/2 (c-Jun-N-terminal kinases) were quantified by immunoblotting in postmortem prefrontal cortex of MDD and controls, and further compared in antidepressant (AD)-free and AD-treated subjects. Neuroplastic proteins (PSD-95, Arc, spinophilin) were quantified in MDD brains.

RESULTS

Total cortical CB₁ glycosylated (≈54/64 kDa) receptor was increased in MDD (+20%, n=23, p=0.02) when compared with controls (100%, n=19). This CB₁ receptor upregulation was quantified in AD-treated (+23%, n=14, p=0.02) but not in AD-free (+14%, n=9, p=0.34) MDD subjects. In the same MDD cortical samples, CB₂ glycosylated (≈45 kDa) receptor was unaltered (all MDD: +11%, n=23, p=0.10; AD-free: +12%, n=9, p=0.31; AD-treated: +10%, n=14, p=0.23). In MDD, mTOR activity (p-Ser2448 TOR/t-TOR) was increased (all MDD: +29%, n=18, p=0.002; AD-free: +33%, n=8, p=0.03; AD-treated: +25%, n=10, p=0.04). In contrast, JNK1/2 activity (p-Thr183/Tyr185/t-JNK) was unaltered in MDD subjects. Cortical PSD-95, Arc, and spinophilin contents were unchanged in MDD.

LIMITATIONS

A relative limited sample size. Some MDD subjects had been treated with a variety of ADs. The results must be understood in the context of suicide victims with MDD.

CONCLUSIONS

The upregulation of CB₁ receptor density, but not that of CB₂ receptor, as well as the increased mTOR activity in PFC/BA9 of subjects with MDD (AD-free/treated) support their contributions in the complex pathophysiology of MDD and in the molecular mechanisms of antidepressant drugs.

Candidate Strategies for Development of a Rapid-Acting Antidepressant Class That Does Not Result in Neuropsychiatric Adverse Effects: Prevention of Ketamine-Induced Neuropsychiatric Adverse Reactions

Non-competitive N-methyl-D-aspartate/glutamate receptor (NMDAR) antagonism has been considered to play important roles in the pathophysiology of schizophrenia. In spite of severe neuropsychiatric adverse effects, esketamine (racemic enantiomer of ketamine) has been approved for the treatment of conventional monoaminergic antidepressant-resistant depression. Furthermore, ketamine improves anhedonia, suicidal ideation and bipolar depression, for which conventional monoaminergic antidepressants are not fully effective. Therefore, ketamine has been accepted, with rigorous restrictions, in psychiatry as a new class of antidepressant. Notably, the dosage of ketamine for antidepressive action is comparable to the dose that can generate schizophrenia-like psychotic symptoms. Furthermore, the psychotropic effects of ketamine precede the antidepressant effects. The maintenance of the antidepressive efficacy of ketamine often requires repeated administration; however, repeated ketamine intake leads to abuse and is consistently associated with long-lasting memory-associated deficits. According to the dissociative anaesthetic feature of ketamine, it exerts broad acute influences on cognition/perception. To evaluate the therapeutic validation of ketamine across clinical contexts, including its advantages and disadvantages, psychiatry should systematically assess the safety and efficacy of either short- and long-term ketamine treatments, in terms of both acute and chronic outcomes. Here, we describe the clinical evidence of NMDAR antagonists, and then the temporal mechanisms of schizophrenia-like and antidepressant-like effects of the NMDAR antagonist, ketamine. The underlying pharmacological rodent studies will also be discussed.

Brain NMDA Receptors in Schizophrenia and Depression

N-methyl-D-aspartate (NMDA) receptor antagonists such as phencyclidine (PCP), dizocilpine (MK-801) and ketamine have long been considered a model of schizophrenia, both in animals and humans. However, ketamine has been recently approved for treatment-resistant depression, although with severe restrictions. Interestingly, the dosage in both conditions is similar, and positive symptoms of schizophrenia appear before antidepressant effects emerge. Here, we describe the temporal mechanisms implicated in schizophrenia-like and antidepressant-like effects of NMDA blockade in rats, and postulate that such effects may indicate that NMDA receptor antagonists induce similar mechanistic effects, and only the basal pre-drug state of the organism delimitates the overall outcome. Hence, blockade of NMDA receptors in depressive-like status can lead to amelioration or remission of symptoms, whereas healthy individuals develop psychotic symptoms and schizophrenia patients show an exacerbation of these symptoms after the administration of NMDA receptor antagonists.

Can Physical Activity Support the Endocannabinoid System in the Preventive and Therapeutic Approach to Neurological Disorders?

The worldwide prevalence of neurological and neurodegenerative disorders, such as depression or Alzheimer's disease, has spread extensively throughout the last decades, becoming an enormous health issue. Numerous data indicate a distinct correlation between the altered endocannabinoid signaling and different aspects of brain physiology, such as memory or neurogenesis. Moreover, the endocannabinoid system is widely regarded as a crucial factor in the development of neuropathologies. Thus, targeting those disorders via synthetic cannabinoids, as well as phytocannabinoids, becomes a widespread research issue. Over the last decade, the endocannabinoid system has been extensively studied for its correlation with physical activity. Recent data showed that physical activity correlates with elevated endocannabinoid serum concentrations and increased cannabinoid receptor type 1 (CB1R) expression in the brain, which results in positive neurological effects including antidepressant effect, ameliorated memory, neuroplasticity development, and reduced neuroinflammation. However, none of the prior reviews presented a comprehensive correlation between physical activity, the endocannabinoid system, and neuropathologies. Thus, our review provides a current state of knowledge of the endocannabinoid system, its action in physical activity, as well as neuropathologies and a possible correlation between all those fields. We believe that this might contribute to finding a new preventive and therapeutic approach to both neurological and neurodegenerative disorders.

Ketamine's dose related multiple mechanisms of actions: Dissociative anesthetic to rapid antidepressant

Ketamine induces safe and effective anesthesia and displays unusual cataleptic properties that gave rise to the term dissociative anesthesia. Since 1970, clinicians only utilized the drug as an anesthetic or analgesic for decades, but ketamine was found to have rapid acting antidepressant effects in 1990s. Accumulated evidence exhibits NMDAR antagonism may not be the only mechanism of ketamine. The contributions of AMPA receptor, mTor signal pathway, monoaminergic system, sigma-1 receptor, cholinergic, opioid and cannabinoid systems, as well as voltage-gated calcium channels and hyperpolarization cyclic nucleotide gated channels are discussed for the antidepressant effects. Also the effects of ketamine's enantiomers and metabolites are reviewed. Furthermore ketamine's anesthetic and analgesic mechanisms are briefly revisited. Overall, pharmacology of ketamine, its enantiomers and metabolites is very unique. Insight into multiple mechanisms of action will provide further development and desirable clinical effects of ketamine.

Endocannabinoid System Components as Potential Biomarkers in Psychiatry

The high heterogeneity of psychiatric disorders leads to a lack of diagnostic precision. Therefore, the search of biomarkers is a fundamental aspect in psychiatry to reach a more personalized medicine. The endocannabinoid system (ECS) has gained increasing interest due to its involvement in many different functional processes in the brain, including the regulation of emotions, motivation, and cognition. This article reviews the role of the main components of the ECS as biomarkers in certain psychiatric disorders. Studies carried out in rodents evaluating the effects of pharmacological and genetic manipulation of cannabinoid receptors or endocannabinoids (eCBs) degrading enzymes were included. Likewise, the ECS-related alterations occurring at the molecular level in animal models reproducing some behavioral and/or neuropathological aspects of psychiatric disorders were reviewed. Furthermore, clinical studies evaluating gene or protein alterations in post-mortem brain tissue or in vivo blood, plasma, and cerebrospinal fluid (CSF) samples were analyzed. Also, the results from neuroimaging studies using positron emission tomography (PET) or functional magnetic resonance (fMRI) were included. This review shows the close involvement of cannabinoid receptor 1 (CB1r) in stress regulation and the development of mood disorders [anxiety, depression, bipolar disorder (BD)], in post-traumatic stress disorder (PTSD), as well as in the etiopathogenesis of schizophrenia, attention deficit hyperactivity disorder (ADHD), or eating disorders (i.e. anorexia and bulimia nervosa). On the other hand, recent results reveal the potential therapeutic action of the endocannabinoid tone manipulation by inhibition of eCBs degrading enzymes, as well as by the modulation of cannabinoid receptor 2 (CB2r) activity on anxiolytic, antidepressive, or antipsychotic associated effects. Further clinical research studies are needed; however, current evidence suggests that the components of the ECS may become promising biomarkers in psychiatry to improve, at least in part, the diagnosis and pharmacological treatment of psychiatric disorders.

Altered Swimming Behaviors in Zebrafish Larvae Lacking Cannabinoid Receptor 2

Background and Objectives: The cannabinoid receptor 2 (CB2) was previously implicated in brain functions, including complex behaviors. Here, we assessed the role of CB2 in selected swimming behaviors in zebrafish larvae and developed an in vivo upscalable whole-organism approach for CB2 ligand screening.

Experimental Approach: Using CRISPR-Cas9 technology, we generated a novel null allele (cnr2^upr1) and a stable homozygote-viable loss-of-function (CB2-KO) line. We measured in untreated wild-type and cnr2^upr1/upr1 larvae, photo-dependent (swimming) responses (PDR) and center occupancy (CO) to establish quantifiable anxiety-like parameters. Next, we measured PDR alteration and CO variation while exposing wild-type and mutant animals to an anxiolytic drug (valproic acid [VPA]) or to an anxiogenic drug (pentylenetetrazol [PTZ]). Finally, we treated wild-type and mutant larvae with two CB2-specific agonists (JWH-133 and HU-308) and two CB2-specific antagonists, inverse agonists (AM-630 and SR-144528).

Results: Untreated CB2-KO showed a different PDR than wild-type larvae as well as a decreased CO. VPA treatments diminished swimming activity in all animals but to a lesser extend in mutants. CO was strongly diminished and even more in mutants. PTZ-induced inverted PDR was significantly stronger in light and weaker in dark periods and the CO lower in PTZ-treated mutants. Finally, two of four tested CB2 ligands had a detectable activity in the assay.

Conclusions: We showed that larvae lacking CB2 behave differently in complex behaviors that can be assimilated to anxiety-like behaviors. Mutant larvae responded differently to VPA and PTZ treatments, providing in vivo evidence of CB2 modulating complex behaviors. We also established an upscalable combined genetic/behavioral approach in a whole organism that could be further developed for high-throughput drug discovery platforms.

Bupropion, a possible antidepressant without negative effects on alcohol relapse

RATIONALE

the role that antidepressants play on alcohol consumption is not well understood. Previous studies have reported that treatment with a Selective Serotonin Reuptake Inhibitor (SSRIs) increases alcohol consumption in an animal model of relapse, however it is unknown whether this effect holds for other antidepressants such as the atypical dopamine/norepinephrine reuptake inhibitors (SNDRI).

OBJECTIVES

the main goal of the present study was to compare the effects of two classes of antidepressants drugs, bupropion (SNDRI) and fluoxetine (SSRI), on alcohol consumption during relapse. Since glutamatergic and endocannabinoid signaling systems plays an important role in alcohol abuse and relapse, we also evaluated the effects of both antidepressants onthe expression of the main important genes and proteins of both systems in the prefrontal cortex, a critical brain region in alcohol relapse.

METHODS

rats were trained to self-administered alcohol. During abstinence, rats received a 14d-treatment with vehicle, fluoxetine (10 mg/kg) or bupropion (20 mg/kg), and we evaluated alcohol consumption during relapse for 3 weeks. Samples of prefrontal cortex were taken to evaluate the mRNA and protein expression of the different components of glutamatergic and endocannabinoid signaling systems.

RESULTS

fluoxetine treatment induced a long-lasting increase in alcohol consumption during relapse, an effect that was not observed in the case of bupropion treatment. The observed increases in alcohol consumption were accompanied by distinct alterations in the glutamate and endocannabinoid systems.

CONCLUSIONS

our results suggest that SSRIs can negatively impact alcohol consumption in relapse while SNDRIs have no effects. The observed increase in alcohol consumption are accompanied by functional alterations in the glutamatergic and endocannabinoid systems. This finding could open new strategies for the treatment of depression in patients with alcohol use disorders.

Cannabidiol enhances morphine antinociception, diminishes NMDA-mediated seizures and reduces stroke damage via the sigma 1 receptor

Cannabidiol (CBD), the major non-psychotomimetic compound present in the Cannabis sativa plant, exhibits therapeutic potential for various human diseases, including chronic neurodegenerative diseases, such as Alzheimer's and Parkinson's, ischemic stroke, epilepsy and other convulsive syndromes, neuropsychiatric disorders, neuropathic allodynia and certain types of cancer. CBD does not bind directly to endocannabinoid receptors 1 and 2, and despite research efforts, its specific targets remain to be fully identified. Notably, sigma 1 receptor (σ1R) antagonists inhibit glutamate N-methyl-D-aspartate acid receptor (NMDAR) activity and display positive effects on most of the aforesaid diseases. Thus, we investigated the effects of CBD on three animal models in which NMDAR overactivity plays a critical role: opioid analgesia attenuation, NMDA-induced convulsive syndrome and ischemic stroke. In an in vitro assay, CBD disrupted the regulatory association of σ1R with the NR1 subunit of NMDAR, an effect shared by σ1R antagonists, such as BD1063 and progesterone, and prevented by σ1R agonists, such as 4-IBP, PPCC and PRE084. The in vivo administration of CBD or BD1063 enhanced morphine-evoked supraspinal antinociception, alleviated NMDA-induced convulsive syndrome, and reduced the infarct size caused by permanent unilateral middle cerebral artery occlusion. These positive effects of CBD were reduced by the σ1R agonists PRE084 and PPCC, and absent in σ1R-/- mice. Thus, CBD displays antagonist-like activity toward σ1R to reduce the negative effects of NMDAR overactivity in the abovementioned experimental situations.