Cannabinoid receptors on peripheral leukocytes from patients with schizophrenia: Evidence for defective immunomodulatory mechanisms

Endocannabinoid system alterations in schizophrenia: association with cannabis use and antipsychotic medication

Determining peripheral modulation of the endocannabinoid system (ECS) may be important for differentiating individuals with schizophrenia. Such differentiation can also be extended to subgroups of individuals, those who use cannabis and antipsychotic medications, particularly those who are treatment resistant. Patients and controls were recruited from the outpatient clinic of the Psychosis Group of the University of São Paulo, Brazil. A final sample of 93 individuals was divided into 3 groups: patients with schizophrenia using clozapine (treatment-resistant) (n = 29), patients with schizophrenia using another antipsychotic (n = 31), and controls (n = 33). By measuring the proteins and metabolites involved in the ECS pathways in the peripheral blood, AEA (anandamide), 2-AG (2-arachidonoyl ethanolamine), and CB2 receptor (peripheral) were quantified. Individuals reporting lifetime cannabis use had lower 2-AG plasma levels (p = 0.011). Regarding the CB2 receptor, the values of patients with schizophrenia and controls were similar, but those of patients using antipsychotics other than clozapine differed (p = 0.022). In generalized linear models to control for confounders, the use of cannabis remained the only factor that significantly influenced 2-AG levels. The relationship for non-clozapine antipsychotics as the only factor related to CB2 changes was marginally significant. We found for the first time that cannabis use and non-clozapine antipsychotic medication are potentially involved in the modulation of the ECS, specifically influencing 2-AG endocannabinoid and CB2 receptor levels. More studies regarding the ECS are needed since it has been increasingly related to the physiopathology of schizophrenia.

Peripheral Endocannabinoid Components and Lipid Plasma Levels in Patients with Resistant Migraine and Co-Morbid Personality and Psychological Disorders: A Cross-Sectional Study

Resistant migraine characterizes those patients who have failed at least three classes of migraine prophylaxis. These difficult-to-treat patients are likely to be characterized by a high prevalence of psychological disturbances. A dysfunction of the endocannabinoid system (ECS), including alteration in the levels of endocannabinoid congeners, may underlie several psychiatric disorders and the pathogenesis of migraines. Here we explored whether the peripheral gene expression of major components of the ECS and the plasma levels of endocannabinoids and related lipids are associated with psychological disorders in resistant migraine. Fifty-one patients (age = 46.0 ± 11.7) with resistant migraine received a comprehensive psychological evaluation according to the DSM-5 criteria. Among the patients, 61% had personality disorders (PD) and 61% had mood disorders (MD). Several associations were found between these psychological disorders and peripheral ECS alterations. Lower plasma levels of palmitoiletanolamide (PEA) were found in the PD group compared with the non-PD group. The MD group was characterized by lower mRNA levels of diacylglycerol lipase α (DAGLα) and CB2 (cannabinoid-2) receptor. The results suggest the existence of peripheral dysfunction in some components of the ECS and an alteration in plasma levels of PEA in patients with resistant migraine and mood or personality disorders.

Hematological and inflammatory markers in Han Chinese patients with drug-free schizophrenia: relationship with symptom severity

Background

There is a growing amount of evidence suggesting that immunity and inflammation play an important role in the pathophysiology of schizophrenia. In this study, we aimed to examine the relationship between hematological and inflammatory markers with symptom severity in Han Chinese patients with drug-free schizophrenia.

Methods

This retrospective study was conducted at Chaohu Hospital of Anhui Medical University and data were extracted from the electronic medical record system over a 5-year period (May 2017 to April 2022), including participants' general and clinical information as well as Brief Psychiatric Rating Scale (BPRS) scores and hematological parameters.

Results

A total of 2,899 patients with schizophrenia were identified through the initial search. After screening, 91 patients and 141 healthy controls (HCs) were included. The patients had a higher value of neutrophils/lymphocytes ratio (NLR), monocyte/lymphocyte ratio (MLR), and platelet/lymphocyte ratio (PLR) than HCs (all P < 0.001). MLR was positively correlated with BPRS total score (r = 0.337, P = 0.001) and resistance subscale score (r = 0.350, P = 0.001). Binary logistic regression analyses revealed that severely ill was significantly associated with being male and a higher value of MLR (Natural Logaruthm, Ln) (all P < 0.05), and the receiver operating characteristic (ROC) analysis showed good performance of a regression model with an area under the curve (AUC) value of 0.787.

Conclusion

Patients with drug-free schizophrenia have an unbalanced distribution of peripheral blood granulocytes, and elevated NLR, MLR and PLR. Patients with higher value of MLR tend to have more psychotic symptoms, especially those symptoms of hostility, uncooperativeness, and suspiciousness. Our study gives a preliminary indication that MLR is a potential predictor of disease severity in patients with drug-free schizophrenia.

Microglia and Other Cellular Mediators of Immunological Dysfunction in Schizophrenia: A Narrative Synthesis of Clinical Findings

Schizophrenia is a complex psychiatric condition that may involve immune system dysregulation. Since most putative disease mechanisms in schizophrenia have been derived from genetic association studies and fluid-based molecular analyses, this review aims to summarize the emerging evidence on clinical correlates to immune system dysfunction in this psychiatric disorder. We conclude this review by attempting to develop a unifying hypothesis regarding the relative contributions of microglia and various immune cell populations to the development of schizophrenia. This may provide important translational insights that can become useful for addressing the multifaceted clinical presentation of schizophrenia.

Cannabis use selectively modulates circulating biomarkers in the blood of schizophrenia patients

Cannabis use disorder is frequent in schizophrenia patients, and it is associated with an earlier age of onset and poor schizophrenia prognosis. Serotonin 2A receptors (5-HT2AR) have been involved in psychosis and, like Akt kinase, are known to be modulated by THC. Likewise, endocannabinoid system dysregulation has been suggested in schizophrenia. The presence of these molecules in blood makes them interesting targets, as they can be evaluated in patients by a minimally invasive technique. The aim of the present study was to evaluate 5-HT2AR protein expression and the Akt functional status in platelet homogenates of subjects diagnosed with schizophrenia, cannabis use disorder, or both conditions, compared with age- and sex-matched control subjects. Additionally, endocannabinoids and pro-inflammatory interleukin-6 (IL-6) levels were also measured in the plasma of these subjects. Results showed that both platelet 5-HT2AR and the active phospho (Ser473)Akt protein expression were significantly increased in schizophrenia subjects, whereas patients with a dual diagnosis of schizophrenia and cannabis use disorder did not show significant changes. Similarly, plasma concentrations of anandamide and other lipid mediators such as PEA and DEA, as well as the pro-inflammatory IL-6, were significantly increased in schizophrenia, but not in dual subjects. Results demonstrate that schizophrenia subjects show different circulating markers pattern depending on the associated diagnosis of cannabis use disorder, supporting the hypothesis that there could be different underlying mechanisms that may explain clinical differences among these groups. Moreover, they provide the first preliminary evidence of peripherally measurable molecules of interest for bigger prospective studies in these subpopulations.

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.

Involvement of anti-inflammatory, antioxidant, and BDNF up-regulating properties in the antipsychotic-like effect of the essential oil of Alpinia zerumbet in mice: a comparative study with olanzapine

The current drug therapy for schizophrenia effectively treats acute psychosis and its recurrence; however, this mental disorder's cognitive and negative symptoms are still poorly controlled. Antipsychotics present important side effects, such as weight gain and extrapyramidal effects. The essential oil of Alpinia zerumbet (EOAZ) leaves presents potential antipsychotic properties that need further preclinical investigation. Here, we determined EAOZ effects in preventing and reversing schizophrenia-like symptoms (positive, negative, and cognitive) induced by ketamine (KET) repeated administration in mice and putative neurobiological mechanisms related to this effect. We conducted the behavioral evaluations of prepulse inhibition of the startle reflex (PPI), social interaction, and working memory (Y-maze task), and verified antioxidant (GSH, nitrite levels), anti-inflammatory [interleukin (IL)-6], and neurotrophic [brain-derived neurotrophic factor (BDNF)] effects of this oil in hippocampal tissue. The atypical antipsychotic olanzapine (OLZ) was used as standard drug therapy. EOAZ, similarly to OLZ, prevented and reversed most KET-induced schizophrenia-like behavioral alterations, i.e., sensorimotor gating deficits and social impairment. EOAZ had a modest effect on the prevention of KET-associated working memory deficit. Compared to OLZ, EOAZ showed a more favorable side effects profile, inducing less cataleptic and weight gain changes. EOAZ efficiently protected the hippocampus against KET-induced oxidative imbalance, IL-6 increments, and BDNF impairment. In conclusion, our data add more mechanistic evidence for the anti-schizophrenia effects of EOAZ, based on its antioxidant, anti-inflammatory, and BDNF up-regulating actions. The absence of significant side effects observed in current antipsychotic drug therapy seems to be an essential benefit of the oil.

Endocannabinoid system in psychotic and mood disorders, a review of human studies

Despite widespread evidence of endocannabinoid system involvement in the pathophysiology of psychiatric disorders, our understanding remains rudimentary. Here we review studies of the endocannabinoid system in humans with psychotic and mood disorders. Postmortem, peripheral, cerebrospinal fluid and in vivo imaging studies provide evidence for the involvement of the endocannabinoid system in psychotic and mood disorders. Psychotic disorders and major depressive disorder exhibit alterations of brain cannabinoid CB1 receptors and peripheral blood endocannabinoids. Further, these changes may be sensitive to treatment status, disease state, and symptom severity. Evidence from psychotic disorder extend to endocannabinoid metabolizing enzymes in the brain and periphery, whereas these lines of evidence remain poorly developed in mood disorders. A paucity of studies examining this system in bipolar disorder represents a notable gap in the literature. Despite a growing body of productive work in this field of research, there is a clear need for investigation beyond the CB1 receptor in order to more fully elucidate the role of the endocannabinoid system in psychotic and mood disorders.

A pilot study of biomarkers of oxidative stress in serum and schizophrenia

Increasing evidence indicates that oxidative damage and inflammation is present in patients with schizophrenia. In this study, we investigated the association between the serum concentrations of four typical oxidative stress and inflammatory biomarkers (monocyte chemotactic protein-1, heme oxygenase-1, interleukin-8, and 8-Hydroxydeoxyguanine) and schizophrenia using a case-control study design. In total, 44 patients with schizophrenia and 45 normal controls from Shandong Province, China were recruited. Fasting blood samples were collected from all participants and the serum concentration of the four biomarkers were analyzed by Enzyme-linked immunosorbent assay. The concentrations of monocyte chemotactic protein-1 and interleukin-8 were significantly higher in the patients than in the controls, while there was no significant difference in the serum concentrations of heme oxygenase-1 and 8-Hydroxydeoxyguanine. Moreover, the serum concentrations of monocyte chemotactic protein-1 and interleukin-8 in patients were positively correlated with severity of clinical symptoms. Dose-response relationships between serum biomarker concentrations and schizophrenia were observed. This study suggests that levels of monocyte chemotactic protein-1 and interleukin-8 are increased in patients with schizophrenia and correlated with positive symptom severity.

Biomarkers in Psychiatry: Concept, Definition, Types and Relevance to the Clinical Reality

During the last years, an extraordinary effort has been made to identify biomarkers as potential tools for improving prevention, diagnosis, drug response and drug development in psychiatric disorders. Contrary to other diseases, mental illnesses are classified by diagnostic categories with a broad variety list of symptoms. Consequently, patients diagnosed from the same psychiatric illness present a great heterogeneity in their clinical presentation. This fact together with the incomplete knowledge of the neurochemical alterations underlying mental disorders, contribute to the limited efficacy of current pharmacological options. In this respect, the identification of biomarkers in psychiatry is becoming essential to facilitate diagnosis through the developing of markers that allow to stratify groups within the syndrome, which in turn may lead to more focused treatment options. In order to shed light on this issue, this review summarizes the concept and types of biomarkers including an operational definition for therapeutic development. Besides, the advances in this field were summarized and sorted into five categories, which include genetics, transcriptomics, proteomics, metabolomics, and epigenetics. While promising results were achieved, there is a lack of biomarker investigations especially related to treatment response to psychiatric conditions. This review includes a final conclusion remarking the future challenges required to reach the goal of developing valid, reliable and broadly-usable biomarkers for psychiatric disorders and their treatment. The identification of factors predicting treatment response will reduce trial-and-error switches of medications facilitating the discovery of new effective treatments, being a crucial step towards the establishment of greater personalized medicine.

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.

Kynurenines and the Endocannabinoid System in Schizophrenia: Common Points and Potential Interactions

Schizophrenia, which affects around 1% of the world’s population, has been described as a complex set of symptoms triggered by multiple factors. However, the exact background mechanisms remain to be explored, whereas therapeutic agents with excellent effectivity and safety profiles have yet to be developed. Kynurenines and the endocannabinoid system (ECS) play significant roles in both the development and manifestation of schizophrenia, which have been extensively studied and reviewed previously. Accordingly, kynurenines and the ECS share multiple features and mechanisms in schizophrenia, which have yet to be reviewed. Thus, the present study focuses on the main common points and potential interactions between kynurenines and the ECS in schizophrenia, which include (i) the regulation of glutamatergic/dopaminergic/γ-aminobutyric acidergic neurotransmission, (ii) their presence in astrocytes, and (iii) their role in inflammatory mechanisms. Additionally, promising pharmaceutical approaches involving the kynurenine pathway and the ECS will be reviewed herein.

Measuring Disturbance of the Endocannabinoid System in Psychosis: A Systematic Review and Meta-analysis

IMPORTANCE

The endocannabinoid system (ECS) is a lipid-based endogenous signaling system. Its relevance to psychosis is through the association between cannabis use and the onset and course of illness and through the antipsychotic properties of cannabidiol, a potential ECS enhancer.

OBJECTIVE

To conduct a systematic review and meta-analysis of the blood and cerebrospinal fluid (CSF) measures of the ECS in psychotic disorders.

DATA SOURCES

Web of Science and PubMed were searched from inception through June 13, 2018. The articles identified were reviewed, as were citations to previous publications and the reference lists of retrieved articles.

STUDY SELECTION

Original articles were included that reported blood or CSF measures of ECS activity in patients with psychotic illnesses and in healthy controls.

DATA EXTRACTION AND SYNTHESIS

PRISMA guidelines, independent extraction by multiple observers, and random-effects meta-analysis were used. Heterogeneity was assessed with the I2 index. Sensitivity analyses tested the robustness of the results.

MAIN OUTCOMES AND MEASURES

The clinical relevance of ECS modifications in psychotic disorders was investigated by (1) a quantitative synthesis of the differences in blood and CSF markers of the ECS between patients and healthy controls, and (2) a qualitative synthesis of the association of these markers with symptom severity, stage of illness, and response to treatment.

RESULTS

A total of 18 studies were included. Three individual meta-analyses were performed to identify the differences in ECS markers between people with schizophrenia and healthy controls. Five studies, including 226 patients and 385 controls, reported significantly higher concentrations of anandamide in the CSF of patients than controls (standardized mean difference [SMD], 0.97; 95% CI, 0.67-1.26; P < .001; I2 = 54.8%). In 9 studies, with 344 patients and 411 controls, significantly higher anandamide levels in blood were found in patients, compared with controls (SMD, 0.55; 95% CI, 0.05-1.04; P = .03; I2 = 89.6%). In 3 studies, involving 88 patients and 179 controls, a significantly higher expression of type 1 cannabinoid receptors on peripheral immune cells was reported in patients compared with controls (SMD, 0.57; 95% CI, 0.31-0.84; P < .001; I2 = 0%). Higher ECS tone was found at an early stage of illness in individuals who were antipsychotic naïve or free, and it had an inverse association with symptom severity and was normalized after successful treatment. Moderate to high level of heterogeneity in methods was found between studies.

CONCLUSIONS AND RELEVANCE

Testing clinically relevant markers of the ECS in the blood and CSF of people with psychotic illness appears possible, and these markers provide useful biomarkers for the psychotic disorder; however, not all studies accounted for important variables, such as cannabis use.

TRIAL REGISTRATION

PROSPERO identifier: CRD42018099863.

Increased peripheral levels of TARC/CCL17 in first episode psychosis patients

BACKGROUND

Evidence for a link between the pathophysiology of schizophrenia and the immune system is mounting. Altered levels of chemokines in plasma have previously been reported in patients with schizophrenia under antipsychotic medication. Here we aimed to study both peripheral and central chemokine levels in drug-naïve or short-time medicated first episode psychosis (FEP) patients.

METHOD

We analyzed nine chemokines in plasma and CSF from 41 FEP patients and 22 healthy controls using electrochemiluminescence assay.

RESULTS

In plasma four chemokines; TARC/CCL17, eotaxin/CCL11, MDC/CCL22, IP-10/CXCL10 and in CSF one chemokine; IP-10/CXCL10 showed reliable detection in >50% of the cases. FEP patients displayed increased levels of TARC/CCL17 in plasma compared to healthy controls, 89.6 (IQR 66.2-125.8) pg/mL compared to 48.6 (IQR 28.0-71.7) pg/mL (p = 0.001). The difference was not attributed to confounding factors. Plasma TARC/CCL17 was not associated with PANSS, CGI or GAF scores, neither with cognitive functions. The chemokines eotaxin/CCL11, MDC/CCL22, IP-10/CXCL10 in plasma and IP-10/CXCL10 in CSF did not differ between FEP patients and controls.

CONCLUSION

In line with a previous study showing that chronic patients with schizophrenia display increased plasma TARC/CCL17 levels, we here found an elevation in FEP patients suggesting a role of TARC/CCL17 in early stages of schizophrenia. The exact mechanism of this involvement is still unknown and future longitudinal studies as well as studies of central and peripheral chemokine levels would be of great interest.

Gene-environment interaction between an endocannabinoid system genetic polymorphism and cannabis use in first episode of psychosis

Alterations of the endocannabinoid system (ECS) may play an important role in the development of schizophrenia and other psychotic disorders. Cannabis use is one of the environmental factors more repeatedly related to an increase the risk of developing a psychotic episode, while its use modifies the ECS normal function. In the present study we purposed to examine the gene by environment (GxE) interaction between 15 selected single nucleotide polymorphisms (SNPs) related to the ECS and cannabis use in a cohort of 321 patients with a first episode of psychosis (FEP) and 241 matched healthy controls. We found the fatty-acid amide hydrolase (FAAH) rs2295633 SNP genetic polymorphism was associated with a greater risk of presenting a FEP in subjects with relevant cannabis use, but not in subjects without a history of cannabis use. The probability of presenting a FEP was tenfold higher (OR: 10.69) in cannabis users who were homozygote carriers of the T allele of the FAAH rs2295633 SNP, compared to users of cannabis without this genotype. We also found that a higher a proportion of TT carriers of the FAAH rs2295633 SNP with a positive history of cannabis use was treated with high potency antipsychotic. This study has identified a GxE-environment interaction between a genetic polymorphism from the ECS and cannabis use involved in the risk of presenting a FEP. Although this preliminary data should be replicated with independent samples, our results highlight the importance of the pro-psychotic effects of exogenous cannabis use over the ECS in certain subjects.

Cannabis, Cannabinoids, and the Endocannabinoid System-Is there Therapeutic Potential for Inflammatory Bowel Disease?

Cannabis sativa and its extracts have been used for centuries, both medicinally and recreationally. There is accumulating evidence that exogenous cannabis and related cannabinoids improve symptoms associated with inflammatory bowel disease [IBD], such as pain, loss of appetite, and diarrhoea. In vivo, exocannabinoids have been demonstrated to improve colitis, mainly in chemical models. Exocannabinoids signal through the endocannabinoid system, an increasingly understood network of endogenous lipid ligands and their receptors, together with a number of synthetic and degradative enzymes and the resulting products. Modulating the endocannabinoid system using pharmacological receptor agonists, genetic knockout models, or inhibition of degradative enzymes have largely shown improvements in colitis in vivo. Despite these promising experimental results, this has not translated into meaningful benefits for human IBD in the few clinical trials which have been conducted to date, the largest study being limited by poor medication tolerance due to the Δ9-tetrahydrocannabinol component. This review article synthesises the current literature surrounding the modulation of the endocannabinoid system and administration of exocannabinoids in experimental and human IBD. Findings of clinical surveys and studies of cannabis use in IBD are summarised. Discrepancies in the literature are highlighted together with identifying novel areas of interest.