Antipsychotic treatment may alter T-helper (TH) 2 arm cytokines

Comparative Analysis of Serum BAFF and IL-17 Levels Pre- and Post-Antipsychotic Treatment for Acute Schizophrenia

The interplay between the cytokine network and antipsychotic treatment in schizophrenia remains poorly understood. This study aimed to investigate the impact of psychotropic medications on serum levels of IFN-γ, IL-4, TGF-β1, IL-17, and BAFF, and to explore their relationship with psychopathological features. We recruited 63 patients diagnosed with schizophrenia in the acute phase, all of whom were either drug-naïve or had been drug-free for at least three months. Serum levels of IL-4, IFN-γ, TGF-β1, IL-17, and BAFF were measured at baseline and after six months of antipsychotic treatment. The severity of symptoms was assessed using the Brief Psychiatric Rating Scale (BPRS), the Scale for the Assessment of Positive Symptoms (SAPS), and the Scale for the Assessment of Negative Symptoms (SANS). Fifty-two patients completed the six-month follow-up for immunoassay analysis. Antipsychotic treatment led to a significant decrease in serum levels of IFN-γ, TGF-β1, and IL-17, alongside a significant increase in BAFF levels. Changes in IFN-γ were positively correlated with SANS scores and negatively correlated with Global Assessment of Functioning (GAF) scores. Changes in TGF-β1 were negatively correlated with GAF scores. Changes in BAFF were negatively correlated with SAPS scores. Multivariable regression models were used to explore the association between cytokine level changes (IL-17, BAFF, IFN-γ, and TGF-β1) and independent variables, including demographic (gender, age), behavioral (tobacco use), clinical (schizophrenia type, disease course, date of onset, prior treatment), and biological (C-reactive protein (CRP), erythrocyte sedimentation rate (ESR)) factors, as well as standardized assessment scores. No significant associations were found, except for a significant negative correlation between TGF-β1 changes and GAF scores, as well as a positive correlation with age. Interestingly, advanced statistical analyses revealed that only changes in IL-17 and BAFF levels were significantly associated with antipsychotic treatment. Our findings suggest that antipsychotic drugs exert both pro- and anti-inflammatory effects on the cytokine network. The observed modulation of IL-17 and BAFF highlights their potential as future therapeutic targets in schizophrenia.

Association of cytokines levels, psychopathology and cognition among CR-TRS patients with metabolic syndrome

Clozapine-resistant treatment-refractory schizophrenia (CR-TRS) patients face significant clinical challenges. While links between metabolic syndrome (MetS) and inflammatory cytokines in schizophrenia have been established, the relationship between MetS and cytokine levels in CR-TRS patients remains unexplored. This study aimed to investigate the relationship between cytokines levels, clinical symptoms and cognitive impairments in CR-TRS patients, both with and without MetS. The study included 69 CR-TRS patients (31with MetS and 38 without MetS) and 84 healthy controls. The levels of IL-2, IL-6, TNF-α and routine biochemical parameters were measured. Psychopathological symptoms and cognitive function were assessed using the Positive and Negative Syndrome Scale (PANSS) and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), respectively. We found that CR-TRS patients with MetS displayed lower cognitive function scores compared to those without MetS, even when accounting for potential confounders. TNF-α levels were significantly higher in CRTRS patients with MetS compared to those without MetS, demonstrating substantial pathophysiological potential for CR-TRS patients with MetS via receiver operating characteristic curve (ROC). In CR-TRS patients without MetS, IL-2 independently contributed to the total score and general psychopathology subscore of PANSS. Additionally, IL-6 exhibited an independent contribution to the positive subscore of PANSS. In terms of cognition function, IL-6 independently contributed to the delayed memory of RBANS in CR-TRS patients without MetS. TNF-α could potentially serve as a predictive marker for distinguishing between CR-TRS patients with/without MetS, while IL-2 and IL-6 could independently contribute to psychopathological symptoms or cognitive function in CRTRS patients without MetS. Our study provided insights into the potential interplay between cytokines, clinical symptoms and cognitive impairments in CR-TRS patients with/without MetS.

Immunological Biomarkers as Predictors of Treatment Response in Psychotic Disorders

Psychotic disorders, notably schizophrenia, impose a detrimental burden on both an individual and a societal level. The mechanisms leading to psychotic disorders are multifaceted, with genetics and environmental factors playing major roles. Increasing evidence additionally implicates neuro-inflammatory processes within at least a subgroup of patients with psychosis. While numerous studies have investigated anti-inflammatory add-on treatments to current antipsychotics, the exploration of immunological biomarkers as a predictor of treatment response remains limited. This review outlines the current evidence from trials exploring the potential of baseline inflammatory biomarkers as predictors of the treatment effect of anti-inflammatory drugs as add-ons to antipsychotics and of antipsychotics alone. Several of the studies have found correlations between baseline immunological biomarkers and treatment response; however, only a few studies incorporated baseline biomarkers as a primary endpoint, and the findings thus need to be interpreted with caution. Our review emphasizes the need for additional research on the potential of repurposing anti-inflammatory drugs while utilizing baseline inflammatory biomarkers as a predictor of treatment response and to identify subgroups of individuals with psychotic disorders where add-on treatment with immunomodulating agents would be warranted. Future studies investigating the correlation between baseline inflammatory markers and treatment responses can pave the way for personalized medicine approaches in psychiatry centred around biomarkers such as specific baseline inflammatory biomarkers in psychotic disorders.

Anti-inflammatory effects of 2nd generation antipsychotics in patients with schizophrenia: A systematic review and meta-analysis

BACKGROUND

Schizophrenia is a major psychiatric disorder with unknown aetiology. Recent evidence suggests a potential role for cytokines in its pathophysiology and that antipsychotic medication may alter this. While the aetiology of schizophrenia remains only partly understood, an altered immune function representing an important avenue of further discovery. In this systematic review and meta-analysis we focus on the specific effects of second generation antipsychotics risperidone and clozapine on inflammatory cytokines.

METHODS

A defined systematic search of PubMed and Web of Science databases was performed to identify relevant studies published between Jan 1900 and May 2022. After screening of 2969 papers, 43 studies (27 single-arm and 8 dual-arm) were included that consisted of a total of 1421 patients with schizophrenia in the systematic review. From these, twenty studies (4 dual-arm; 678 patients) had data available on which a meta-analysis could be carried out.

RESULTS

Our meta-analysis showed a significant reduction of pro-inflammatory cytokines post-risperidone treatment in the absence of a similar association with clozapine. Subgroup analyses (First episode v chronic) demonstrated that duration of illness influenced the extent of cytokine alteration; risperidone treatment produced significant cytokine changes (lowered IL-6 and TNF-α) in chronic patients but not in first-episode psychosis (FEP) patients.

CONCLUSION

Varying treatment effects on cytokines can be observed by the use of different antipsychotic drugs. The cytokine alterations post-treatment are influenced by the specific antipsychotic drugs and patient status. This may explain disease progression in certain patient groups and influence therapeutic choices in the future.

Network Association of Biochemical and Inflammatory Abnormalities With Psychiatric Symptoms in First-Episode Schizophrenia Patients

BACKGROUND

Cardiovascular disease (CVD) risk factors such as dyslipidemia and systemic aberrant inflammatory processes may occur in patients with psychotic disorders, which may cause increased mortality. The interplay between immune and metabolic markers and its contribution to the clinical symptoms of schizophrenia (SCZ) remain unclear. This study aimed to examine the association of a series of inflammatory factors, plasma biochemical indicators, and SCZ clinical symptomatology with the severity of SCZ symptoms.

METHODS

A total of 115 participants, including 79 first-episode drug-naïve patients with SCZ and 36 healthy controls, were enrolled in this study. Semi-structured interviews were used to collect sociodemographic data, family history of SCZ, and medical and psychiatric history. The Brief Psychiatric Rating Scale (BPRS) and the Positive and Negative Syndrome Scale (PANSS) were administered by a clinical psychiatrist to evaluate the symptom severity of patients with SCZ. Plasma inflammatory cytokines were measured by a fully automated electrochemiluminescent immunoassay (Meso Scale Discovery).

RESULTS

Blood routine, biochemical, and inflammation cytokine test results showed that the levels of white blood cell count, neutrophil count, natrium, CRP, IL-8, IL-6, IL-13, and IL-16 significantly increased in the case group than in the healthy controls (p < 0.05), whereas levels of red blood cell count, hemoglobin concentration, mean corpuscular hemoglobin concentration, total protein, albumin, total bile acid, high-density lipoprotein (HDL), apolipoprotein A1, blood urea nitrogen, kalium and IL-15 were lower than in the healthy controls (p < 0.05). Correlation network analysis results shown that the natrium, HDL and red blood cell count were the top 3 factors closely to with BPRS and PANSS related clinical symptoms among of correlation network (degree = 4). ROC curve analysis explored the IL-16, IL-8, IL-13, IL-15, natrium, and HDL had highly sensitivity and specificity to the predictive validity and effectiveness for SCZ symptoms.

CONCLUSION

Our study revealed a complex interactive network correlation among the cardiovascular risk factors, biological immunity profiles, and psychotic symptoms in first-episode patients. Abnormal inflammatory factors and CVD risk factors had high sensitivity and specificity for predicting SCZ symptoms. Generally, our study provided novel information on the immune-related mechanisms involved in early CVD risk in patients with psychotic disorders.

Inflammation, hippocampal volume, and cognition in schizophrenia: results from the Northern Finland Birth Cohort 1966

Increased blood interleukin-6 (IL-6) levels are a replicated abnormality in schizophrenia, and may be associated with smaller hippocampal volumes and greater cognitive impairment. These findings have not been investigated in a population-based birth cohort. The general population Northern Finland Birth Cohort 1966 was followed until age 43. Subjects with schizophrenia were identified through the national Finnish Care Register. Blood IL-6 levels were measured in n = 82 subjects with schizophrenia and n = 5373 controls at age 31. Additionally, 31 patients with schizophrenia and 63 healthy controls underwent brain structural MRI at age 34, and cognitive testing at ages 34 and 43. Patients with schizophrenia had significantly higher median (interquartile range) blood IL-6 levels than controls (5.31, 0.85-17.20, versus 2.42, 0.54-9.36, p = 0.02) after controlling for potential confounding factors. In both schizophrenia and controls, higher blood IL-6 levels were predictors of smaller hippocampal volumes, but not cognitive performance at age 34. We found evidence for increased IL-6 levels in patients with midlife schizophrenia from a population-based birth cohort, and replicated associations between IL-6 levels and hippocampal volumes. Our results complement and extend the previous findings, providing additional evidence that IL-6 may play a role in the pathophysiology of schizophrenia and associated brain alterations.

Effect of risperidone treatment on insulin-like growth factor-1 and interleukin-17 in drug naïve first-episode schizophrenia

Increasing evidence suggests that the inflammatory system is activated in schizophrenia and antipsychotics may affect cytokines levels. we conducted a cross-sectional and prospective study.One hundred and thirteen patients and 58 normal subjects matched by gender, age were enrolled in the study. All the patients had risperidonemonotherapy and undertook a 10-week follow-up. Serum levels of IL-17 and IGF-1 were examined using the enzyme-linked immunosorbent assay and the Positive and Negative Symptoms Scale (PANSS) was applied to estimate the clinical symptoms in patients with schizophrenia. All procedures were repeated at the 10 weeks for patients group.The serum levels of IL-17 and IGF-1 in patients were significantly higher than in normal people. After treatment, IGF-1 levels in patients decreased significantly, whereas the IL-17 serum levels had no significant change compared to their baseline concentration. IGF-1 levels at the baseline were negatively associated with the reduction in negative symptoms score after controlling for age, gender distribution, education, smoking status, and WHR. Additionally, the magnitude of IGF-1 change was negatively correlated with negative symptoms score change after controlling for potential confounding variables. Results suggested that the inflammatory system is activated and serum IGF-1 may contribute to the pathophysiology of the negative symptoms of schizophrenia.

Effects of risperidone on blood levels of interleukin-6 in schizophrenia: A meta-analysis

BACKGROUND

To evaluate the association between risperidone use and interleukin-6 (IL-6) levels by conducting a meta-analysis of controlled before-and-after studies.

METHODS

Studies were identified through a systematic search of PubMed and Embase. The mean and standardized differences were extracted to calculate the standardized mean differences. IL-6 levels were compared in patients with schizophrenia before and after risperidone treatment.

RESULTS

Ten studies were included in the final meta-analysis. The primary findings from our study suggest that there was a significant decrease in serum IL-6 levels after risperidone treatment (P = .021). A subgroup analysis revealed the sources of heterogeneity. The sensitivity analysis indicated that the results were stable, and no publication bias was observed.

CONCLUSIONS

The present meta-analysis provides evidence that risperidone can significantly reduce IL-6 levels in schizophrenia. IL-6 is a potential biomarker of the pathophysiology and clinical processes of schizophrenia.

Cytokine Alterations in Schizophrenia: An Updated Review

Schizophrenia, a multisystem disorder with an unknown etiology, is associated with several immune dysfunctions, including abnormal levels of circulating cytokines. In this review, we investigated the changes of cytokines in schizophrenic patients, their connection with behavioral symptoms severity and their potential clinical implications. We also assessed the possible causative role of abnormal cytokine levels in schizophrenia pathogenesis. Based on meta-analyses, we categorized cytokines according to their changes in schizophrenic patients into four groups: (1) increased cytokines, including interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-1β, IL-12, and transforming growth factor (TGF)-β, (2) non-altered cytokines, including IL-2, IL-4, and IL-17, (3) increased or non-altered cytokines, including IL-8 and interferon (IFN)-γ, and (4) IL-10 with increased, decreased, and non-altered levels. Notably, alterations in cytokines may be variable in four different categories of SP, including first-episode and drug-naïve, first-episode and non-drug-naïve, stable chronic, and chronic in acute relapse. Furthermore, disease duration, symptoms severity, incidence of aggression, and cognitive abilities are correlated with levels of certain cytokines. Clinical implications of investigating the levels of cytokine in schizophrenic patients include early diagnosis, novel therapeutic targets development, patient stratification for choosing the best therapeutic protocol, and predicting the prognosis and treatment response. The levels of IL-6, IL-8, IFN-γ, IL-2 are related to the treatment response. The available evidence shows a potential causative role for cytokines in schizophrenia development. There is a substantial need for studies investigating the levels of cytokines before disease development and delineating the therapeutic implications of the disrupted cytokine levels in schizophrenia.

Effects of olanzapine on cytokine profile and brain-derived neurotrophic factor in drug-naive subjects with first-episode psychosis

Immunological abnormalities have been implicated in schizophrenia. On the other hand, antipsychotics may exert immunomodulatory effects, by triggering pro-inflammatory and anti-inflammatory agents through complex homeostatic mechanisms, which seem to be implicated in medication responsiveness and in the presence or not of adverse effects. There is evidence that olanzapine, a second generation antipsychotic, may increase synapse formation and neurogenesis through alterations in the levels of cytokines and neurotrophic factors. In the present study, we recruited 14 drug-naive inpatients with first-episode schizophrenia (male:female ratio, 7:7) with a mean age of 26.5 years. The positive and negative syndrome scale (PANSS) scores and serum levels of a broad spectrum of cytokines and of brain-derived neurotrophic factor (BDNF) were recorded twice, once at baseline prior to the initiation of olanzapine treatment and 8 weeks later, once the dose of olanzapine had stabilized. Subsequently, the associations between the PANSS scores and the measured markers were examined. Correlation analyses revealed that follow-up PANSS_negative positively correlated with baseline interleukin (IL)-6 (ρ=0.685, P=0.007) and baseline IL-27 levels (ρ=0.785, P=0.001). Furthermore, the percentage change in PANSS_negative [(PANSS-_follow-up - PANSS-_baseline)/PANSS-baseline; ΔPANSS_negative%)] positively correlated with baseline IL-27 (ρ=0.785, P=0.001) and baseline IL-6 levels (ρ=0.685, P=0.007). Finally, linear regression revealed that follow-up PANSS_negative was associated with baseline IL-27 (R²=0.301, P=0.042), ΔPANSS_negative% was associated with baseline IL-6 (R²=0.301, P=0.042) and baseline IL-27 levels (R²=0.446, P=0.009). Thus, these findings indicate that IL-27 and IL-6 may be trait markers in patients being administered olanzapine monotherapy at the onset of schizophrenia. However, further studies are warranted in order to replicate these associations and to confirm their potential use as biomarkers of treatment effectiveness and safety, as well as to explore novel immunomodulatory strategies for the treatment of schizophrenia.

Is psychosis a multisystem disorder? A meta-review of central nervous system, immune, cardiometabolic, and endocrine alterations in first-episode psychosis and perspective on potential models

People with psychotic disorders show abnormalities in several organ systems in addition to the central nervous system (CNS); and this contributes to excess mortality. However, it is unclear how strong the evidence is for alterations in non-CNS systems at the onset of psychosis, how the alterations in non-CNS systems compare to those in the CNS, or how they relate to symptoms. Here, we consider these questions, and suggest potential models to account for findings. We conducted a systematic meta-review to summarize effect sizes for both CNS (focusing on brain structural, neurophysiological, and neurochemical parameters) and non-CNS dysfunction (focusing on immune, cardiometabolic, and hypothalamic-pituitary-adrenal (HPA) systems) in first-episode psychosis (FEP). Relevant meta-analyses were identified in a systematic search of Pubmed and the methodological quality of these was assessed using the AMSTAR checklist (A Measurement Tool to Assess Systematic Reviews). Case-control data were extracted from studies included in these meta-analyses. Random effects meta-analyses were re-run and effect size magnitudes for individual parameters were calculated, as were summary effect sizes for each CNS and non-CNS system. We also grouped studies to obtain overall effect sizes for non-CNS and CNS alterations. Robustness of data for non-CNS and CNS parameters was assessed using Rosenthal's fail-safe N. We next statistically compared summary effect size for overall CNSand overall non-CNS alterations, as well as for each organ system separately. We also examined how non-CNS alterations correlate CNS alterations, and with psychopathological symptoms. Case-control data were extracted for 165 studies comprising a total sample size of 13,440. For people with first episode psychosis compared with healthy controls, we observed alterations in immune parameters (summary effect size: g = 1.19), cardiometabolic parameters (g = 0.23); HPA parameters (g = 0.68); brain structure (g = 0.40); neurophysiology (g = 0.80); and neurochemistry (g = 0.43). Grouping non-CNS organ systems together provided an effect size for overall non-CNS alterations in patients compared with controls (g = 0.58), which was not significantly different from the overall CNS alterations effect size (g = 0.50). However, the summary effect size for immune alterations was significantly greater than that for brain structural (P < 0.001) and neurochemical alterations (P < 0.001), while the summary effect size for cardiometabolic alterations was significantly lower than neurochemical (P = 0.04), neurophysiological (P < 0.001), and brain structural alterations (P = 0.001). The summary effect size for HPA alterations was not significantly different from brain structural (P = 0.14), neurophysiological (P = 0.54), or neurochemical alterations (P = 0.22). These outcomes remained similar in antipsychotic naive sensitivity analyses. We found some, but limited and inconsistent, evidence that non-CNS alterations were associated with CNS changes and symptoms in first episode psychosis. Our findings indicate that there are robust alterations in non-CNS systems in psychosis, and that these are broadly similar in magnitude to a range of CNS alterations. We consider models that could account for these findings and discuss implications for future research and treatment.

Kinetics of Cytokine Levels during Antipsychotic Treatment in Schizophrenia: A Meta-Analysis

BACKGROUND

Immune system dysfunction is a hypothesis in the psychopathology of schizophrenia, but the impact of antipsychotic treatment within this system is not clear. The aim of this meta-analysis was to investigate the impact of antipsychotic treatment on cytokine levels in in vivo studies on schizophrenia.

METHODS

After a systematic database search, original data were extracted with the help of certain authors. Means and SDs were extracted to calculate standardized mean differences. Cytokine levels were compared in vivo in schizophrenia patients, before and after antipsychotic treatment. Meta-regressions were performed to explore the influence of demographic and clinical variables on cytokine level standardized mean differences. Stratifications by treatment and diagnosis were also performed.

RESULTS

Forty-seven studies were included in this meta-analysis. Proinflammatory cytokine level decreases were found for interleukin-1 β levels (P<.0001) and interferon-γ (P=.01) and a statistical trend towards a decrease in interleukin-6 (P=.08) and tumor necrosis factor-α (P=.07) levels. An antiinflammatory cytokine level increase was found for soluble tumor necrosis factor-R2 (P<.001) and soluble interleukin 2-R (P=.03) levels. A meta-regression analysis found a correlation between interleukin-6 level standardized mean differences and positive schizophrenia symptom score standardized mean differences before and after treatment (P=.01). Stratification by diagnosis or treatment found a possible impact of the kinetics of cytokine levels.

CONCLUSIONS

The present meta-analysis provides evidence that antipsychotic treatment has an antiinflammatory effect and could normalize immune balance dysfunction in schizophrenia. Interleukin-6 level normalization could be a marker of illness equilibration and thus used in clinical practice.

Decreased IL-1ra and NCAM-1/CD56 Serum Levels in Unmedicated Patients with Schizophrenia Before and After Antipsychotic Treatment

OBJECTIVE

Schizophrenia (SZ) has been associated with the inflammatory-related and immunological pathogenesis. This study investigates the aberration of cytokines in patients with SZ.

METHODS

Thirty patients with SZ without antipsychotic treatment for at least two weeks participated. We measured the serum levels of fourteen cytokines at hospital admission and after 8-week antipsychotic treatment. Severity was measured by expanded version of 24-items brief psychiatric rating scale (BPRS-E). Repeated measure analyses of variance were conducted.

RESULTS

The interleukin-1 receptor antagonist (IL-1ra) was significantly decreased after 8-week antipsychotic treatment than those of before antipsychotic treatment (F=12.15, df=1/30, p=0.002). Neural cell adhesion molecule 1/CD56 (NCAM-1/CD56) was significantly decreased (F=6.61, df=1/30, p=0.016) among those with second-generation antipsychotics but not first-generation antipsychotics treatment. The changes of BPRS-E-manic and BPRS-E-anxiety scores correlated with the baseline IL-1ra (r=-0.393), IL-6 (r=-0.407), and insulin like growth factor binding protein 3 (r=-0.446). Additionally, the changes of BPRS-E and BPRS-E-negative scores correlated with the changes of brain-derived neurotrophic factor (r=0.372) and interferon-gamma (r=0.375).

CONCLUSION

Our study supports that IL-1ra and NCAM-1/CD56 may be considered as markers of developing SZ.

Inflammation, substance use, psychopathology, and cognition in phase 1 of the clinical antipsychotic trials of intervention effectiveness study

INTRODUCTION

Schizophrenia has been associated with aberrant blood levels of inflammatory markers. However, patients with comorbid illicit drug use have been inadequately studied with respect to immune function. Furthermore, associations between inflammatory markers, psychopathology, and cognition have been inconsistently considered. We investigated relationships between inflammatory markers, comorbid marijuana and cocaine use, and psychopathology and cognition in patients with schizophrenia.

METHOD

For subjects with available fasting data from the baseline visit of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) schizophrenia trial, inflammatory markers were investigated as predictors of psychopathology and cognition in patients with and without comorbid marijuana or cocaine use, using linear regression models controlling for potential confounding factors.

RESULTS

Compared to subjects with a negative urine drug screen (UDS), marijuana use was a predictor of higher lymphocytes and E-selectin, and lower leptin (p≤0.04 for each); cocaine use was a predictor of higher adiponectin (p=0.04). In subjects with marijuana use, lower WBC and higher IL-6 were predictors of higher PANSS total score (p<0.05 for each). In subjects with cocaine use, lower total and differential WBC were predictors of higher PANSS total score (p<0.04 for each). In younger, non-obese subjects with a negative UDS, higher monocytes and IL-6 were predictors of PANSS total score (p<0.04 for each).

CONCLUSIONS

Our findings provide additional evidence that inflammation may be associated with psychopathology and cognition in some patients with schizophrenia. Furthermore, there is preliminary evidence for differential effects of comorbid marijuana and cocaine use on these relationships.

A pilot study on immuno-psychiatry in the 22q11.2 deletion syndrome: A role for Th17 cells in psychosis?

BACKGROUND

A growing body of evidence supports a role for immune alterations in Schizophrenia Spectrum Disorders (SSD). A high prevalence (25-40%) of SSD has been found in patients with 22q11.2 deletion syndrome (22q11.2DS), which is known for T-cell deficits due to thymus hypoplasia. This study is the first to explore the association between the T-cell subsets and psychotic symptoms in adults with 22q11.2DS.

METHODS

34 individuals (aged 19-38 yrs.) with 22q11.2DS and 34 healthy age- and gender matched control individuals were included. FACS analysis of the blood samples was performed to define T-cell subsets. Ultra-high risk for psychosis or diagnosis of SSD was determined based on CAARMS interviews and DSM-5 criteria for SSD. Positive psychotic symptom severity was measured based on the PANSS positive symptoms subscale.

RESULTS

A partial T-cell immune deficiency in 22q11.2DS patients was confirmed by significantly reduced percentages of circulating T and T-helper cells. Significantly higher percentages of inflammatory Th1, Th17, and memory T-helper cells were found in adults with 22q11.2DS. Most importantly an increased Th17 percentage was found in adults with psychotic symptoms as compared to non-psychotic adults with 22q11.2DS, and Th17 percentage were related to the presence of positive psychotic symptoms.

CONCLUSIONS

Given the literature on the role of T cells and in particular of Th17 cells and IL-17 in hippocampus development, cognition and behavior, these results support the hypothesis for a role of Th17 cells in the development and/or regulation of psychotic symptoms in 22q11.2DS. This pilot study underlines the importance to further study the role of T-cell defects and of Th17 cells in the development of psychiatric symptoms. It also supports the possibility to use 22q11.2DS as a model to study T-cell involvement in the development of SSD.

Interplay of Brain-Derived Neurotrophic Factor and Cytokines in Schizophrenia

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family and plays an important role in neuroplasticity, differentiation and survival of neurons, as well as their function. Neuroinflammation has been explored in the pathophysiology of many mental disorders, such as schizophrenia. Cytokines representing different types of immune responses have an impact on neurogenesis and BDNF expression. Cross-regulation of BDNF and cytokines is accomplished through several signalling pathways. Also, typical and atypical antipsychotic drugs variously modulate the expression of BDNF and serum levels of cytokines, which can possibly be used in evaluation of therapy effectiveness. Comorbidity of metabolic syndrome and atopic diseases has been considered in the context of BDNF and cytokines interplay in schizophrenia.

Interleukin-6 in Schizophrenia-Is There a Therapeutic Relevance?

Renewing interest in immune aspects of schizophrenia and new findings about the brain-fat axis encourage us to discuss the possible role of interleukin-6 (IL-6) in schizophrenia. Previously, it was suggested that a primary alteration of the innate immune system may be relevant in schizophrenia. Functional dichotomy of IL-6 suggests that this chemical messenger may be responsible for regulating the balance between pro- and anti-inflammatory responses, with tissue-specific properties at the periphery and in the central nervous system. Specific phase of this chronic and deteriorating disorder must be considered, which can involve IL-6 in acute or possible chronic inflammation and/or autoimmunity. We give an overview of IL-6 role in the onset and progression of this disorder, also considering cognitive impairment and metabolic changes in patients with schizophrenia. Data suggest that decreased serum level of IL-6 following antipsychotic therapy could be predisposing factor for the development of obesity and obesity-related metabolic disorders in schizophrenia. As we reviewed, the IL-6 plays significant role in disease genesis and progression, so the use of specific inhibitors may not only be beneficial for exacerbation and alleviation of positive symptoms, but may attenuate cognitive impairment in patients with schizophrenia.

An exploratory study of immune markers in acute and transient psychosis

The aim of this study was to look into the balance of pro-inflammatory (TNF-α, IL-6) and anti-inflammatory (TGF-β) cytokines and their association with stress, alterations in HPA axis activity and the disease severity in acute psychosis. Socio-demographic and clinical details were collected from 41 in-patients with a diagnosis of Acute and Transient Psychotic Disorder. Holmes and Rahe Stress Scale for stress in the preceding year, and Brief Psychiatric Rating Scale at baseline and follow up (4-12 weeks) for psychopathology were applied. IL-6, TNF-α (pro-inflammatory), TGF-β (anti-inflammatory) and Cortisol (morning and afternoon values) were measured at baseline and follow up. A total of 30 out of 41 cases recruited had follow up data available. The levels of IL-6 (p<0.001), TNF-α (p<0.001) and TGF-β (p<0.001) at baseline were all found to be significantly elevated compared to 42 age and gender matched healthy controls. There was a significant increase in the levels of TNF-α (p=0.020) and morning levels of cortisol (p=0.009) and a significant decrease in the levels of TGF-β (p=0.004) and afternoon levels of cortisol (p=0.043) from baseline to follow up. This study showed that there was an increased level of both pro and anti-inflammatory cytokines at baseline and a prolonged pro - inflammatory compared to anti - inflammatory response which warrants larger prospective studies and comparative studies to patients with schizophrenia and bipolar disorders.

A meta-analysis of blood cytokine network alterations in psychiatric patients: comparisons between schizophrenia, bipolar disorder and depression

Schizophrenia, bipolar disorder and major depressive disorder (MDD) have all been associated with aberrant blood cytokine levels; however, neither the pattern of cytokine alterations nor the impact of clinical status have been compared across disorders. We performed a meta-analysis of blood cytokines in acutely and chronically ill patients with these major psychiatric disorders. Articles were identified by searching the PubMed, PsycInfo and Web of Science, and the reference lists of these studies. Sixty-eight studies met the inclusion criteria (40 schizophrenia, 10 bipolar disorder and 18 MDD) for acutely ill patients. Forty-six studies met the inclusion criteria (18 schizophrenia, 16 bipolar disorder and 12 MDD) for chronically ill patients. Levels of two cytokines (interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α)), one soluble cytokine receptor (sIL-2R), and one cytokine receptor antagonist (IL-1RA) were significantly increased in acutely ill patients with schizophrenia, bipolar mania and MDD compared with controls (P<0.01). Following treatment of the acute illness, IL-6 levels significantly decreased in both schizophrenia and MDD (P<0.01); sIL-2R levels increased in schizophrenia; and IL-1RA levels in bipolar mania decreased. In chronically ill patients, the levels of IL-6 were significantly increased in schizophrenia, euthymic (but not depressed) bipolar disorder and MDD compared with controls (P<0.01). The levels of IL-1β and sIL-2R were significantly increased in both chronic schizophrenia and euthymic bipolar disorder. Overall, there were similarities in the pattern of cytokine alterations in schizophrenia, bipolar disorder and MDD during acute and chronic phases of illness, raising the possibility of common underlying pathways for immune dysfunction. Effects of treatment on cytokines were more robust for schizophrenia and MDD, but were more frequently studied than for acute mania. These findings have important implications for our understanding of the pathophysiology and treatment of major psychiatric disorders.

Family-based association study of interleukin 10 (IL10) and interleukin 10 receptor alpha (IL10RA) functional polymorphisms in schizophrenia in Polish population

Schizophrenia is a heterogeneous disorder and its etiology remains incompletely elucidated. Among possible causes, immunological factors have been implicated in its pathogenesis and course. Interleukin-10 (IL10) and it's receptor IL10RA may play an important role for immunological aspects in etiologies of major psychiatric disorders including schizophrenia. The aim of this study was to perform a transmission disequilibrium test (TDT) on a group of 146 schizophrenia trios from the Polish population. Functional polymorphisms from IL10 (rs1800872, rs1800871, rs1800896, rs1800890, and rs6676671) and IL10RA (rs3135932 and rs2229113) genes were analyzed. A lack of association with schizophrenia was detected for IL10 and IL10RA single polymorphisms and haplotypes.

High predictive value of immune-inflammatory biomarkers for schizophrenia diagnosis and association with treatment resistance

OBJECTIVES

Recent schizophrenia (SCZ) research aims to establish biomarkers with high predictive value for the diagnosis, severity of illness or treatment resistance. SCZ is accompanied by activated immune-inflammatory pathways, including increased levels of cytokines and chemokines, but few studies tried to identify predictive properties of such measures.

METHODS

We included 54 medicated SCZ patients and 118 healthy controls and examined 15 cytokines and chemokines. Possible associations between these immune-inflammatory biomarkers and the diagnosis of SCZ, severity of illness and treatment resistance were investigated.

RESULTS

SCZ is associated with a specific cytokine - chemokine profile, i.e., increased CCL11, MIP-1α, sTNF-R1 and sTNF-R2 levels, and decreased levels of IP-10, TNF-α, IL-2 and IL-4. The combination of five biomarkers (sTNF-R1, sTNF-R2, CCL11, IP-10, IL-4) may predict the diagnosis of SCZ with a sensitivity of 70.0% and a specificity of 89.4%. There was a weak association between the negative symptoms and biomarkers, i.e., IL-2 (inversely) and CCL11 (positively). Patients with treatment resistance showed increased levels of sTNF-R1, sTNF-R2 and MCP-1.

CONCLUSIONS

The findings of this study reinforce that SCZ is associated with a pro-inflammatory profile and suggest that some immune mediators may be used as reliable biomarkers for the diagnosis of SCZ and treatment resistance.

Adaptive Immunity in Schizophrenia: Functional Implications of T Cells in the Etiology, Course and Treatment

Schizophrenia is a severe and highly complex neurodevelopmental disorder with an unknown etiopathology. Recently, immunopathogenesis has emerged as one of the most compelling etiological models of schizophrenia. Over the past few years considerable research has been devoted to the role of innate immune responses in schizophrenia. The findings of such studies have helped to conceptualize schizophrenia as a chronic low-grade inflammatory disorder. Although the contribution of adaptive immune responses has also been emphasized, however, the precise role of T cells in the underlying neurobiological pathways of schizophrenia is yet to be ascertained comprehensively. T cells have the ability to infiltrate brain and mediate neuro-immune cross-talk. Conversely, the central nervous system and the neurotransmitters are capable of regulating the immune system. Neurotransmitter like dopamine, implicated widely in schizophrenia risk and progression can modulate the proliferation, trafficking and functions of T cells. Within brain, T cells activate microglia, induce production of pro-inflammatory cytokines as well as reactive oxygen species and subsequently lead to neuroinflammation. Importantly, such processes contribute to neuronal injury/death and are gradually being implicated as mediators of neuroprogressive changes in schizophrenia. Antipsychotic drugs, commonly used to treat schizophrenia are also known to affect adaptive immune system; interfere with the differentiation and functions of T cells. This understanding suggests a pivotal role of T cells in the etiology, course and treatment of schizophrenia and forms the basis of this review.

The potential of immune biomarkers to advance personalized medicine approaches for schizophrenia

Molecular profiling studies have helped increase the understanding of the immune processes thought to be involved in the etiology and pathophysiology of psychiatric disorders such as schizophrenia. Current therapeutic interventions with first- and second-generation antipsychotics are suboptimal. Poor response rates and debilitating side effects often lead to poor treatment compliance. This highlights the pressing need to identify more effective treatments as well as objective biomarker based tests, which can help predict treatment response and identify diagnostic subpopulations. Such tests could enable early detection of patients who will benefit from particular therapeutic interventions. In this review, we discuss studies relating to dysfunctions of the immune system in patients with schizophrenia and the effects of antipsychotic medication on the molecular components of these systems. Immune system dysfunction may in part be related to genetic risk factors for schizophrenia, but there is substantial evidence that a wide range of environmental factors ranging from exposure to infectious agents such as influenza and Toxoplasma gondii to HPA axis dysfunction play an important role in the etiopathogenesis of schizophrenia. Ongoing research efforts, testing therapeutic efficacy of anti-inflammatory agents used as add-on medications are also discussed. From a therapeutic perspective, these represent the initial steps toward novel treatment approaches and more effective patient care in the field of mental health.

Regulation of interleukin-6 and leptin in schizophrenia patients: a preliminary analysis

Objective

Immune-inflammatory mediators play a pivotal role in brain signaling and have been increasingly associated with the pathophysiology of schizophrenia. Many studies have indicated an increased level of immune-inflammatory interleukin-6 (IL-6) in schizophrenia. IL-6 is a well-known chief stimulator of inflammation. Of late leptin has also been implicated in the inflammatory pathway of schizophrenia. In this study we measured and compared serum levels of IL-6 and leptin in patients with schizophrenia to healthy controls, and investigated the relationship between IL-6 and leptin.

Methods

Serum IL-6 and leptin were determined in 20 patients diagnosed with schizophrenia and in 19 healthy controls matched by gender, age and body mass index (BMI) using commercial Bioplex assays.

Results

Using Mann-Whitney U-test, significantly increased IL-6 levels were found in the patients but there was no significant difference in leptin levels though a trend towards higher leptin was observed in the patients. Spearman correlations did not show any correlation between IL-6 and clinical variables except antipsychotic dosage. Leptin significantly correlated with gender and BMI. A large effect size correlation was observed between IL-6 and leptin in the patients but not in the controls. Multiple regression analysis performed on patients, after adjusting for gender and BMI, revealed there was no significant association between IL-6 and leptin.

Conclusion

IL-6 and leptin levels may reflect the chronic inflammatory state associated with schizophrenia but further evaluation is required. Also, it is important to consider the confounding effects of obesity in any examination of relationships between groups with regard to cytokines and adipokines.

Activation of Th17 cells in drug naïve, first episode schizophrenia

OBJECTIVE

The present study was to examine the role of pro-inflammatory T helper 17 (Th17) cells in drug naïve, first episode schizophrenia.

METHOD

Patients with normal weight, drug naïve, first episode schizophrenia and healthy controls were enrolled in the study. Flow cytometric analysis was performed to analyze the proportion of Th17 cells among the CD4(+) T cells. Plasma levels of interleukin-17 (IL-17), interferon-γ (IFN-γ) and interleukin-6 (IL-6) were examined using enzyme-linked immunosorbent assay (ELISA). Psychopathology was assessed using the Positive and Negative Syndrome Scale (PANSS). All measures were repeated for the patient group after 4 weeks of risperidone treatment.

RESULTS

Sixty-nine patients with normal weight, drug naïve, first episode schizophrenia and 60 healthy controls were enrolled. At baseline, the patient group hadz significantly higher proportions of Th17 cells and plasma levels of IFN-γ and IL-6 compared with the control group (p's<0.01). Within the patient group, there were significant positive relationships between the proportion of Th17 cells, plasma levels of IL-17, IFN-γ, IL-6 and the PANSS total score after controlling for potential confounding variables (p's<0.05). After 4weeks of risperidone treatment, the proportion of Th17 cells decreased significantly (p <0.001), and there was a significant positive relationship between the PANSS total score change rate and the change in proportion of Th17 cells (p = 0.039).

CONCLUSIONS

Patients with normal weight, drug naïve, first episode schizophrenia present activation of Th17 cells, which might be associated with therapeutic response after risperidone treatment.

Peripheral interleukin-2 level is associated with negative symptoms and cognitive performance in schizophrenia

Although several studies have pointed to a possible role of interleukin 2 (IL-2) in schizophrenia (SZ), association between IL-2 and the different groups of symptoms has not been explored. The objective of this study was to investigate a possible correlation of peripheral IL-2 levels with symptoms and cognitive performance in patients with SZ. In addition, we compared the plasma levels of IL-2 between patients with SZ and healthy controls. Twenty-nine chronically medicated outpatients with SZ according to DSM-IV were compared with twenty-six healthy controls. The patients were evaluated with the Positive and Negative Syndrome Scale (PANSS), the Calgary Depression Scale for Schizophrenia (CDSS), the Clinical Global Impression (CGI) and the Global Assessment of Functioning (GAF). All the participants had blood collected into EDTA tubes by venipuncture between 9:00 and 10:00AM. Plasma concentrations of IL-2 were determined by cytometric bead array. A computerized neuropsychological battery assessed verbal learning, verbal fluency, working memory, set shifting, executive function, inhibition and intelligence. Patients with SZ had lower levels of IL-2 than healthy controls (p<0.001). In the SZ group, IL-2 levels were positively correlated with scores in the digit span test (rho=0.416, P=0.025) and intelligence (rho=0.464, P=0.011). We also found a negative correlation between IL-2 and total score in the negative subscale of PANSS (rho=-0.447, p=0.015). Our findings suggest that IL-2 may be involved in the mechanisms related to cognitive deterioration and negative symptomatology in schizophrenia.

Antipsychotics' effects on blood levels of cytokines in schizophrenia: a meta-analysis

OBJECTIVES

Evidence-based medicine suggests that schizophrenia is associated with an inflammatory syndrome, but the extent to which this syndrome is normalized by antipsychotic treatment has yet to be determined.

METHODS

A systematic quantitative review of the effects of antipsychotics on peripheral cytokine levels in schizophrenia was performed, using follow-up studies providing in vivo cytokine assessments before and after treatment.

RESULTS

We retrieved 23 studies (total of 762 subjects) which showed that antipsychotic treatment significantly increases plasma levels of soluble interleukin-2 receptor and reduces the plasma levels of interleukin-1β and interferon-γ.

CONCLUSIONS

These results show that antipsychotics produce anti-inflammatory effects in schizophrenia.

Elevated levels of adiponectin and other cytokines in drug naïve, first episode schizophrenia patients with normal weight

OBJECTIVE

The study was to examine the levels of adiponectin (APN) and other cytokines, and body metabolism in drug naïve, first episode schizophrenia patients with normal weight.

METHODS

Ninety-six drug naïve, first episode schizophrenia patients with normal weight (SZ group), 60 healthy individuals with normal weight (control group), and 60 overweight or obese but otherwise healthy individuals (obesity group) were enrolled in the study. Serum levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and APN were measured using enzyme linked immunosorbent assay (ELISA). Glucose oxidase was used to measure plasma glucose level. Lipid levels were measured using the enzymatic colorimetric method.

RESULTS

Serum levels of IL-1β, IL-6 and TNF-α in both the SZ group and the obesity group were significantly higher than those in the control group (p's<0.001). There were no significant differences between the SZ group and the obesity group on those cytokines (p's>0.05). In addition, the levels of APN were significantly higher in the SZ group (p<0.001), and significantly lower in the obesity group (p<0.01) compared with the control group. Further, there were significant positive relationships between levels of APN and levels of other cytokines within the SZ group (p's<0.05); in contrast, there were significant negative relationships between levels of APN and levels of other cytokines within the obesity group (p's<0.05). Fasting serum levels of glucose, LDL, triglycerides and total cholesterol were significantly higher, and fasting serum levels of HDL were significantly lower in the obesity group compared with the other two groups (p's<0.01). There were no significant differences in any of the metabolic parameters between the control group and the SZ group (p's>0.05).

CONCLUSIONS

Drug naïve, first episode schizophrenia patients with normal weight seem to present an up-regulated inflammatory status as reflected by elevated levels of IL-1β, IL-6, and TNF-α. APN may play a unique pro-inflammatory role in this patient population. Implications of the findings in relation to the pathogenesis of schizophrenia and the vulnerability for metabolic problems were discussed.

Genetic variants in transforming growth factor-β gene (TGFB1) affect susceptibility to schizophrenia

Immense body of evidence indicates that dysfunction of immune system is implicated in the etiology of schizophrenia. The immune theory of schizophrenia is supported by alterations in cytokine profile in the brain and peripheral blood. Given the strong genetic background of schizophrenia, it might be assumed that aberrant production of cytokines might be the consequence of genetic factors. This study aimed at investigating the association between schizophrenia susceptibility and selected functional polymorphisms in genes encoding cytokines including: interleukin-2 (IL2 −330T>G, rs2069756), interleukin-6 (IL-6 −174G>C, rs1800795), interferon-γ (IFNG +874T>A, rs2430561) as well as for the first time transforming growth factor-β1 (TGFB1 +869T>C, rs1800470 and +916G>C, rs1800471). We recruited 151 subjects with schizophrenia and 279 controls. There was a significant difference in the genotype distribution and allelic frequency of the TGFB1 +869T>C between patients with schizophrenia and healthy controls (p < 0.05). The risk of schizophrenia was more than two-fold higher in carriers of T allele (CT+TT genotypes) than individuals with CC genotype. Given documented gender differences in incidence of schizophrenia, we conducted separate analyses of male and female participants. We have shown that the association was significant in females, while in males it reached a trend toward statistical significance. To the best of our knowledge, it is the first report showing the association between TGFB1 +869T>C polymorphism and schizophrenia.

Antipsychotics can modulate the cytokine profile in schizophrenia: attenuation of the type-2 inflammatory response

OBJECTIVE

We recently reported that the type-2 cytokine response is increased in schizophrenia. The aim of this study was to analyse the effects of antipsychotic drugs on the serum levels of type-1 (TNF-α, IFN-γ), type-2 (IL-4, IL-10), type-17 (IL-17) and regulatory cytokines (TGF-β, IL-27 and IL-6).

METHODS

Cytokine measurements in the patients were performed on day 0 and day 30 of the treatment using standard ELISA assays. Three groups of subjects were studied: patients that were unmedicated with First Episode Psychosis (FEP; n=88), patients that were treated with antipsychotics with Schizophrenia in relapse (SC in relapse; n=45) and healthy controls (n=36).

RESULTS

TGF-β levels were increased in both patient groups and were further enhanced after treatment in the FEP group (p=0.014) but not in the SC relapse group. Antipsychotic treatment was correlated with lower levels of IL-4, IL-6 and IL-27 (p<0.005) in the FEP group. Finally, the serum levels of IL-17 were not significantly altered between the two measurements but were significantly lower in the FEP group (p<0.001) when compared with healthy controls. After therapy, patients with SC who were in relapse had decreased serum levels of IL-4 (p=0.006) and IL-6 (p=0.007). We also observed a weak negative correlation between the IFN-γ/TGF-β ratio and the total PANSS score and between the IL-17/TGF-β ratio and the negative and general psychopathology subscales.

CONCLUSION

The increased type-2 cytokine serum levels in schizophrenia appear to be downregulated by antipsychotic treatment.

Is T-helper type 2 shift schizophrenia-specific? Primary results from a comparison of related psychiatric disorders and healthy controls

AIM

An imbalance between T-helper type 1 (Th1) and type 2 (Th2) cytokines has been implicated in schizophrenia, although empirical evidence is rare. The aim of this study was to examine if a Th1/Th2 imbalance occurs in schizophrenia and schizophrenia-related disorder.

METHODS

Twenty-six subjects with schizophrenia, 26 subjects with schizophrenia-related disorders, and 26 healthy controls were recruited. The Human Th1/Th2 Cytokine Cytometric Bead Array Kit-II was utilized to assess serum Th1/Th2 cytokines and ratios simultaneously. MANOVA was used to detect differences among the three diagnostic groups in distinct Th1/Th2 cytokines/ratios. Pearson/Spearman correlations were used to examine the relationships between distinct Th1/Th2 cytokines/ratios and clinical/psychopathological data in schizophrenia.

RESULTS

Interferon (IFN)-γ/interleukin (IL)-4, IFN-γ/IL-10, IL-2/IL-4, and tumor necrosis factor (TNF)-α/IL-4 ratios were significantly decreased in schizophrenia, but not in schizophrenia-related disorders compared to healthy controls. IFN-γ/IL-4 and IFN-γ/IL-10 in schizophrenia subjects positively correlated with age, but not in schizophrenia-related disorder subjects or in healthy controls.

CONCLUSION

A clear Th2 shift was observed in schizophrenia, but not in schizophrenia-related disorders. The Th2 shift in schizophrenia appeared to be an aberrant developmental phenomenon.

Putative neuroprotective agents in neuropsychiatric disorders

In many individuals with major neuropsychiatric disorders including depression, bipolar disorder and schizophrenia, their disease characteristics are consistent with a neuroprogressive illness. This includes progressive structural brain changes, cognitive and functional decline, poorer treatment response and an increasing vulnerability to relapse with chronicity. The underlying molecular mechanisms of neuroprogression are thought to include neurotrophins and regulation of neurogenesis and apoptosis, neurotransmitters, inflammatory, oxidative and nitrosative stress, mitochondrial dysfunction, cortisol and the hypothalamic-pituitary-adrenal axis, and epigenetic influences. Knowledge of the involvement of each of these pathways implies that specific agents that act on some or multiple of these pathways may thus block this cascade and have neuroprotective properties. This paper reviews the potential of the most promising of these agents, including lithium and other known psychotropics, aspirin, minocycline, statins, N-acetylcysteine, leptin and melatonin. These agents are putative neuroprotective agents for schizophrenia and mood disorders.

Schizophrenia: linking prenatal infection to cytokines, the tryptophan catabolite (TRYCAT) pathway, NMDA receptor hypofunction, neurodevelopment and neuroprogression

In 1995, the macrophage-T lymphocyte theory of schizophrenia (Smith and Maes, 1995) considered that activated immuno-inflammatory pathways may account for the higher neurodevelopmental pathology linked with gestational infections through the detrimental effects of activated microglia, oxidative and nitrosative stress (O&NS), cytokine-induced activation of the tryptophan catabolite (TRYCAT) pathway and consequent modulation of the N-methyl d-aspartate receptor (NMDAr) and glutamate production. The aim of the present paper is to review the current state-of-the art regarding the role of the above pathways in schizophrenia. Accumulating data suggest a powerful role for prenatal infection, both viral and microbial, in driving an early developmental etiology to schizophrenia. Models of prenatal rodent infection show maintained activation of immuno-inflammatory pathways coupled to increased microglia activation. The ensuing activation of immuno-inflammatory pathways in schizophrenia may activate the TRYCAT pathway, including increased kynurenic acid (KA) and neurotoxic TRYCATs. Increased KA, via the inhibition of the α7 nicotinic acetylcholine receptor, lowers gamma-amino-butyric-acid (GABA)ergic post-synaptic current, contributing to dysregulated glutamatergic activity. Hypofunctioning of the NMDAr on GABAergic interneurons will contribute to glutamatergic dysregulation. Many susceptibility genes for schizophrenia are predominantly expressed in early development and will interact with these early developmental driven changes in the immuno-inflammatory and TRYCAT pathways. Maternal infection and subsequent immuno-inflammatory responses are additionally associated with O&NS, including lowered antioxidants such as glutathione. This will contribute to alterations in neurogenesis and myelination. In such a scenario a) a genetic or epigenetic potentiation of immuno-inflammatory pathways may constitute a double hit on their own, stimulating wider immuno-inflammatory responses and thus potentiating the TRYCAT pathway and subsequent NMDAr dysfunction and neuroprogression; and b) antipsychotic-induced changes in immuno-inflammatory, TRYCAT and O&NS pathways would modulate the CNS glia-neuronal interactions that determine synaptic plasticity as well as myelin generation and maintenance.

The metabolic syndrome in schizophrenia: is inflammation a contributing cause?

This non-systematic review of the literature summarizes the evidence that inflammation plays a major role in the psychopathology of schizophrenia and in the mechanisms that contribute to physical ill health that is commonly associated with schizophrenia. The impact of prenatal infections on the developing brain, the possible genetic link between the human lymphocyte antigen gene, inflammation, heart disease and diabetes, together with the increase in pro-inflammatory cytokines in the blood and cerebrospinal fluid provide convincing evidence that inflammation is a major factor in the pathology of this disorder. The changes in immune-related markers and specific neurotransmitters associated with the positive symptoms of schizophrenia are described. In addition, the possible mechanism whereby structural changes occur in the brain is associated with the neurotoxic effects of pro-inflammatory cytokines, together with the neurotoxic metabolites from the tryptophan-kynurenine pathway that is activated by pro-inflammatory cytokines, is also discussed. The role of effective antipsychotic drug treatment in attenuating the inflammatory response is described. However, evidence is limited regarding the causal connection between atypical antipsychotic drugs and the changes in glucose and lipid metabolism that could trigger the onset of physical ill health, including diabetes and heart disease. Indeed, there is evidence that there is a metabolic predisposition to diabetes in patients with schizophrenia that is exacerbated by obesity and thereby contributes to cardiovascular disease and other co-morbid illnesses. It is concluded that the effects of inflammatory mediators on the brain causally contribute to the pathology of schizophrenia and the ill health that accompanies the disorder.

Reversal of imbalance between kynurenic acid and 3-hydroxykynurenine by antipsychotics in medication-naïve and medication-free schizophrenic patients

The association between the pro-inflammatory state of schizophrenia and increased tryptophan degradation into kynurenine has been reported. However, the relationship between metabolites from subdivisions of the kynurenine pathway, kynurenic acid and 3-hydroxykynurenine, remains unknown. The present study tested the relationship between these kynurenine metabolites in the plasma of medication-naïve (n=35) or medication-free (n=18) patients with schizophrenia at admission and following 6-week antipsychotic treatment compared to healthy controls (n=48). The plasma concentrations of kynurenic acid (nmol/l) were lower (difference=-8.44 (-13.22 to -3.65); p=0.001) and of 3-hydroxykynurenine (nmol/l) were higher (difference=11.24 (8.11-14.37); p<0.001) in the patients compared with the healthy controls. The kynurenic acid/kynurenine (difference=-2.75 (-5.115 to -0.336); p=0.026) and kynurenic acid/3-hydroxykynurenine (difference=-1.08 (-1.431 to -0.729); p<0.001) ratios were also lower in the patients. After the 6-week treatment, the patients' plasma kynurenic acid levels (difference=3.85 (-0.23 to 7.94); p=0.064) showed a trend towards an increase, whereas plasma 3-hydroxykynurenine levels (difference=22.41 (19.76-25.07); p<0.001) decreased. As a consequence, the kynurenic acid/3-hydroxykynurenine ratio (difference=-4.41 (-5.51 to -3.3); p<0.001) increased. Higher initial plasma kynurenic acid levels on admission or increased kynurenic acid/kynurenine ratio after treatment were associated with reduction of clinical symptoms scores upon discharge although higher kynurenic acid/kynurenine on admission may induce higher positive symptoms score. In contrast, higher 3-hydroxykynurenine is associated with lower positive symptoms score. These results indicate that there is an imbalance in the kynurenine pathway in schizophrenia. The 6-week antipsychotic treatment may partially reverse the imbalance in kynurenine metabolism and that in turn induces clinical response.

Meta-analysis of cytokine alterations in schizophrenia: clinical status and antipsychotic effects

BACKGROUND

Schizophrenia is associated with immune system dysfunction, including aberrant cytokine levels. We performed a meta-analysis of these associations, considering effects of clinical status and antipsychotic treatment following an acute illness exacerbation.

METHODS

We identified articles by searching PubMed, PsychInfo, and Institute for Scientific Information and the reference lists of identified studies.

RESULTS

Forty studies met the inclusion criteria. Effect sizes were similar for studies of acutely relapsed inpatients (AR) and first-episode psychosis (FEP). Interleukin (IL)-1β, IL-6, and transforming growth factor-β (TGF-β) appeared to be state markers, as they were increased in AR and FEP (p < .001 for each) and normalized with antipsychotic treatment (p < .001, p = .008, and p = .005, respectively). In contrast, IL-12, interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and soluble IL-2 receptor (sIL-2R) appeared to be trait markers, as levels remained elevated in acute exacerbations and following antipsychotic treatment. There was no difference in IL-6 levels between stable medicated outpatients and control subjects (p = .69). In the cerebrospinal fluid, IL-1β was significantly decreased in schizophrenia versus controls (p = .01).

CONCLUSIONS

Similar effect sizes in AR and FEP suggest that the association between cytokine abnormalities and acute exacerbations of schizophrenia is independent of antipsychotic medications. While some cytokines (IL-1β, IL-6, and TGF-β) may be state markers for acute exacerbations, others (IL-12, IFN-γ, TNF-α, and sIL-2R) may be trait markers. Although these results could provide the basis for future hypothesis testing, most studies did not control for potential confounding factors such as body mass index and smoking.

Understanding the role of inflammatory-related pathways in the pathophysiology and treatment of psychiatric disorders: evidence from human peripheral studies and CNS studies

Many lines of evidence now support the hypothesis that inflammation-related pathways are involved in the pathophysiology of psychiatric disorders. Much of the data underpinning this hypothesis has come from the study of inflammation-related proteins in blood of individuals with mood disorders and schizophrenia. Significantly, recent data have emerged to suggest that changes in inflammation-related pathways are present in the CNS of subjects with psychiatric disorders. It is therefore timely to overview how such data, plus data on the role of inflammation-related proteins in CNS function, is contributing to understanding the pathophysiology of mood disorders and schizophrenia. In addition, it has been suggested that antidepressants, mood stabilizers and antipsychotic drugs act on inflammation-related pathways and therefore measuring levels of inflammation-related proteins in blood may be useful in monitoring treatment responsiveness. Despite these important neuropsychopharmacological discoveries, there is no clear understanding as to how inflammatory-related pathways can precipitate the onset of psychiatric symptoms. This review will focus on data suggesting that acute-reactive proteins and cytokines are affected by the pathophysiology of mood disorders and schizophrenia, that levels of blood inflammation-related proteins before and after treatment might be useful in the diagnosis of psychiatric disorders or measuring responsiveness to drug treatment. Finally, it will be postulated how changes in these proteins affect CNS function to cause psychiatric disorders.

Neuroimmune pharmacology of neurodegenerative and mental diseases

Neuroimmune pharmacology is a newly emerging field that intersects with neuroscience, immunology, and pharmacology and that is seeking avenues for translational research and better understanding of disease mechanisms. It focuses on the immunity of the central nervous system (CNS) which is greatly influenced by endogenous effectors, such as cytokines and neurotransmitters, and by exogenous substances, including therapeutic compounds, infectious pathogens, and drugs of abuse. In this article, we attempt to raise awareness of the pivotal discovery of how those mediators affect the immunity of the CNS in both physiological conditions and processes of certain mental illnesses, including psychiatric disorders, neurodegenerative diseases, and cerebral dysfunctions due to drugs of abuse. The abnormality in cytokine networks, neurotransmitter homeostasis, and other immune responses may be involved in the neuropathology associated with those mental illnesses, and the therapeutic effects of the potential treatments can be attributed, at least partially, to their immunomodulatory activities. However, the resulting inflammatory cytokines from certain treatments frequently cause psychiatric complications. In addition, the poor neuropathological outcomes frequently found among drug abusers with HIV-1 infection appear to be related to the neurotoxic and immunomodulatory effects of the drugs used. Importantly, glial cells, especially microglia and astrocytes, are key players in the immunomodulatory activities in the CNS, and the functioning CNS is largely dependent upon the reciprocal interactions between neurons and glial cells. Therefore, glia-neuron interactions have become a critical issue for further understanding the disease mechanism. From this review, readers will gain insights into the new field of neuroimmune pharmacology, with a focus on the impacts of CNS immunity on the mental illnesses.

Ontogeny of sensorimotor gating and immune impairment induced by prenatal immune challenge in rats: implications for the etiopathology of schizophrenia

It has been hypothesized that the maternal immune response to infection may influence fetal brain development and lead to schizophrenia. Animal experimentation has supported this notion by demonstrating altered sensorimotor gating (prepulse inhibition, PPI) in adult rats prenatally exposed to an immune challenge. In the present study, pregnant rats were exposed to the bacterial endotoxin lipopolysaccharide (LPS) throughout gestation and the offspring were examined by evaluating the PPI, dopaminergic function, brain protein expression and cytokine serum levels from weaning to late adulthood. Prenatal LPS exposure induced a deficit in PPI that emerged at 'puberty' and that persisted throughout adult life. This prenatal insult caused age-specific changes in accumbal dopamine levels and in synaptophysin expression in the frontal cortex. Moreover, serum cytokine levels were altered in an age- and cytokine-dependent manner. Here we show that prenatal LPS administration throughout pregnancy causes maturation-dependent PPI deficits and age-dependent alterations in dopamine activity, as well as in synaptophysin expression and cytokine levels.

Longitudinal study of beta2-microglobulin abnormalities in schizophrenia

In an earlier cross-sectional study, we reported antipsychotic-naive schizophrenia patients to have significantly elevated beta2-microglobulin (beta2M) level suggestive of its potential association with the pathogenesis of schizophrenia. In this study, we present the follow-up analyses of beta2M in 31 patients from the previous study who were re-assessed after 92.1+/-7.2 days of antipsychotic treatment. Compared to baseline, there was a further significant elevation of beta2M in schizophrenia patients following treatment, especially in those who were treated with risperidone. Also, there was a significant negative correlation between beta2M level and total psychopathology score during follow-up in risperidone group. The study findings extend further support the role for beta2M in the pathogenesis of schizophrenia strengthening the case for immune dysregulation. Moreover, the observations suggest the possibility that the mechanism of action of antipsychotics might involve alteration of immune parameters.

Beta2-microglobulin abnormalities in antipsychotic-naïve schizophrenia: evidence for immune pathogenesis

Studies examining immune dysfunction in schizophrenia have reported decreased type-1 T-helper cell specific immunity (Th1) and increased type-2 T-helper cell specific immunity (Th2) and related abnormalities in inflammatory system. Beta2-Microglobulin (beta2M) influences the development of dendritic cells, which play a significant role in regulating the differentiation of naive CD4+ T cells into Th1 or Th2 lineages. The present study examined serum beta2M in antipsychotic-naïve schizophrenia patients (n=43) in comparison with age, sex, handedness and socioeconomic status matched healthy controls (n=43). Serum beta2M was significantly higher in schizophrenia patients (1692.6+/-354.4 ng/mL) than healthy controls (1409.6+/-246.9 ng/mL) (t=4.3; p<0.0001). There was a significant positive correlation between beta2M level and total psychopathology score (r=0.32; p=0.035). These novel observations suggest that beta2M abnormalities might have a potential association with the pathogenesis of schizophrenia.

Increased tumor necrosis factor-alpha concentrations with interleukin-4 concentrations in exacerbations of schizophrenia

Several studies have indicated that cytokines may be involved in the pathophysiology of schizophrenia. Previous studies, however, have yielded contradictory results; in this study we assess the plasma levels of both T-helper-1 (Th1) and T-helper-2 (Th2) cytokines in patients with acute exacerbations of schizophrenia. Plasma concentrations of interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha) and soluble receptor of interleukin-6 (sIL-6R) were measured with high sensitivity, enzyme-linked immunosorbent assays (ELISA) in patients with acute exacerbations of schizophrenia as compared with healthy controls. Patients with an acute exacerbation of schizophrenia had significantly increased production of TNF-alpha and significantly reduced production of IL-4 as compared with healthy subjects. No significant difference was observed in IL-6, sIL-6R, IL-8 and IL-10. Acute exacerbations of schizophrenia are associated with increased TNF-alpha concentrations (Th1) with concomitantly reduced concentrations of IL-4 (Th2) and a resulting increased TNF-alpha/IL-4 ratio.

Monocytic, Th1 and th2 cytokine alterations in the pathophysiology of schizophrenia

A growing body of evidence suggests that changes in the serum levels and cellular production of various cytokines are associated with the immunological abnormalities of schizophrenia. Several studies have examined alterations in T helper type 1 (Th1) and T helper type 2 (Th2) cytokines in schizophrenia. We explored monocytic, Th1 and Th2 cytokines in 43 schizophrenia patients and 50 normal controls. The mitogen-induced production of tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), IL-4, gamma-interferon (IFN-gamma) and IL-2 was measured with enzyme-linked immunosorbent assays before and after antipsychotic treatment. IL-6 and TNF-alpha production by schizophrenic patients was significantly higher than by normal controls, while IL-2, IL-4 and IFN-gamma production was significantly lower in schizophrenic patients. After 6 weeks of antipsychotic treatment, IL-6 and TNF-alpha production was significantly decreased, while IL-4, IFN-gamma and IL-2 productions were not significantly changed. Our results suggest that increased monocytic cytokines and decreased Th1 and Th2 cytokines may be associated with the immunopathogenesis of acute psychotic schizophrenia, and that antipsychotics may play an important role in immune response by decreasing elevated monocytic cytokines.

Neurobehavioral and immunological consequences of prenatal immune activation in rats. Influence of antipsychotics

Increasing evidence suggests that pre- or perinatal events that influence the immune system contribute to the development of behavioral or neuropsychiatric disorders. For instance, exposure of pregnant rats to the bacterial endotoxin lipopolysaccharide (LPS) disrupts sensorimotor information processing, as assessed by the prepulse inhibition test (PPI), and also the immune function in adult offspring, which might be of particular relevance as regards schizophrenia. However, the consequences of maternal LPS exposure during pregnancy on synaptic functioning in adult offspring and, more importantly, the therapeutic opportunity to re-establish PPI and immune function have still to be demonstrated. In this work, we analyzed the consequences of prenatal LPS exposure on dopaminergic neurotransmission and presynaptic markers in adult brain areas related to PPI circuitry. In addition, we tested whether oral treatment with the typical antipsychotic drug haloperidol (HAL) could reinstate PPI performances and cytokine serum levels in six-month-old male rats with prenatal LPS exposure. Both sensory information processing deficits and immune anomalies induced by prenatal exposure to LPS were accompanied by changes in dopaminergic neurotransmission and synaptophysin expression. It is important to note that PPI disruption and serum increases in cytokines induced by prenatal LPS exposure were both reversed by HAL. Taken together, these results demonstrate the critical influence of prenatal immune events on the functioning of adult nervous and immune systems, in association with the putative role of the immune system in the development of behavior relevant to schizophrenia.

Does treating schizophrenia reduce the chances of developing amyotrophic lateral sclerosis?

The development of amyotrophic lateral sclerosis (ALS) in the relatively common psychiatric disorder schizophrenia is very rare. This observation has been made by us and a number of other neuromuscular specialists at large ALS centers. We propose that the use of neuroleptics and some antidepressants, which are chronically prescribed to schizophrenics and which have neuroprotective properties and some of which promote neurogenesis, may confer protection against this deadly neurodegenerative disease ALS. Such an observation may have important implications towards the therapy and understanding the pathophysiology of this deadly neurodegenerative disease.