Cytokines production in chronic schizophrenia patients with or without paranoid behaviour

CTLA-4 expression and polymorphisms in Schizophrenia; a systematic review of literature

Schizophrenia constitutes a severe psychiatric disorder with detrimental impacts on individuals, their support systems, and the broader economy. Extensive research has revealed a notable association between variations in the Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) gene and an increased susceptibility to schizophrenia.This study represents the first systematic review of the literature investigating the impact of CTLA-4 polymorphisms and expression on the development and progression of schizophrenia.Our investigation involved a comprehensive search strategy, using a combination of title, abstract, and MESH terms in four databases, including PubMed, Scopus, Web of Science, and Google Scholar, until August 29th, 2023. The complete texts of the identified records were obtained and rigorously assessed based on predefined exclusion and inclusion criteria. Out of the numerous records, a total of 88 were identified through the databases. 10 studies met the criteria; therefore, their quality was assessed and included in this systematic study. The records were then categorized into polymorphism and expression groups. Our investigation emphasizes an association between rs3087243, rs231779, rs231777, rs16840252, rs5742909, and rs231775 polymorphisms and the development of schizophrenia. The results demonstrate a correlation between CTLA-4 polymorphisms and schizophrenia, compelling the need for further research to thoroughly examine the role of CTLA-4 in schizophrenia and other psychiatric disorders.

The Perspectives of Early Diagnosis of Schizophrenia Through the Detection of Epigenomics-Based Biomarkers in iPSC-Derived Neurons

The lack of early diagnostic biomarkers for schizophrenia greatly limits treatment options that deliver therapeutic agents to affected cells at a timely manner. While previous schizophrenia biomarker research has identified various biological signals that are correlated with certain diseases, their reliability and practicality as an early diagnostic tool remains unclear. In this article, we discuss the use of atypical epigenetic and/or consequent transcriptional alterations (ETAs) as biomarkers of early-stage schizophrenia. Furthermore, we review the viability of discovering and applying these biomarkers through the use of cutting-edge technologies such as human induced pluripotent stem cell (iPSC)-derived neurons, brain models, and single-cell level analyses.

Cytokine Imbalance in Schizophrenia. From Research to Clinic: Potential Implications for Treatment

Cytokines are one of the most important components of the immune system. They orchestrate the brain's response to infectious and other exogenous insults and are crucial mediators of the cross-talk between the nervous and immune systems. Epidemiological studies have demonstrated that severe infections and autoimmune disorders, in addition to genetic predisposition, are risk factors for schizophrenia. Furthermore, maternal infection during pregnancy appears to increase the risk of schizophrenia, and proinflammatory cytokines may be negatively involved in the neurodevelopmental process. A cytokine imbalance has been described in the blood and cerebrospinal fluid of schizophrenia patients, particularly in the T helper type 1 [Th1] and type 2 [Th2] cytokines, albeit the results of such studies appear to be contradictory. Chronic stress, likewise, appears to contribute to a lasting proinflammatory state and likely also promotes the disorder. The aim of this mini-review is to investigate the roles of different cytokines in the pathophysiology of schizophrenia and define how cytokines may represent key molecular targets to regulate for the prevention and treatment of schizophrenia. How current antipsychotic drugs impact cytokine networks is also evaluated. In this context, we propose to change the focus of schizophrenia from a traditionally defined brain disorder, to one that is substantially impacted by the periphery and immune system.

Single-nucleotide Polymorphism of CTLA-4 (rs5742909) in Correlation with Schizophrenia Risk Factor

Background

Cytotoxic T protein lymphocyte antigen-4 (CTLA-4) plays a key role in regulating the T-cell system, where occurrence of disturbances in the system seen by imbalances in Th1 and Th2 levels is believed to be one of the etiologies of schizophrenia. Single-nucleotide polymorphisms (SNPs) at rs5742909 in the CTLA-4 gene (C→T) might affect the expression level of CTLA-4 protein.

Aims and Objectives

The aim of this study was to determine the genotype distribution of the CTLA-4 gene (rs5742909) in patients with schizophrenia at Rumah Sakit Jiwa Prof. Dr. Soerojo Magelang and identify the correlation of these genetic polymorphisms as the risk factors of schizophrenia.

Materials and Methods

This research was conducted through the stage of submitting ethical approval, primer design, chromosomal DNA isolation, optimization of polymerase chain reaction conditions, and data analysis.

Results

Based on the results of the study, the CC genotype was shown in 36 patients (78.26%), TT genotype in 10 patients (21.73%), and no TT genotypes. However, statistical analysis using Fisher's exact and binary logistic regression statistical test showed no significant relationship between genetic polymorphism of the CTLA-4 rs5742909 against risk factors for schizophrenia (P = 0.05; α = 5%).

Conclusion

SNP at rs5742909, C-to-T-allele transition, was not significant associated with the risk of schizophrenia.

Increased ratio of high sensitivity C-reactive protein to interleukin-10 as a potential peripheral biomarker of schizophrenia and aggression

BACKGROUND

Many studies have indicated that immune dysfunction might be involved in the physiopathology of schizophrenia and aggression. This study aimed to investigate the correlation between high-sensitivity C-reactive protein (hsCRP), interleukin (IL)-10 and clinical characteristics, especially aggression, and to explore the potential role of hsCRP and IL-10 as plasma biomarkers of schizophrenia.

METHODS

Forty-one patients with schizophrenia and forty healthy individuals were enrolled. Psychopathological severity and aggression were assessed using the Positive and Negative Syndrome Scale (PANSS) and Modified Overt Aggression Scale (MOAS). Plasma concentrations of hsCRP and IL-10 were assessed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

(1) Higher levels of hsCRP (p<0.001), lower levels of logIL-10 (p<0.001) and higher ratio of hsCRP to IL-10 (p<0.001) were observed in the plasma of patients with schizophrenia, compared to healthy controls; (2) ROC (receiver operating characteristic) curve analysis revealed that ratio of hsCRP/IL-10 (predictive value: 0.783, p<0.01; sensitivity: 85.4%; specificity: 67.5%) was more applicable as a biomarker to distinguish patients with schizophrenia from the control group than hsCRP and IL-10 alone (predictive value: 0.718, p<0.01; 0.275, p<0.001, respectively); (3) we found positive correlations between hsCRP and the total score and verbal aggression score of MOAS (r=0.654, p<0.01; r=0.678, p<0.05), and between hsCRP/IL-10 and the total score of MOAS (r=0.636, p<0.01).

CONCLUSIONS

Our results suggest the possible function of hsCRP and IL-10 in the pathogenesis of schizophrenia and the possible value of hsCRP/IL-10 as a potential peripheral biomarker of schizophrenia. This finding also suggests a relationship between hsCRP, IL-10 and their ratio with aggression in patients with schizophrenia.

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.

Methodological Issues in Cytokine Measurement in Schizophrenia

There is mounting evidence that inflammation is a major factor in the pathophysiology of schizophrenia. Inflammatory status is commonly ascertained by measuring peripheral cytokine concentrations. An issue concerning research on inflammation and schizophrenia relates to assay methodology. Enzyme-linked immunosorbent assay (ELISA) is the most widely used and the gold standard method used to measure cytokine concentrations. ELISA has a number of limitations. Both ELISA and multiplex are limited by not being able to distinguish between bioactive and inactive molecules and the matrix and heterophilic (auto-) antibody interference. Multiplex assays when combined with gene expression analysis and flow cytometry techniques such as fluorescence-activated cell sorting may be useful to detect abnormalities in specific immune pathways. Peripheral blood mononuclear cells cultures, to evaluate in vitro lipopolysaccharide-induced cytokine production, may be a better technology than measuring cytokines in the serum. The purpose of this paper is to shed light on major methodological issues that need to be addressed in order to advance the study of cytokines in schizophrenia. We make a few recommendations on how to address these issues.

Sleep and inflammatory markers in different psychiatric disorders

Many psychiatric disorders, like schizophrenia, affective disorders, addictions and different forms of dementia are associated with sleep disturbances. In the etiology and course of those diseases inflammatory processes are regarded to be an increasingly important factor. They are also a frequently discussed element of the pathology of sleep. In this literature review reports on correlations between poor sleep and inflammatory responses in various psychiatric conditions are discussed. The link between schizophrenia, affective disorders and inflammatory cytokines is a complex phenomenon, which has been already confirmed in a number of studies. However, the presence of sleep deficits in those conditions, being a common symptom of depression and psychoses, can be an additional factor having a considerable impact on the immunological processes in mental illnesses. In the analyzed data, a number of studies are presented describing the role of inflammatory markers in sleep disturbances and psychopathological symptoms of affective, psychotic, neurogenerative and other disorders. Also attention is drawn to possible implications for their treatment. Efforts to use, e.g., anti-inflammatory agents in psychiatry in the context of their impact on sleep are reported. The aspect of inflammatory markers in the role of sleep deprivation as the treatment method in major depressive disorder is also discussed. A general conclusion is drawn that the improvement of sleep quality plays a crucial role in the care for psychiatric patients.

Effects of olanzapine on serum protein phosphorylation patterns in patients with schizophrenia

PURPOSE

Previous studies have shown that blood serum phosphoproteins are altered in schizophrenia patients in comparison to controls. However, it is not known whether phosphoproteins are also changed in response to treatment with antipsychotics.

EXPERIMENTAL DESIGN

Blood samples were taken from patients (n = 23) at baseline and after 6 weeks of olanzapine treatment. Immobilized metal ion affinity chromatography (IMAC) was used for enrichment of serum phosphoproteins and these were analyzed by label-free LC-MS in expression mode (LC-MS(E) ).

RESULTS

We identified 11 proteins that were changed significantly in overall abundance and 45 proteins that showed changes in phosphorylation after the antipsychotic treatment. The altered phosphoproteins were mainly involved in the acute phase response, lipid and glucose homeostasis (LXR), retinoic acid signaling (RXR), and complement pathways. Some of the proteins showed a marked increase in phosphorylation, including apolipoprotein A-I (3.4-fold), alpha-1-anti-chymotrypsin (3.1-fold), and apolipoprotein B-100 (2.2-fold). In addition, several proteins showed either decreased phosphorylation (e.g. complement C4A, collagen alpha-1 chain, complement factor H) or a mixture of increased and decreased phoshphorylation (e.g. afamin, complement C5, complement factor B). Finally, 24 of the altered phosphoproteins showed opposite directional changes in a comparison of baseline schizophrenia patients before and after treatment with olanzapine. These included alpha-1B-glycoprotein, apolipoprotein A-IV, vitamin D-binding protein, and prothrombin.

CONCLUSIONS AND CLINICAL RELEVANCE

These data demonstrate the potential for future studies of serum phosphoproteins as a readout of physiological function and might have utility in studies aimed at identification of biomarkers for drug response prediction or monitoring.

Increased Interleukin-17 and decreased BAFF serum levels in drug-free acute schizophrenia

Hypotheses regarding an immune-cytokine basis of schizophrenia have been postulated with controversial findings and a lack of data related to many cytokines. The aim of this study was to assess serum levels of Interferon-γ (IFN-γ), Interleukin-4 (IL-4), Transforming Growth Factor-β (TGF-β), Interleukin-17 (IL-17) and B-cell Activating Factor (BAFF) in schizophrenic patients and to determine correlations between cytokine levels and clinical parameters. Serum cytokine levels were measured with ELISA techniques in 60 neuroleptic-free patients on acute phase of the disease (BPRS≥40) and 28 healthy controls matched for age and sex. Current symptoms were assessed with Brief Psychiatric Rating Scale (BPRS), Positive and Negative Syndrome Scale (PANSS), Scale for the Assessment of Positive Symptoms (SAPS) and Scale for the Assessment of Negative Symptoms (SANS). No significant difference was found between patients and controls regarding IFN-γ serum levels. IL-4 was not detected in both groups. Patients exhibited significantly higher IL-17 and lower BAFF serum levels. IL-17 and BAFF levels were negatively correlated in schizophrenic patients. SANS global score was negatively correlated with IL-17 and positively correlated with IFN-γ serum levels. These results argue against the involvement of Th1 or Th2 population cells in schizophrenia. IL-17 and BAFF could be valuable markers for schizophrenia.

Genetic Variants of Interleukin-10 Gene Promoter are Associated with Schizophrenia in Saudi Patients: A Case-Control Study

BACKGROUND

Interleukin-10 (IL-10) gene is considered as a potential candidate gene in schizophrenia association studies. The polymorphisms on IL-10 gene have been reported to be linked with susceptibility to the development of schizophrenia within consistent results.

AIMS

The aim of this case-control study was to examine whether the -1082A/G, -819T/C, and -592A/C polymorphisms in IL-10 gene are implicated in schizophrenia development in the Saudi population.

MATERIALS AND METHODS

Molecular genotyping of IL-10 gene polymorphisms was performed to analyze the genotypes and alleles distribution of three single-nucleotide polymorphisms (SNPs) in patients (n = 181) and healthy individuals as control group (n = 211).

RESULTS

The frequencies of GA genotype at -1082, and CC genotype at positions -592 and -819 were significantly higher in schizophrenia patients compared to healthy subjects suggesting that GA, CC, and CC genotypes are susceptible to schizophrenia. The ACC haplotype known to be associated with intermediate production of IL-10 are more prevalent in our schizophrenia patients. On the other hand, genotypes -1082 GG, -819 CT, and -592 CA of IL-10 were more prevalent in healthy controls suggesting protective effects of GA, CT, and CA genotypes against schizophrenia. There was no significant association of IL-10 polymorphisms with sex or positive or negative symptoms of schizophrenia.

CONCLUSION

This study indicates that the IL-10 gene polymorphisms play a significant role in the etiology of schizophrenia in Saudi Arabians patients.

Immune system: a possible nexus between cannabinoids and psychosis

BACKGROUND

Endocannabinoid system is involved in the regulation of the brain-immune axis. Cannabis consumption is related with the development, course, and severity of psychosis. The epidemiological evidence for increased occurrence of immunological alterations in patients with psychosis has not been sufficiently addressed. The aim of this review is to establish whether there is any scientific evidence of the influence of cannabinoids on aspects of immunity that affect susceptibility to psychotic disorder induction.

METHODS

A comprehensive search of PubMed/MEDLINE, EMBASE and ISI Web of Knowledge was performed using combinations of key terms distributed into three blocks: "immune", "cannabinoid", and "endocannabinoid receptor". Studies were considered to be eligible for the review if they were original articles, they reported a quantitative or qualitative relation between cannabinoid ligands, their receptors, and immune system, and they were carried out in vitro or in mammals, included humans. All the information was systematically extracted and evaluated.

RESULTS

We identified 122 articles from 446 references. Overall, endocannabinoids enhanced immune response, whereas exogenous cannabinoids had immunosuppressant effects. A general change in the immune response from Th1 to Th2 was also demonstrated for cannabinoid action. Endogenous and synthetic cannabinoids also modulated microglia function and neurotransmitter secretion.

CONCLUSION

The actions of cannabinoids through the immune system are quite regular and predictable in the peripheral but remain fuzzy in the central nervous system. Despite this uncertainty, it may be hypothesized that exposure to exocannabinoids, in particular during adolescence might prompt immunological dysfunctions that potentially cause a latent vulnerability to psychosis. Further investigations are warranted to clarify the relationship between the immunological effects of cannabis and psychosis.

Decreased interleukin-10 serum levels in first-episode drug-naïve schizophrenia: relationship to psychopathology

Many lines of findings support the hypothesis of the inflammation-related pathways in the multifactorial pathogenesis of schizophrenia (SZ). Interleukin-10 (IL-10), a potential anti-inflammatory cytokine, was found to be altered in chronic patients with SZ. The aim of this study was to assess the serum levels of IL-10 in first-episode and drug-naïve (FEDN) patients with SZ and its relationships with the psychopathological parameters. Serum IL-10 levels were analyzed using established procedures in 128 FEDN patients with SZ and 62 healthy controls. Schizophrenia symptoms were assessed by the Positive and Negative Syndrome Scale (PANSS) with cognitive factor derived from the five factor model of the PANSS. Compared to the healthy controls, the patients exhibited a significant decrease in IL-10 levels. Serum IL-10 was inversely correlated with the PANSS negative symptom, as well as with the PANSS cognitive factor subscores in patients. Our results suggested that decreased IL-10 may be implicated in the negative symptom and cognitive impairment at the acute stage of schizophrenia episode.

Effects of antipsychotics on the inflammatory response system of patients with schizophrenia in peripheral blood mononuclear cell cultures

OBJECTIVE

We investigated the effects of antipsychotics on immune-challenged peripheral blood mononuclear cell (PBMC) cultures.

METHODS

Blood samples were collected from twelve patients with first-episode schizophrenia. The PBMCs were separated and cultures were prepared and stimulated with lipopolysaccharide (LPS) or polyinosinic:polycytidylic acid (poly[I:C]), and then separately treated with a typical antipsychotic (haloperidol) or atypical antipsychotic (clozapine, quetiapine, or risperidone). Pro-inflammatory (interferon gamma [IFN-γ]) and anti-inflammatory (interleukin [IL]-4 and IL-10) cytokine levels were measured in the LPS- or poly(I:C)-stimulated PBMC cultures treated with antipsychotics.

RESULTS

Haloperidol and quetiapine significantly increased the IL-4 levels (p<0.05) in LPS-stimulated PBMC cultures, while clozapine and quetiapine significantly enhanced the IL-4 levels (p<0.05) in poly(I:C)-stimulated PBMC cultures. Only treatment with haloperidol resulted in a significant increase in IL-10 production (p<0.05) in LPS-stimulated PBMC cultures, whereas clozapine, quetiapine, and risperidone treatment significantly increased IL-10 production (p<0.05) in poly(I:C)-stimulated PBMC cultures. All of the antipsychotics reduced the IFN-γ level significantly (p<0.05) in LPS- and poly(I:C)-stimulated PBMC cultures.

CONCLUSION

Antipsychotic treatment altered immune function by raising the levels of anti-inflammatory cytokines (IL-4 and IL-10) and suppressing the levels of pro-inflammatory cytokines (IFN-γ).

Differential correlations between inflammatory cytokines and psychopathology in veterans with schizophrenia: potential role for IL-17 pathway

Pro-inflammatory cytokines have been consistently reported to be elevated in schizophrenia patients. However, it is not known whether cytokines influence the presentation of psychotic symptoms. To address this issue, we evaluated the relationship between levels of inflammatory molecules and psychopathological parameters in patients with schizophrenia. We hypothesized that severity of symptoms would correlate with increased levels of inflammatory cytokines. Serum samples from 47 veterans with a diagnosis of schizophrenia and 20 healthy controls were tested for levels of 38 cytokines/chemokines involved in regulation of immune/inflammatory reactions using a Millipore multiplex bead array in a Luminex 100 system. We found significantly increased levels of GRO, MCP-1, MDC, and sCD40L, and significantly decreased levels of IFN-γ, IL-2, IL-12p70, and IL-17, in schizophrenia patients compared to controls. In addition, we observed positive correlations between levels of cytokines and the Positive and Negative Symptoms Scale (PANSS) scores in subjects with schizophrenia for G-CSF, IL-1β, IL1ra, IL-3, IL-6, IL-9, IL-10, sCD40L and TNF-β. Pathway analyses showed these cytokines to be part of the IL17 pathway. Using principal component analyses, we found the factor that included these cytokines and IL-17 to be associated with positive, general and total PANSS scores. These results suggest that alterations in this pathway may play a role in development of psychotic symptoms in schizophrenia.

The interaction of polymorphisms of IL10 and DBH was associated with general symptoms of PANSS with TD in Chinese Han schizophrenic patients

OBJECTIVE

Tardive dyskinesia (TD) is a human hyperkinetic movement disorder as a result of potentially irreversible long-term chronic first-generation antipsychotic medications. Unfortunately, mechanisms involved in the development of TD have been poorly understood. Previous studies have indicated that some genetic polymorphisms of immune system and dopamine beta-hydroxylase (DBH) genes may be involved in the pathogenesis of TD. Rs1800872 and rs72393728 are located on the promoter of interleukin-10 (IL10) and DBH gene, respectively. The genetic association between the rs1800872 and TD is unclear. Previous studies have indicated that genetic variations of IL 10 and DBH are implicated in the positive and negative symptoms in schizophrenia. However, the interaction of two variations with severity of TD and symptoms of schizophrenic patients with TD has not been reported. The present study investigated whether these variations and their interaction were associated with clinical phenotypes of TD with schizophrenia in a genetically homogeneous northern Chinese Han population.

METHODS

Rs1800872 and rs72393728 were genotyped in schizophrenic patients with TD (n = 372) and without TD (NTD; n = 412). The Abnormal Involuntary Movement Scale (AIMS) and Positive and Negative Syndrome Scale (PANSS) were applied to assess the severity of TD and psychopathology of schizophrenia, respectively.

RESULTS

The allele and genotype frequencies of rs1800872 and rs72393728 did not significantly differ between TD and NTD patients (p>0.05). No significant difference was found in the AIMS total score among the genotypes of two loci (p>0.05). Interestingly, the interaction of rs1800872 and rs72393728 showed a significant association with the PANSS general score (p = 0.011), and a trend toward to the PANSS total score (p = 0.055).

CONCLUSION

These findings suggest that the interaction of rs1800872 and rs72393728 variants may play a role in psychopathology of the general symptoms on PANSS in schizophrenic patients with TD in a northern Chinese Han population.

Inflammation and schizophrenia: alterations in cytokine levels and perturbation in antioxidative defense systems

OBJECTIVE

Although several theories have been proposed including developmental/neurodegenerative processes, neurotransmitter abnormalities, viral infection, and immune dysfunction, the exact causative factor of schizophrenia is unclear. A relationship between inflammation and schizophrenia has been supported by abnormal cytokine production and altered antioxidant status. This study was aimed to examine the alterations in serum oxidative-antioxidative status and cytokine levels of schizophrenic patients.

METHODS

A total of 91 schizophrenic patients from Saudi Arabia and 50 age- and sex-matched healthy controls were enrolled in the present study. Fresh blood samples were collected to measure the levels of cytokines and markers of oxidative stress by spectrophotometric assays simultaneously.

RESULTS

We observed that there was a significant increase in the levels of tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 and a decrease in the levels of interferon-γ. Lipid peroxides are elevated in serum, while total-sulfhydryl levels were decreased. Also, the activities of superoxide dismutase and glutathione peroxidase were decreased, while the activities of catalase, glutathione reductase, and myeloperoxidase were found to be elevated in serum.

CONCLUSION

We conclude that inflammation resulting from dysregulation of cytokines and altered antioxidant systems may play a critical role in the etiology of schizophrenia.

Anti-inflammatory treatment in schizophrenia

Antipsychotics, which act predominantly as dopamine D2 receptor antagonists, have several shortcomings. The exact pathophysiological mechanism leading to dopaminergic dysfunction in schizophrenia is still unclear, but inflammation has been postulated to be a key player in the pathophysiology of the disorder. A dysfunction in activation of the type 1 immune response seems to be associated with an imbalance in tryptophan/kynurenine metabolism; the degrading enzymes involved in this metabolism are regulated by cytokines. Kynurenic acid (KYNA), an N-methyl-d-aspartate antagonist, was found to be increased in critical regions of the central nervous system (CNS) in schizophrenia, resulting in reduced glutamatergic neurotransmission. The differential activation of microglial cells and astrocytes as functional carriers of the immune system in the CNS may also contribute to this imbalance. The immunological effects of many existing antipsychotics, however, rebalance in part the immune imbalance and overproduction of KYNA. The immunological imbalance results in an inflammatory state combined with increased prostaglandin E(2) production and increased cyclo-oxygenase-2 (COX-2) expression. Growing evidence from clinical studies with COX-2 inhibitors points to favorable effects of anti-inflammatory therapy in schizophrenia, in particular in an early stage of the disorder. Further options for immunomodulating therapies in schizophrenia will be discussed.

Cytokines, neurophysiology, neuropsychology, and psychiatric symptoms

Recent research has overcome the old paradigms of the brain as an immunologically privileged organ, and of the exclusive role of neurotransmitters and neuropeptides as signal transducers in the central nervous system. Growing evidence suggests that the signal proteins of the immune system - the cytokines - are also involved in modulation of behavior and induction of psychiatric symptoms. This article gives an overview on the nature of cytokines and the proposed mechanisms of immune-to-brain interaction. The role of cytokines in psychiatric symptoms, syndromes, and disorders like sickness behavior, major depression, and schizophrenia are discussed together with recent immunogenetic findings.

Inflammation in schizophrenia

Although there is no doubt that the dopaminergic neurotransmission is strongly involved in the pathophysiology of schizophrenia, the exact mechanism leading to dopaminergic dysfunction is still unclear. A disbalance in the immune response associated with a slight inflammatory process of the central nervous system (CNS) has been postulated. Such a mechanism is the basis for the "mild encephalitis" concept. A dysfunction in the activation of the type-1 immune response seems to be associated with decreased activity of the key enzyme of the tryptophan/kynurenine metabolism, indoleamine 2,3-dioxygenase (IDO). Theoretically, a decreased activity of IDO results in the increased production of kynurenic acid, an N-methyl-D-aspartate antagonist in the CNS, and a reduced glutamatergic neurotransmission in schizophrenia. Accordingly, in animal models of schizophrenia, increased levels of kynurenic acid in critical regions of the CNS were described, although studies of peripheral blood levels of kynurenic acid in schizophrenic patients showed controversial results. The immunological effects of a lot of existing antipsychotics, however, rebalance in part the immune imbalance and the overweight of the production of kynurenic acid. The inflammatory state in schizophrenia is associated with increased prostaglandin E(2) production and increased cyclooxygenase-2 (COX-2) expression. Growing evidence from clinical studies with COX-2 inhibitors points to favorable effects of anti-inflammatory therapy in schizophrenia, in particular in an early stage of the disorder. Further options for immunomodulating therapies in schizophrenia will be discussed.

Impact of antipsychotics on cytokine production in-vitro

OBJECTIVE

A growing body of data from genetic, immunological and clinical studies indicates an involvement of the immune system in the pathophysiology of schizophrenia and suggests that the modulation of the cytokine system by antipsychotics may be one cause for the improvement of psychotic symptoms. However, the influence of the typical antipsychotics chlorpromazine and haloperidol, and the effect of typical and atypical antipsychotics on the TSST-1-stimulated blood cell secretion of cytokines, and specifically the interleukin (IL)-17 production have not been studied so far, although IL-17 is a leading pro-inflammatory cytokine.

METHOD

We measured levels of IL-1β, IL-2, IL-4, IL-6, IL-17 and tumor necrosis factor-α (TNF-α) in stimulated blood of 10 healthy female subjects in a whole blood assay using the toxic shock syndrome toxin TSST-1 as stimulant. Blood was either supplemented with antipsychotics (chlorpromazine, haloperidol, clozapine, N-desmethylclozapine and quetiapine with four different concentrations each) or not.

RESULTS

Under TSST-1 stimulation, antipsychotics as a group had no influence on IL-1β or IL-6 concentrations but increased IL-4 levels. The most consistent findings were seen regarding IL-17. Mean IL-17 concentrations differed significantly between blood with and without antipsychotic supplements and were increased over all antipsychotics and almost all of the applied antipsychotic concentrations. TNF-α levels were increased by chlorpromazine; N-desmethylclozapine and quetiapine reduced IL-2 production.

CONCLUSIONS

Antipsychotics might, among other mechanisms, act as such by increasing the production of IL-17.

Antioxidants, redox signaling, and pathophysiology in schizophrenia: an integrative view

Schizophrenia (SZ) is a brain disorder that has been intensively studied for over a century; yet, its etiology and multifactorial pathophysiology remain a puzzle. However, significant advances have been made in identifying numerous abnormalities in key biochemical systems. One among these is the antioxidant defense system (AODS) and redox signaling. This review summarizes the findings to date in human studies. The evidence can be broadly clustered into three major themes: perturbations in AODS, relationships between AODS alterations and other systems (i.e., membrane structure, immune function, and neurotransmission), and clinical implications. These domains of AODS have been examined in samples from both the central nervous system and peripheral tissues. Findings in patients with SZ include decreased nonenzymatic antioxidants, increased lipid peroxides and nitric oxides, and homeostatic imbalance of purine catabolism. Reductions of plasma antioxidant capacity are seen in patients with chronic illness as well as early in the course of SZ. Notably, these data indicate that many AODS alterations are independent of treatment effects. Moreover, there is burgeoning evidence indicating a link among oxidative stress, membrane defects, immune dysfunction, and multineurotransmitter pathologies in SZ. Finally, the body of evidence reviewed herein provides a theoretical rationale for the development of novel treatment approaches.

ATA homozigosity in the IL-10 gene promoter is a risk factor for schizophrenia in Spanish females: a case control study

Background

Three IL-10 gene promoter single nucleotide polymorphisms -1082G > A, -819C > T and -592C > A and the haplotypes they define in Caucasians, GCC, ACC, ATA, associated with different IL-10 production rates, have been linked to schizophrenia in some populations with conflicting results. On the basis of the evidence of the sex-dependent effect of certain genes in many complex diseases, we conducted a sex-stratified case-control association study to verify the linkage of the IL-10 gene promoter SNPs and haplotypes with schizophrenia and the possible sex-specific genetic effect in a Spanish schizophrenic population.

Methods

241 DSM-IV diagnosed Spanish schizophrenic patients and 435 ethnically matched controls were genotyped for -1082G > A and -592C > A SNPs. Chi squared tests were performed to assess for genetic association of alleles, genotypes and haplotypes with the disease.

Results

The -1082A allele (p = 0.027), A/A (p = 0.008) and ATA/ATA (p = 0.003) genotypes were significantly associated with schizophrenia in females while neither allelic nor genotypic frequencies reached statistical significance in the male population.

Conclusions

Our results highlight the hypothesis of an imbalance towards an inflammatory syndrome as the immune abnormality of schizophrenia. Anyway, a better understanding of the involvement of the immune system would imply the search of immune abnormalities in endophenotypes in whose sex and ethnicity might be differential factors. It also reinforces the need of performing complex gene studies based on multiple cytokine SNPs, including anti and pro-inflammatory, to clarify the immune system abnormalities direction in the etiology of schizophrenia.

CTLA-4 confers a risk of recurrent schizophrenia, major depressive disorder and bipolar disorder in the Chinese Han population

Previous studies have reported that the cytotoxic T lymphocyte antigen-4 (CTLA-4) gene, which is related to immunological function such as T-cell regulation, is associated with psychiatric disorders. In this study, we studied the relationship between CTLA-4 and three major psychiatric disorders, schizophrenia, major depressive disorder and bipolar disorder in the Chinese Han population. We recruited 1140 schizophrenia patients, 1140 major depressive disorder patients, 1140 bipolar disorder patients, and 1140 normal controls to examine the risk conferred by 6 tag SNPs (rs231777, rs231775, rs231779, rs3087243, rs5742909, rs16840252) in the CTLA-4 gene. We found that rs231779 conferred a risk for schizophrenia (P(allele)=0.0003, P(genotype)=0.0016), major depressive disorder (P(allele)=0.0006, P(genotype)=0.0026) and bipolar disorder (P(allele)=0.0004, P(genotype)=0.0018). In addition, rs231777 and rs16840252 had a significant association with schizophrenia (rs231777: P(allele)=0.0201, rs16840252: P(allele)=0.0081, P(genotype)=0.0117), and rs231777 had significant association with bipolar disorder (rs231777: P(allele)=0.0199). However, after 10,000 permutations, only rs231779 remained significant (schizophrenia: P(allele)=0.0010, P(genotype)=0.0145, major depressive disorder: P(allele)=0.0010, P(genotype)=0.0201, bipolar disorder: P(allele)=0.0008, P(genotype)=0.0125). Our results suggest that shared common risk factors for schizophrenia, major depressive disorder and bipolar disorder exist in the CTLA-4 gene in the Chinese Han population.

Converging evidence of blood-based biomarkers for schizophrenia: an update

This chapter has carried out a review of the literature and combined this with the results of in-house studies to identify candidate blood-based biomarkers for schizophrenia and antipsychotic drug response. Literature searches retrieved 185 publications describing a total of 273 schizophrenia biomarkers identified in serum and/or plasma. Examination of seven in-house multicenter studies resulted in the identification of 137 serum/plasma biomarkers. Taken together, the findings suggested an ongoing immunological and inflammatory process in schizophrenia. This was accompanied by altered cortisol levels which suggested activated stress response and altered hypothalamic-pituitary-adrenal axis function in these patients. The authors conclude that such biomarkers may prove useful as additional parameters for characterizing specific immune and/or metabolic or hormonal subsystems in schizophrenia and might, therefore, facilitate the development of future patient stratification and personalized medicine strategies.

Immune System and Schizophrenia

Although an immune dysfunction and the involvement of infectious agents in the pathophysiology of schizophrenia are discussed since decades, the field never came into the mainstream of research. In schizophrenia a blunted type-1 immune response seems to be associated with a dysbalance in the activation of the enzyme indoleamine 2,3-dioxygenase (IDO) and in the tryptophan - kynurenine metabolism resulting in increased production of kynurenic acid in schizophrenia. This is associated with an imbalance in the glutamatergic neurotransmission, leading to an NMDA antagonism in schizophrenia. The immunological effects of antipsychotics rebalance partly the immune imbalance and the overweight of the production of the kynurenic acid. This immunological imbalance results in an inflammatory state combined with increased prostaglandin E(2) (PGE(2)) production and increased cyclo-oxygenase-2 (COX-2) expression. COX-2 inhibitors have been tested in clinical trials, pointing to favourable effects in schizophrenia.

The impact of neuroimmune dysregulation on neuroprotection and neurotoxicity in psychiatric disorders--relation to drug treatment

An inflammatory pathogenesis has been postulated for schizophrenia and major depression (MD). In schizophrenia and depression, opposing patterns oftype-1 vs type-2 immune response seem to be associated with differences in the activation of the enzyme indoleamine 2,3-dioxygenase and in the tryptophan-kynurenine metabolism, resulting in increased production of kynurenic acid in schizophrenia and decreased production of kynurenic acid in depression. These differences are associated with an imbalance in the glutamatergic neurotransmission, which may contribute to an excessive agonist action of N-methyl-D-aspartate (NMDA) in depression and of NMDA antagonism in schizophrenia. Regarding the neuroprotective function of kynurenic acid and the neurotoxic effects of quinolinic acid (QUIN), different patterns of immune activation may also lead to an imbalance between the neuroprotective and the neurotoxic effects of the tryptophanlkynurenine metabolism. The differential activation of microglia cells and astrocytes may be an additional mechanism contributing to this imbalance. The immunological imbalance results in an inflammatory state combined with increased prostaglandin E2 production and increased cyclo-oxygenase-2 (COX-2) expression. The immunological effects of many existing antipsychotics and antidepressants, however, partly correct the immune imbalance and the excess production of the neurotoxic QUIN, COX-2 inhibitors have been tested in animal models of depression and in preliminary clinical trials, pointing to favorable effects in schizophrenia and in MD.

Decreased serum levels of interleukin-2 and interleukin-6 in Indian Bengalee schizophrenic patients

BACKGROUND AND PURPOSE

Autoimmune process is thought to be involved in the pathophysiology in some cases of schizophrenia. Alteration in interleukin (IL) regulation is regarded as additional proof of autoimmunological background in schizophrenia. Most of the research in interleukin activity in schizophrenia has been in Caucasian and some Mongoloid patients. We have studied the serum IL-2 and IL-6 level in psychotropic medication free and antipsychotic medicating schizophrenic patients who are Indian Bengalee by ethnicity.

METHOD

Twenty psychotropic medication free and 30 antipsychotic medicating schizophrenic patients who fulfilled DSM-IV-TR criteria and 30 of the same age and sex matched controls were recruited. Serum level of IL-2 and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA).

RESULT

There was a significant decrease of IL-2 and IL-6 in both antipsychotic medicating and psychotropic medication free patients. Further the medicating patients showed lower level of IL-2 and IL-6 than the psychotropic medication free patients.

CONCLUSION

This is the first study to describe a decrease serum level of IL-6 in schizophrenic patients. The study provides the evidence that some kind of immune dysregulation is involved in pathophysiology of schizophrenia. The study also provides the evidence for the immunosuppressive effect of antipsychotic drugs.

Association study of interleukin 2 (IL2) and IL4 with schizophrenia in a Japanese population

Interleukin 2 (IL-2) and IL-4 are pleiotropic cytokines regulating Th1/Th2 balance and have a regulatory activity in brain function. Thus these cytokines have been implicated in the pathophysiology of schizophrenia. The latest studies provided controversial results regarding the genetic associations of these cytokines. The functional polymorphisms, IL2-330T/G and IL4-590C/T, were associated with schizophrenia in a German population, although contradictory findings were also reported in a Korean population. To ascertain whether IL2 and IL4 contribute to vulnerability to schizophrenia, we conducted a moderate-scale case-control (536 patients and 510 controls) association study for seven polymorphisms in Japanese subjects. There were no significant associations of these genes with schizophrenia using either single marker or haplotype analyses. The present study suggests that IL2 and IL4 do not contribute to vulnerability to schizophrenia in the Japanese population.

A psychoneuroimmunological perspective to Emil Kraepelins dichotomy: schizophrenia and major depression as inflammatory CNS disorders

The Kraepelinian classification of psychiatric disorders, in particular the dichotomy of dementia praecox and manic-depressive psychosis is under discussion since a long time. In recent years, not only new research in the fields of psychopathology and clinical outcome, but also findings of biological markers in the areas of neurophysiology, neuroendocrinology, psychoneuroimmunology, genetics, or psychopharmacology show a big overlap between both groups of disorders. This overlap of symptoms and markers of both disorders intensified the discussion and the proposals for new criteria for the classification of psychiatric disorders. By means of findings from the field of psychoneuroimmunology and inflammation it will be shown that different pathological mechanisms in depression and schizophrenia may lead to the same final common pathway of inflammation. These mechanisms include the immunological balance between type-1 and type-2 immune activation which influences the tryptophan-degradating enzyme indoleamine 2,3-dioxygenase (IDO) in the CNS in opposite ways, leading to an altered availability of tryptophan and serotonin, and a disturbance of the kynurenine metabolism with an imbalance in favor of the production of the NMDA-receptor agonist quinolinic acid in depression and of the NMDA-receptor antagonist kynurenic acid in schizophrenia. In both disorders, however, an increased production of prostaglandin E2 and increased expression of cyclo-oxygenase-2 reflect a slight inflammatory process taking place probably in different regions of the CNS. Albeit this common inflammatory pathway--inflammation is a general pathway of the body as answer to a lot of different noxae and pathogens--the Kraepelinian dichotomy is important with respect to pathological mechanisms and therapeutic approaches, not only for further research in understanding the exact pathological mechanisms but also for the development of preventive strategies in high risk individuals and in patients. Opposite pathways regarding the immune activation, the neurotoxic versus neuroprotective kynurenine metabolites and the agonistic versus antagonistic effects on the NMDA receptor and the glutamatergic neurotransmission show despite a possible therapeutic advantage of anti-inflammatory therapy in both disorders that the Kraepelinian dichotomy still has a significant value from a biologic-psychiatric point of view.

Inflammatory cytokine alterations in schizophrenia: a systematic quantitative review

BACKGROUND

Cytokines play an important role in infection and inflammation and are crucial mediators of the cross-talk between the brain and the immune system. Schizophrenia would be associated with an imbalance in inflammatory cytokines, leading to a decrease in Th1 and an increase in Th2 cytokine secretion. However, data published so far have been inconsistent. The primary objective of the present meta-analysis was to verify whether the cytokine imbalance hypothesis of schizophrenia is substantiated by evidence.

METHODS

Cross-sectional studies were included if they assessed in vivo plasma or serum cytokine concentrations and/or in vitro secretion of cytokines by peripheral blood leukocytes from schizophrenia patients and healthy volunteers.

RESULTS

Data from 62 studies involving a total sample size of 2298 schizophrenia patients and 1858 healthy volunteers remained for analysis. Ten cytokines were assessed, including the prototypic Th1 and Th2 cytokines gamma interferon (IFN-gamma) and interleukin 4 (IL-4) as well as IL-2, soluble IL-2 receptor (sIL-2R), IL-1beta, IL-1 receptor antagonist (IL-1RA), tumor necrosis factor-alpha (TNF-alpha), IL-6, soluble IL-6 receptor (sIL-6R), and IL-10. The results show that an increase occurs in in vivo IL-1RA, sIL-2R, and IL-6 and a decrease occurs in in vitro IL-2 in schizophrenia. No significant effect sizes were obtained for the other cytokines.

CONCLUSIONS

These findings provide the first evidence of establishment of an inflammatory syndrome in schizophrenia, which refutes the current hypothesis of a Th2 slant. Caveats are presented to data interpretation, including the role of stress and the effect of weight gain that develops in schizophrenia.

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.

Interleukin-12 plasma levels in drug-naïve patients with a first episode of psychosis: effects of antipsychotic drugs

An overactivation of the Th1 activity in schizophrenia had been described. Interleukin-12 (IL-12), a proinflammatory cytokine, plays a key role in the regulation of the Th1 response. The aims of this study were to investigate the effect of first and second generation antipsychotic drugs on IL-12 production during the acute phase of the illness and its association with clinical features. Participants comprised 56 drug-naïve first episode psychotic patients and 28 healthy volunteers. Patients were initially randomly assigned to risperidone (n=16), olanzapine (n=20) or haloperidol (n=20); subject were maintained on the same medication throughout the study. Clinical assessments were conducted at baseline and at 6 weeks. IL-12 plasma levels were assessed at baseline and after 6 weeks of antipsychotic treatment. IL-12 haplotypes were also analysed. Patients showed higher IL-12 plasma levels at baseline compared with controls, and had a significant increase in IL-12 plasma level after 6 weeks of antipsychotic treatment. No significant differences in IL-12 level increase were found among the three antipsychotic treatments. IL-12 plasma levels at week 6 were not significantly associated with the severity of psychopathology at week 6. Thus, patients with a first episode of psychosis have inflammatory-like immunological function during early phases of the illness that it is independent of the antipsychotic treatment used.

Tourette's syndrome is not associated with interleukin-10 receptor 1 variants on chromosome 11q23.3

Interleukin-10 receptor 1 (IL-10R1) single nucleotide polymorphisms, located on chromosome 11q23 - a strong candidate for linkage with Tourette's syndrome (TS) - have been investigated for association with TS. DNA of 77 patients with a DSM-IV (Diagnostic and Statistical Manual IV) diagnosis of TS and 250 healthy controls was genotyped. IL-10R1 was not associated with TS.

The immunological basis of glutamatergic disturbance in schizophrenia: towards an integrated view

This overview presents a hypothesis to bridge the gap between psychoneuroimmunological findings and recent results from pharmacological, neurochemical and genetic studies in schizophrenia. In schizophrenia, a glutamatergic hypofunction is discussed to be crucially involved in dopaminergic dysfunction. This view is supported by findings of the neuregulin- and dysbindin genes, which have functional impact on the glutamatergic system. Glutamatergic hypofunction is mediated by NMDA (N-methyl-D-aspartate) receptor antagonism. The only endogenous NMDA receptor antagonist identified up to now is kynurenic acid (KYN-A). KYN-A also blocks the nicotinergic acetycholine receptor, i.e. increased KYN-A levels can explain psychotic symptoms and cognitive deterioration. KYN-A levels are described to be higher in the CSF and in critical CNS regions of schizophrenics. Another line of evidence suggests that of the immune system in schizophrenic patients is characterized by an imbalance between the type-1 and the type-2 immune responses with a partial inhibition of the type-1 response, while the type-2 response is relatively over-activated. This immune constellation is associated with the inhibition of the enzyme indoleamine 2,3-dioxygenase (IDO), because type-2 cytokines are potent inhibitors of IDO. Due to the inhibition of IDO, tryptophan is predominantly metabolized by tryptophan 2,3-dioxygenase (TDO), which is located in astrocytes, but not in microglia cells. As indicated by increased levels of S100B, astrocytes are activated in schizophrenia. On the other hand, the kynurenine metabolism in astrocytes is restricted to the dead-end arm of KYN-A production. Accordingly, an increased TDO activity and an accumulation of KYN-A in the CNS of schizophrenics have been described. Thus, the immune-mediated glutamatergic-dopaminergic dysregulation may lead to the clinical symptoms of schizophrenia. Therapeutic consequences, e.g. the use of antiinflammatory cyclooxygenase-2 inhibitors, which also are able to directly decrease KYN-A, are discussed.

[Immunology in schizophrenic disorders]

This manuscript deals with whether immune-mediated mechanisms of inflammation contribute to the pathogenesis of schizophrenia. A model is presented which integrates psychoneuroimmunologic findings and actual results from pharmacological, neurochemical, and genetic studies in schizophrenia. A pivotal role in the neurobiology of schizophrenia is played by dopaminergic neurotransmission, which is modulated by influences of the glutamatergic system. The decreased function of the glutamate system described in schizophrenia seems primarily mediated by N-methyl-D-aspartate (NMDA) receptor antagonism. Kynurenine acid is the only known endogenous NMDA receptor antagonist. In higher concentrations it blocks the NMDA receptor, but in lower concentrations it blocks the nicotinergic acetylcholin receptor, which has a prominent role in cognitive functions. Therefore, higher levels of kynurenine acid may explain psychotic symptoms and cognitive dysfunction. Several findings point out that prenatal infection, associated with an early sensitisation of the immune system, may result in an imbalance of the immune response (type 1 vs type 2) in schizophrenia. This immune constellation leads to inhibition of the enzyme indoleamin dioxigenase (IDO). It and tryptophane 2,3-dioxygenase (TDO) both catalyse the degradation from tryptophan to kynurenine. Due to the inhibition of IDO, tryptophan is metabolised to kynurenine primarily by TDO. In the CNS, TDO is located only in astrocytes, which are in particular activated in schizophrenia and in which kynurenine acid is the final product and can not be further metabolised. Therefore kynurenine acid accumulates in the CNS of schizophrenics and - due to its NMDA-antagonistic properties - leads to cognitive dysfunction and psychotic symptoms. This model describes the pathway of immune-mediated glutamatergic-dopaminergic dysregulation, which may lead to the clinical symptoms of schizophrenia. Therapeutic consequences (e.g. cyclo-oxygenase-2 inhibitors) are discussed.

T- and B-lymphocytes in patients with schizophrenia in acute psychotic episode and the course of the treatment

Schizophrenia is associated with alterations of the immune system. There are, however, only limited data dealing with immune parameters in unmedicated schizophrenic patients and the course of these parameters during treatment. In this study, we monitored CD19+ (B)- and CD3+ (T)-lymphocytes in the course of antipsychotic treatment. Forty patients diagnosed with an acute exacerbation of schizophrenia were tested before and after 3 days, 2 weeks, 4 weeks and 3 months of treatment with antipsychotics. The percentages of CD19+- and CD3+ -lymphocytes were analysed by flow cytometry using fluorescence conjugated anti-CD19 and anti-CD3 antibodies. Twenty healthy volunteers served as controls. In the acute state of psychosis, a significant reduction of the CD3+ -lymphocyte subpopulation was observed, while the percentage of CD19(+)-lymphocytes was increased. Both subpopulations levelled to those of the control group in the course of treatment. As expected, the levels of the immune parameters did not change in the healthy controls during the course of the study. The observed alterations of the CD19+ - and CD3+ -lymphocytes in the acute state of psychosis especially in patients with the paranoid subtype of schizophrenia, and the "normalization" during the observation period are discussed under the aspect of the immune hypothesis of schizophrenia, in particular of the type-1/type-2 imbalance hypothesis.

-G308A tumor necrosis factor alpha functional polymorphism and schizophrenia risk: meta-analysis plus association study

Research on -G308A functional polymorphism in the tumor necrosis factor alpha (TNFalpha) gene as a susceptibility factor for schizophrenia has provided contrasting results in different populations. Therefore we conducted a meta-analysis of the published case-control association studies and a replication study in a large sample. Meta-analyses (total sample: 2512 cases versus 3223 controls) showed that the AA genotype was weakly associated with schizophrenia susceptibility in Caucasoids (Odd Ratio OR=1.65, 95% CI=1.00-2.71 Z=1.98 p=0.05). The replication case-control association study (323 DSM-IV-TR schizophrenia patients and 346 controls) showed that the A allele conferred an increased susceptibility for schizophrenia only in males (OR=1.73, 95% CI=1.07-2.79, p=0.025), and the association became more specific when only patients of the paranoid subtype were compared to the controls (relative risk ratio=3.09, 95% CI=1.28-7.47, p=0.012). The presence of the A allele was also associated with a later age at onset of schizophrenia in the whole sample (F(1,291)=7.094, p=0.008). Our results confirm that TNFalpha A allele could have an effect on vulnerability to schizophrenia but further studies revaluating the role of gender and diagnostic subtypes are necessary to confirm these findings.

Homozygosity of the interleukin-10 receptor 1 G330R allele is associated with schizophrenia

Infections of unknown origin and an altered immune response have been hypothesized to play a role in the pathogenesis of schizophrenia. We have previously identified two single nucleotide polymorphisms (SNPs) of the IL-10 receptor 1 (IL-10R1) causing a substitution of glycine 330 to arginine (G330R) and of serine 138 to glycine (S138G). A possible association between these IL-10R1 variants and schizophrenia has been investigated in the present study. DNA of 101 unrelated Austrian patients with a DSM-III-R (Diagnostic and Statistical Manual of Mental Disorders) consensus diagnosis of schizophrenia (n = 70) or schizoaffective disorder (n = 31) and DNA of 121 German schizophrenic patients (DSM-III-R) was analyzed for the presence of S138G and G330R by allele-specific multiplex PCRs. Data from patients were compared with 250 unrelated, psychiatric healthy controls. No difference in allele frequency was detected between patients and controls (G330R: 34.0% vs. 30.0%, P = 0.208; S138G: 19.7% vs. 16.6%, P = 0.235; by Fisher's exact test). However, there was a significant difference in genotype distribution (wt/wt, wt/mut, mut/mut) for G330R between patients (46.8%, 38.3%, 14.9%) and controls (47.6%, 44.8%, 7.6%; Fisher's test P = 0.032). No such difference was seen for S138G. Our results suggest that homozygosity of the IL-10R1 G330R allele is associated with schizophrenia and may contribute to the expression of disease phenotype in susceptible individuals.

Potential role of lymphotoxin-alpha (tumor necrosis factor-beta) in the development of schizophrenia

Immune hypothesis of schizophrenia fits well with the supposed interaction between genetic and environmental factors in understanding its complicated pathogenesis that is not be able to be explained by any one supposed hypothesis. Prenatal infections have been also suggested to be associated with schizophrenia in which cytokines may play a critical role in the translation of prenatal infection to develop schizophrenia. Moreover, antipsychotics are known to have direct or indirect effects on the immune system. Among cytokines, the immunomodulatory functions of lymphotoxin-alpha (tumor necrosis factor (TNF)-beta) is well known and could come up with the pathophysiology of schizophrenia. It affects and modulates production of other cytokines such as TNF-alpha and IL-6 which are consistently proposed to be involved in the development of schizophrenia. TNF-beta is also crucial to prevent prenatal infections. In addition, TNF-beta is effective in the protection of neuronal cells against glutamate and NMDA toxicity which is considered a neurodevelopmental hypothesis of schizophrenia. Moreover, it was also found to be associated with the regulation of glial cells and stimulation of the synthesis and secretion of nerve growth factors (NGFs) in the CNS. Finally, TNF-beta gene is located on the short arm of chromosome 6 (6p21.1-6p21.3), where is a possible susceptibility locus for schizophrenia. Therefore, TNF-beta may provide a new insight for understanding schizophrenia, providing a more systematic organization of immunological contributing factors to the development of schizophrenia.

Cytokines in schizophrenia and the effects of antipsychotic drugs

Growing evidence suggests that the immune, endocrine, and nervous systems interact with each other through cytokines, hormones, and neurotransmitters. The activation of the cytokine systems may be involved in the neuropathological changes occurring in the central nervous system (CNS) of schizophrenic patients. Numerous studies report that treatment with antipsychotic drugs affects the cytokine network. Hence, it is plausible that the influence of antipsychotics on the cytokine systems may be responsible for their clinical efficacy in schizophrenia. This article reviews current data on the cytokine-modulating potential of antipsychotic drugs. First, basic information on the cytokine networks with special reference to their role in the CNS as well as an up-to-date knowledge of the cytokine alterations in schizophrenia is outlined. Second, the hitherto published studies on the influence of antipsychotics on the cytokine system are reviewed. Third, the possible mechanisms underlying antipsychotics' potential to influence the cytokine networks and the most relevant aspects of this activity are discussed. Finally, limitations of the presented studies and prospects of future research are delineated.

Schizophrenia, autoimmunity and immune system dysregulation: A comprehensive model updated and revisited

Recent investigation suggests a strong relationship between immunological effects and the pathophysiology of schizophrenia. Two prevalent approaches exist to this association. First, is more empirical a-priori research investigating immunological changes prevalent in schizophrenia and the second approach is more hypothesis-driven with analysis of immunological changes in schizophrenia based on known irregularities of the illness. The former approach is based upon three predominant lines of investigation including observations of a diffuse non-specific overactivation of the immunological response system, of a T-helper cell type 1 immune activation and of a T-helper cell type 2 immune activation in subgroups of schizophrenia patients. These last two theories suggest that a subgroup of patients with schizophrenia may demonstrate features of an autoimmune process, a theory supported by a growing database of investigation. The latter approach notes that many observations of immune dysregulation in schizophrenia overlap with central etiopathophysiological mechanisms as well as with clinical manifestations of the illness. Immunotherapy offers the opportunity to modify or re-balance the immune system and may become useful in management of the illness. Given that autoimmune mechanisms could interrupt neurotransmission, any process interfering with this disruption including therapeutic antibodies to involved cytokines, or with various other natural autoantibodies or immune system regulators, may become useful in the augmentative management of the illness.

Neuroimmune-endocrine crosstalk in schizophrenia and mood disorders

This review focuses on possible causes and the impact of different immune states in schizophrenia and major depression. It discusses the fact that, in schizophrenia, an over-activation of the type 2 immune response may dominate, while the type 1 and the pro-inflammatory immune responses are over-activated in major depression. The consequence of these diverse immune states is the activation and, respectively, inhibition of different enzymes in tryptophan/kynurenine metabolism, which may lead to an overemphasis of N-methyl-D-aspartate (NMDA) receptor antagonism in schizophrenia and of NMDA-receptor agonism in depression, resulting in glutamatergic hypofunction in schizophrenia and glutamatergic hyperfunction in major depression. In addition, the activation of the type 1 and the pro-inflammatory immune responses in major depression result in increased serotonin degradation and a serotonergic deficit. While antipsychotics and antidepressants today mainly act on the dopaminergic-glutamatergic and the noradrenergic-serotonergic neurotransmission, anti-inflammatory and immune-modulating therapies might act more basically at the pathophysiological mechanism. The limitations of this concept, however, are critically discussed.

Schizophrenia as an inflammation-mediated dysbalance of glutamatergic neurotransmission

This overview tries to bridge the gap between psychoneuroimmunological findings and recent results from pharmacological, neurochemical and genetic studies in schizophrenia. Schizophrenia is a disorder of dopaminergic neurotransmission, but modulation of the dopaminergic system by glutamatergic neurotransmission seems to play a key role. This view is supported by genetic findings of the neuregulin- and dysbindin genes, which have functional impact on the glutamatergic system. Glutamatergic hypofunction, however, is mediated by the N-methyl-D-aspartate (NMDA)-receptor antagonism. The only endogenous NMDA receptor antagonist identified up to now is kynurenic acid (KYNA). Despite the NMDA receptor antagonism, KYNA also blocks, in lower doses, the nicotinergic acetycholine receptor, i.e., increased KYNA levels can explain psychotic symptoms and cognitive deterioration. KYNA levels are described to be higher in the cerebrospinal fluid (CSF) and in critical central nervous system (CNS) regions of schizophrenics as compared to controls. Another line of evidence suggests that a (prenatal) infection is involved in the pathogenesis of schizophrenia. Due to an early sensitization process of the immune system or to a (chronic) infection, which is not cleared through the immune response, an immune imbalance between the type-1 and the type-2 immune responses takes place in schizophrenia. The type-1 response is partially inhibited, while the type-2 response is over-activated. This immune constellation is associated with inhibition of the enzyme indoleamine dioxygenase (IDO), because IDO - located in astrocytes and microglial cells - is inhibited by type-2 cytokines. IDO catalyzes the first step in tryptophan metabolism, the degradation from tryptophan to kynurenine, as does tryptophan 2,3-dioxygenase (TDO). Due to the inhibition of IDO, tryptophan-kynurenine is predominantly metabolized by TDO, which is located in astrocytes, not in microglial or other CNS cells. In schizophrenia, astrocytes in particular are activated, as increased levels of S100B appear. Additionally, they do not have the enzymatic equipment for the normal metabolism-route of tryptophan. Due to the lack of kynurenine hydroxylase (KYN-OHase) in astrocytes, KYNA accumulates in the CNS, while the metabolic pathway in microglial cells is blocked. Accordingly, an increase of TDO activity has been observed in critical CNS regions of schizophrenics. These mechanisms result in an accumulation of KYNA in critical CNS regions. Thus, the immune-mediated glutamatergic-dopaminergic dysregulation may lead to the clinical symptoms of schizophrenia. Therapeutic consequences, e.g., the use of anti-inflammatory cyclo-oxygenase-2 inhibitors, which can also decrease KYNA directly, are discussed.

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

The alteration of T helper 1 (TH1) and TH2 responses and related cell-mediated immunity has been supposed to be associated with the immunological pathogenesis in the development of schizophrenia. Increasing evidence suggested the alteration of cytokines in accordance with the antipsychotic treatment as well, so that this study aimed at investigating the aberration of TH1 and -2 cytokines before and after antipsychotic treatment in patients with schizophrenia. Thirty-five schizophrenic patients with antipsychotic naïve or free more than 2 months participated in the study. We measured the plasma levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-2 (TH1), and IL-6, IL-10 and IL-13 (TH2) at the time of admission and after an 8-week antipsychotic treatment. The IL-6 (p = 0.001) and -13 (p = 0.004) levels were significantly decreased after antipsychotic treatment than those of before antipsychotic treatment. The total and general PANSS score changes were correlated with the change of IL-6 (r = 0.598, corrected p < 0.05; r = 0.550, corrected p = 0.005, respectively). The baseline IL-6 level was correlated with change of general PANSS score (r = 0.449, corrected p = 0.044), whereas changes of other PANSS scores were not correlated with any other baseline cytokine levels. The baseline total PANSS score was correlated with the baseline levels of IL-13 (r = 0.776, corrected p < 0.005). The baseline total and general PANSS scores were correlated with the baseline levels of IL-6 (r = 0.689, corrected p < 0.005; r = 0.653, corrected p < 0.005). The correlations between the baseline levels of cytokines and the duration of illness and the age at onset were not found. Our study supports that TH-2 arm cytokines may be involved in the improvement of psychopathology and symptomatologies of schizophrenia and that antipsychotic drugs may suppress some TH-2 cytokines in patients with schizophrenia.

COX-2 inhibitors as adjunctive therapy in schizophrenia: rationale for use and evidence to date

A better understanding of the human immune system and its complex interactions has resulted in new insights into the pathoaetiological mechanisms of psychiatric disorders. As a result, new treatment options are being explored. Several findings suggest that an imbalanced immune response is involved in the pathophysiology of schizophrenia. COX-2 inhibitors are known to influence the immune system in a way that may redirect this imbalance. Based on these suggestions, the COX-2 inhibitor celecoxib has been tested as a possible adjunctive therapeutic approach in the treatment of schizophrenia. While the first trial using celecoxib as add-on therapy to an atypical antipsychotic showed a significant beneficial effect, recent studies demonstrated that this effect may be limited to patients with recent-onset schizophrenia.