Cytokine serum levels, autologous mixed lymphocyte reaction and surface marker analysis in never medicated and chronically medicated schizophrenic patients

Stress, schizophrenia and bipolar disorder

The role of stress in precipitating psychotic episodes in schizophrenia and bipolar disorder has long been acknowledged. However, the neurobiological mechanism/s of this association have remained elusive. Current neurodevelopmental models of psychosis implicate early dysfunction in biological systems regulating hypothalamic-pituitary-adrenal axis and immune function, with long-term effects on the development of the brain networks responsible for higher order cognitive processes and stress reactivity in later life. There is also increasing evidence of childhood trauma in psychosis, and its impact on the development of brain systems regulating stress. These findings are emerging in the context of a new era of epigenetic methods facilitating the study of environmental effects on gene expression. The evidence is thus converging: exposure to stress at critical periods in life may be an important factor in the development of the brain dysfunction that represents psychosis vulnerability, rather than merely interacting with an independent 'biological vulnerability' to manifest in psychosis.

Autoimmunity, inflammation, and psychosis: a search for peripheral markers

Accumulating evidence supports the view that deregulation of the immune system represents an important vulnerability factor for psychosis. In a subgroup of psychotic patients, the high comorbidity with autoimmune and chronic inflammatory conditions suggests a common underlying immune abnormality leading to both conditions. The reviewed data of affective and nonaffective psychosis show that if immune biomarkers exist for such immune abnormality, they may be found in raised macrophage/monocyte inflammatory activation patterns (monocytosis, high-inflammatory gene expression, raised glucocorticoid receptor β/glucocorticoid receptor α ratio, and high levels of proinflammatory and anti-inflammatory monocyte/macrophage derived cytokines in serum/plasma), reduced T cell numbers/proliferation, and TH1 skewing. This activation of the inflammatory response system may be suggestive for microglia activation, as these cells are the macrophages of the brain. Indeed, there is some evidence of activation of the microglia as detected in positron emission tomography scans and in histopathology, and it is assumed that this activation disturbs the development and function of neuronal circuits in the brain. Further, animal models of psychotic conditions (maternal stress and inflammation paradigms) suggest that such monocyte/microglia activation could be seen as the result of a combination of genetic predisposition and an immune-mediated two-hit model. Infection but also environmental stressors during gestation/early life activate microglia, perturbing neuronal development, thereby setting the stage for vulnerability for later psychotic disorders. A second hit, such as endocrine changes, stress, or infection, could further activate microglia, leading to functional abnormalities of the neuronal circuitry in the brain and psychosis.

First-episode psychosis: an inflammatory state?

In the last decade an increasing body of research has focussed on the potential role of inflammation in the onset of psychiatric disorders. Although the association between inflammation and depression appears now widely acknowledged, mixed findings have been reported in psychosis leaving the pathophysiological role of inflammation in psychosis still unclear. This paper aims to review studies focussing on inflammation in first-episode psychosis, in order to avoid the possible confounding effects of the long duration of illness and chronic treatment with psychotropic medications. Increased levels of IL-6, TNF-α and IL-1β are the most consistent findings from the studies conducted in first-episode psychosis patients. Mixed findings on other cytokines could be partly due to the different methodologies of the studies reviewed. The findings on the association between inflammatory markers and clinical symptoms and physical health, as well as on the effect of antipsychotic medications on inflammation at the onset of psychosis are also reviewed and discussed. The increased inflammation at onset of psychosis as well as in other psychiatric conditions, such as depression, suggests the presence of biological abnormalities which play a pathophysiological role across different diagnostic categories. Future research should test if increased inflammation could be used for the development of biomarkers, as well as as a potential therapeutic target for different subsamples of patients independently of their diagnostic category.

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).

Evidences for a progressive microglial activation and increase in iNOS expression in rats submitted to a neurodevelopmental model of schizophrenia: reversal by clozapine

Schizophrenia was proposed as a progressive neurodevelopmental disorder. In this regard herein we attempted to determine progressive inflammatory and oxidative alterations induced by a neonatal immune challenge and its possible reversal by clozapine administration. For this end, Wistar rats at postnatal day (PN) 5-7 were administered the viral mimetic polyriboinosinic-polyribocytidilic acid (polyI:C) or saline. A distinct group of animals additionally received the antipsychotic drug clozapine (25mg/kg) from PN60 to 74. At PN35 (periadolescence), 60 (adult) and 74 (adulthood) the animals were submitted to behavioral determinations of prepulse inhibition of the startle (PPI) and Y maze task for working memory evaluation. At PN35 and 74 the animals were sacrificed and the hippocampus (HC), prefrontal cortex (PFC) and striatum (ST) immunostained for Iba-1, a microglial marker, and inducible nitric oxide synthase (iNOS). At PN74 oxidative stress parameters, such as, reduced glutathione levels (GSH) and lipid peroxidation were determined. The results showed a progressive increase of microglial activation and iNOS immunostaining from PN35 to PN74 mainly in the CA2 and CA3 regions of the HC and in the ST. At PN74 neonatal challenge also induced an oxidative imbalance. These inflammatory alterations were accompanied by deficits in PPI and working memory only in adult life that were reversed by clozapine. Clozapine administration reversed microglial activation and iNOS increase, but not the alterations of oxidative stress parameters. Taken together these results give further evidences for a neuroprogressive etiology and course of schizophrenia and that clozapine may partly alleviate this process.

Association between antibodies to multiple infectious and food antigens and new onset schizophrenia among US military personnel

INTRODUCTION

Multiple studies have documented immune activation in many individuals with schizophrenia suggesting that antigens capable of generating a prolonged immune response may be important environmental factors in many cases of this disorder. While existing studies have found single-agent associations of antibodies to food and neurotropic infectious agents with schizophrenia, a simultaneous examination of multiple agents may shed light on agent interactions or possible etiopathogenic pathways.

METHODS

We used traditional regression and novel statistical techniques to examine associations of single and combined infectious and food antigens with schizophrenia. We tested 6106 serum samples from 855 cases and 1165 matched controls.

RESULTS

Higher antibody levels to casein were borderline significant in the prediction of schizophrenia (HR=1.08, p=0.06). Study participants with higher cytomegalovirus (CMV) IgG antibody levels had a reduced risk of developing schizophrenia (HR=0.90; p=0.02). While IgG antibodies to gliadin, Toxoplasma gondii, vaccinia, measles, and human herpesvirus-6 (HHV-6) showed no significant independent associations with schizophrenia, the increase in antibody levels to several combinations of agents, to include casein, measles, CMV, T. gondii and vaccinia, was predictive of an 18-34% increase in the risk of developing schizophrenia.

CONCLUSION

Certain patterns of antibodies, involving some agents, were predictive of developing schizophrenia, with the magnitude of association rising when the level of antibodies increased to two or more agents. A heightened antibody response to a combination of several infectious/food antigens might be an indicator of an altered immune response to antigenic stimuli.

A gender-specific association of interleukin 1 receptor antagonist polymorphism with schizophrenia susceptibility

OBJECTIVE

Recent genetic studies have revealed that the interleukin (IL) 1 gene complex is associated with schizophrenia in the Caucasian population; however, data from the North African population are limited. To further assess the role of interleukin 1 receptor antagonist protein (IL1Ra) in schizophrenia, we examined a functional multiallelic polymorphism localised in intron 2 of this receptor gene associated with an altered level of IL1Ra.

METHODS

In the present case-control study, we have analysed the (86 bp) n polymorphism of the interleukin 1 receptor antagonist (IL1RN) gene (RS 1794068) by polymerase chain reaction genotyping in 259 patients with schizophrenia and 178 healthy controls from the Tunisian population.

RESULTS

We showed that the frequencies of the IL1RN*2/2 genotype and allele 2 were higher in the patient group compared with the control group, and the difference was statistically significant [13.5% vs. 5.6%, p = 10-3, odds ratio (OR) = 3.2% and 32.8% vs. 21.9%, p = 3 × 10-4, OR = 1.76, respectively). When we evaluated the association between this genetic polymorphism and the clinical variables of schizophrenia, we found that the frequencies of the 2/2 genotype and allele 2 were significantly higher in the male patient group (p = 10-4 and 10-5, respectively) compared with the male control group, indicating a substantially increased risk for sex-onset schizophrenia with inheritance of the IL1RN2 allele. When the association between the genotypes and outcome was evaluated by multiple logistic regression analysis, the adjusted OR for the IL1RN genotypes remained statistically significant [1.39; 95% confidence interval (CI) = 1.11-1.73; p = 0.003].

CONCLUSION

The intron 2 polymorphism in IL1RN or a genetic polymorphism at proximity seems to be associated specifically with schizophrenia in the Tunisian male population.

The therapeutic role of interleukin-10 after spinal cord injury

Spinal cord injury (SCI) is a devastating condition affecting 270,000 people in the United States. A potential treatment for decreasing the secondary inflammation, excitotoxic damage, and neuronal apoptosis associated with SCI, is the anti-inflammatory cytokine interleukin-10. The best characterized effects of IL-10 are anti-inflammatory-it downregulates pro-inflammatory species interleukin-1β (IL-1β), interleukin-2 (IL-2), interleukin-6 (IL-6), tumor necrosis factor-α, interferon-γ, matrix metalloproteinase-9, nitric oxide synthase, myeloperoxidase, and reactive oxygen species. Pro-apoptotic factors cytochrome c, caspase 3, and Bax are downregulated by IL-10, whereas anti-apoptotic factors B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X, B-cell lymphoma-extra large (Bcl-xl) are upregulated by IL-10. IL-10 also provides trophic support to neurons through the IL-10 receptor. Increased tissue sparing, functional recovery, and neuroprotection are seen with an immediate post-SCI systemic administration of IL-10. Treatment of SCI with IL-10 has been used successfully in combination with Schwann cell and olfactory glial cell grafts, as well as methylprednisolone. Minocycline, tetramethylpyrazine, and hyperbaric oxygen treatment all increase IL-10 levels in a SCI models and result in increased tissue sparing and functional recovery. A chronic systemic administration of IL-10 does not appear to be beneficial to SCI recovery and causes increased susceptibility to septicemia, pneumonia, and peripheral neuropathy. However, a localized upregulation of IL-10 has been shown to be beneficial and can be achieved by herpes simplex virus gene therapy, injection of poliovirus replicons, or surgical placement of a slow-release compound. IL-10 shows promise as a treatment for SCI, although research on local IL-10 delivery timeline and dosage needs to be expanded.

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.

Different changes in cortical tumor necrosis factor-α-related pathways in schizophrenia and mood disorders

The growing body of evidence implicating tumor necrosis factor-α (TNFα) in the pathophysiology of psychiatric disorders led us to measure levels of that protein in the cortex of subjects with major depressive disorders (MDD). Having reported an increase (458%) in the levels of the transmembrane (tmTNFα), but not the soluble (sTNFα), form of the protein in Brodmann's area (BA) 46, but not 24, in people with the disorder, we decided to examine additional components of TNFα-related pathways in the same regions in people with MDD and extend our studies to the same cortical regions of people with schizophrenia (Sz) and bipolar disorders (BD). Using postmortem tissue, western blots and quantitative PCR, we have now shown there is a significant increase (305%) in tmTNFα in Brodmann's area 24, but not 46, from subjects with BD, and that levels of the protein were not altered in Sz. Levels of sTNFα were not altered in BD or Sz. In addition, we have shown that levels of TNF receptor 1 (TNFR1) mRNA are increased in BA 24 (53%) and BA 46 (82%) in people with Sz, whereas levels of TNFR2 mRNA was decreased in BA 46 in people with mood disorders (MDD=-51%; BD=-67%). Levels of proteins frequently used as surrogate markers of neuronal, astrocytic and microglia numbers, as well as levels of the pro-inflammatory marker (interleukin 1β), were not changed in the cortex of people with mood disorders. Our data suggest there are differential changes in TNFα-related markers in the cortex of people with MDD, BD and Sz that may not be related to classical inflammation and may cause changes in different TNFα-related signaling pathways.

Serum and gene expression profile of cytokines in first-episode psychosis

An inflammatory syndrome has been previously reported in chronic schizophrenia. The aims of this study were to investigate: (1) serum levels and leukocyte gene expression of cytokines in patients with first-episode psychosis and controls; and (2) possible causes of abnormal cytokine levels in first-episode psychosis, testing their association with psychosocial stressors, current nicotine and cannabis use, and duration of antipsychotic treatment. We recruited 24 first-episode psychosis patients and 24 healthy controls matched for age, gender, ethnicity and body mass index. Serum interleukin(IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, Tumour Necrosis Factor- α (TNF-α), Interferon- γ (IFN-γ), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and monocyte chemotactic protein-1 (MCP-1) were analysed in all subjects. Leukocyte gene expression analyses were conducted only for those cytokines that were different between-groups in the serum analyses. Patients had significantly higher serum levels of IL-1α (effect size d=0.6, p=0.03), IL-1β (d=0.4, p=0.01), IL-8 (d=0.6, p=0.01) and TNF-α (d=0.7, p=0.05) and a trend for higher IL-6 serum levels (d=0.3, p=0.09) when compared with controls. Leukocyte m-RNA levels of IL-1α (d=0.6, p=0.04), IL-6 (d=0.7, p=0.01) and TNF-α (d=1.6, p<0.001), but not IL-1β and IL-8, were also significantly higher in patients. A history of childhood trauma was associated with higher TNF-α serum levels (p=0.01), while more recent stressful life-events were associated with higher TNF-α mRNA levels in leukocytes (p=0.002). In conclusion, first-episode psychosis is characterised by a pro-inflammatory state supported, at least in part, by activation of leukocytes. Past and recent stressors contribute to this pro-inflammatory state.

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

BACKGROUND

Schizophrenia is associated with immune system dysfunction, including abnormal blood immune cell parameters. We performed a meta-analysis of these associations, considering the effect of clinical status and antipsychotic treatment following an acute exacerbation of psychosis.

METHODS

We identified articles by searching PubMed, PsycINFO, and Thomson Reuters (formerly ISI) Web of Knowledge and the reference lists of identified studies.

RESULTS

Sixteen studies of blood lymphocytes met the inclusion criteria. There was insufficient data for a meta-analysis of the mononuclear phagocytic system. In cross-sectional studies, there was a significant increase in the CD4% and CD56% in acutely relapsed inpatients. Absolute levels of total lymphocytes, CD3, and CD4, and the CD4/CD8 ratio were significantly increased, and the CD3% was significantly decreased in drug-native first-episode psychosis. In longitudinal studies, the CD4/CD8 ratio appeared to be state-related markers, as it decreased following antipsychotic treatment for acute exacerbations of psychosis. Absolute CD56 levels appeared to be a trait marker, as levels significantly increased following antipsychotic treatment for relapse.

CONCLUSIONS

Blood lymphocyte abnormalities in drug-naïve first-episode psychosis suggest an effect that may be independent of antipsychotic medications. While some parameters (CD4/CD8) may be state markers for acute exacerbations of psychosis, others (CD56) may be trait markers; however, more longitudinal studies are needed. Although these findings could provide the basis for future hypothesis testing, a relatively small number of studies and subjects, lack of correlative data with clinical features, and inadequate consideration of potential confounding factors limit the results.

Increased inflammatory markers identified in the dorsolateral prefrontal cortex of individuals with schizophrenia

Upregulation of the immune response may be involved in the pathogenesis of schizophrenia with changes occurring in both peripheral blood and brain tissue. To date, microarray technology has provided a limited view of specific inflammatory transcripts in brain perhaps due to sensitivity issues. Here we used SOLiD Next Generation Sequencing to quantify neuroimmune mRNA expression levels in the dorsolateral prefrontal cortex of 20 individuals with schizophrenia and their matched controls. We detected 798 differentially regulated transcripts present in people with schizophrenia compared with controls. Ingenuity pathway analysis identified the inflammatory response as a key change. Using quantitative real-time PCR we confirmed the changes in candidate cytokines and immune modulators, including interleukin (IL)-6, IL-8, IL-1β and SERPINA3. The density of major histocompatibility complex-II-positive cells morphologically resembling microglia was significantly increased in schizophrenia and correlated with IL-1β expression. A group of individuals, most of whom had schizophrenia, were found to have increased inflammatory mRNA expression. In summary, we have demonstrated changes in an inflammatory response pathway that are present in ∼40% of people diagnosed with schizophrenia. This suggests that therapies aimed at immune system attenuation in schizophrenia may be of direct benefit in the brain.

Explorando o componente inflamatório da esquizofrenia

A esquizofrenia é uma doença heterogênea caracterizada por um conjunto de manifestações clínicas. Um grande número de estudos ao longo dos últimos 20 anos apontou para anormalidades no sistema imune em pacientes que sofrem dessa condição. Em adição, tem sido mostrado que a psicose e a disfunção cognitiva associadas com a esquizofrenia estão ligadas a doenças autoimunes. Aqui, revisamos a evidência que sugere que um status pró-inflamatório do sistema imune induz sintomas psicopatológicos e pode estar envolvido na fisiopatologia dessa principal doença mental. Também propomos que futuros estudos pré-clínicos e clínicos deveriam levar em conta tais causas predefinidas e o status do componente inflamatório. Estratificação de pacientes e estratégias de medicina personalizadas baseadas no direcionamento ao componente inflamatório da doença poderiam ajudar na redução de sintomas e da progressão da doença. Por fim, isso poderia levar a novos conceitos na identificação de alvos moleculares em esquizofrenia e estratégias de descoberta de drogas.

Effect of the interleukin-1β gene on dorsolateral prefrontal cortex function in schizophrenia: a genetic neuroimaging study

BACKGROUND

Genetic studies have found that the interleukin-1β gene (IL1B, 2q13) influences the risk for schizophrenia, but the underlying biological mechanisms of the association are still unclear. Investigation of the effects of genetic variability in this gene on brain function could provide more information about its role in the disorder.

METHODS

The present study examined the effects of a functional polymorphism at IL1B gene promoter (-511C/T; rs16944) on brain correlates of working memory performance in schizophrenia. Forty-eight schizophrenia patients and 46 control subjects underwent functional magnetic resonance imaging while performing the n-back task.

RESULTS

In the pooled sample, genetic variability at this locus was associated with differential brain activation in a bilateral frontal region including the dorsolateral prefrontal cortex. There was also a significant diagnosis × genotype interaction effect in an overlapping frontal region: the IL1B polymorphism did not affect activation in the control subjects in this area, but the schizophrenia patients who were T carriers showed significantly higher activation than the CC homozygotes.

CONCLUSIONS

The findings support a role for IL1B variability in the dorsolateral prefrontal cortex dysfunction classically associated with schizophrenia.

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.

A Review of Brain-derived Neurotrophic Factor as a Candidate Biomarker in Schizophrenia

Brain-derived neurotrophic factor (BDNF), a neurotrophin known to be responsible for development, regeneration, survival and maintenance of neurons has been implicated in the pathophysiology of schizophrenia. This review seeks to complement previous reviews on biological roles of BDNF and summarizes evidence on the involvement of BDNF in the pathophysiology of schizophrenia with an emphasis on clinical relevance. The expressions of BDNF were altered in patients with schizophrenia and were found to be correlated with psychotic symptomatology. Antipsychotics appeared to have differential effects on expression of BDNF but did not restore BDNF expression of patients with schizophrenia to normal levels. In addition, evidence suggests that BDNF is involved in the major neurotransmitter systems and is associated with disruptions in brain structure, neurodevelopmental process, cognitive function, metabolic and immune systems commonly associated with schizophrenia. Besides that, BDNF has been demonstrated to be tightly regulated with estrogen which has also been previously implicated in schizophrenia. Evidence gathered in this review confirms the relevance of BDNF in the pathophysiology of schizophrenia and the potential utility of BDNF as a suitable biomarker for diagnostic and prognostic purposes for disease outcome and other co-morbidities. However, further investigations are warranted to examine the specificity of BDNF in schizophrenia compared to other neurodegenerative disorders and other neuropsychiatric illness. Longitudinal prospective studies will also be of added advantage for evaluation of prognostic utility of BDNF in schizophrenia.

The immune theory of psychiatric diseases: a key role for activated microglia and circulating monocytes

This review describes a key role for mononuclear phagocytes in the pathogenesis of major psychiatric disorders. There is accumulating evidence for activation of microglia (histopathology and PET scans) and circulating monocytes (enhanced gene expression of immune genes, an overproduction of monocyte/macrophage-related cytokines) in patients with bipolar disorder, major depressive disorder, and schizophrenia. These data are strengthened by observations in animal models, such as the MIA models, the chronic stress models, and the NOD mouse model. In these animal models of depressive-, anxiety-, and schizophrenia-like behavior, similar activations of microglia and circulating monocytes can be found. These animal models also make in-depth pathogenic studies possible and show that microglia activation impacts neuronal development and function in brain areas congruent with the altered depressive and schizophrenia-like behaviors.

Cytokines in schizophrenia: possible role of anti-inflammatory medications in clinical and preclinical stages

AIMS

In this paper, we review the literature on the efficacy of anti-inflammatory agents as neuroprotectors in clinical and preclinical stages of schizophrenia.

METHOD

A synthetic and integrative approach was applied to review studies stemming from epidemiology, phenomenology, cognition, genetics and neuroimaging data. We provide conclusions and future directions of research on early-onset schizophrenia.

RESULTS

Abnormal inflammatory activation has been demonstrated in schizophrenia. Increases or imbalances in cytokines before birth or during childhood may impact neurodevelopment and produce vulnerability to schizophrenia. The specificity of inflammatory abnormalities in psychiatric disorders is controversial. Similar increases in pro-inflammatory cytokines have been described in other disorders, especially mood and anxiety disorders. One of the most important challenges at this point is the understanding of neurobiological correlates of prodromal stages of schizophrenia.

CONCLUSION

Although future research should investigate the exact role of different cytokines in pathophysiology of schizophrenia, these mediators emerge as promising molecular targets to its prevention and treatment.

Immunomodulation in schizophrenia: A study among the Indian schizophrenia patients of Siliguri, West Bengal

Authors investigated the circumstantial evidence for autoimmunity in schizophrenia patients of Siliguri by considering the immune parameters like HLA Class I genes, IL-2 and IL6 and T cell subsets. Low resolution PCR-SSP method was applied for typing the HLA genes. Serum levels of IL-2 and IL-6 were measured by ELISA method. The CD4+ and CD8+ subset count were done using flow cytometry. A significant increase in HLA A*03 gene was observed in patients along with the significant decrease of HLA-A*31 and HLA-B*51. Both IL-2 and IL-6 were found to have decreased levels in the patients. Although the mean percentage of CD4+ and CD8+ cells was higher in patients but not significantly higher than controls. These cumulative preliminary findings are suggestive of alterations in the immune system of schizophrenia patients of this region.

Anti-inflammatory signaling in schizophrenia

A great deal of interest has been centered upon activated inflammatory processes in schizophrenia and their contribution to disease-relevant brain and behavioral impairment. In contrast, the role of anti-inflammatory signaling has attracted somewhat less attention in this context. The present article focuses on the emerging role of anti-inflammatory signaling in schizophrenia and discusses the potential influence of altered anti-inflammatory activity on progressive inflammatory processes, physical and metabolic functions, and treatment effects related to the use of conventional antipsychotic drugs and immunomodulatory agents in the pharmacotherapy of schizophrenia. By reviewing existing evidence, it appears that enhanced anti-inflammatory activity has many faces in schizophrenia: On the one hand, it may effectively limit potentially harmful inflammatory processes and may contribute to the improvement of psychopathological symptoms, especially when the anti-inflammatory system is boosted at early stages of the disease. On the other hand, enhanced anti-inflammatory activity may render affected individuals more susceptible to distinct physiological abnormalities such as cardiovascular disease, and may further impede the resistance to specific infectious agents. Therefore, an enhancement of anti-inflammatory signaling in schizophrenia might not simply be said to be either advantageous or disadvantageous, but rather should be interpreted and dealt with in a context-dependent manner. Increased awareness of the multiple roles of anti-inflammatory signaling may readily help to reduce additional health burdens in schizophrenia, and at the same time, may provide opportunities to further explore the benefits associated with anti-inflammatory strategies in the symptomatological and/or preventive treatment of this disorder.

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.

The role of NGF and IL-2 serum level in assisting the diagnosis in first episode schizophrenia

Development of reliable diagnostic bio-markers for schizophrenia remains a diagnostic challenge. Serum NGF and IL-2 were analyzed to examine the diagnostic efficiency and predictive capability of these two biomarkers in relation to schizophrenia diagnosis. Thirty neuroleptic naïve subjects with first-episode schizophrenia, thirty patients with major depressive disorder (MDD) and twenty-eight healthy control subjects participated in the study. One-way ANOVA demonstrated significantly lower serum IL-2 and NGF among schizophrenic patients and patients with MDD compared with healthy controls. Receiver operating characteristic (ROC) curve analysis was used to ascertain diagnostic efficiency of serum IL-2 and NGF levels. Area under the ROC curve (AUC) revealed a high level of differentiation between schizophrenic patients and healthy controls for both IL-2 and NGF serum concentrations. Diagnostic efficiency of combined NGF and IL-2 serum levels was also high in schizophrenic patients compared with healthy controls. Serum NGF and IL-2 are promising as potential screening or diagnostic biomarkers for schizophrenia and may be a useful adjunct for clinical assessment.

Functional characterization of the complement receptor type 1 and its circulating ligands in patients with schizophrenia

BACKGROUND

Whereas the complement system alterations contribute to schizophrenia, complement receptors and regulators are little studied. We investigated complement receptor type 1 (CR1) expression on blood cells, the levels of circulating immune complexes (CIC) containing ligands of CR1, C1q complement protein and fragments of C3 complement protein (C1q-CIC, C3d-CIC), and CR1 C5507G functional polymorphism in schizophrenia patients and controls.

RESULTS

We found an increased C1q-CIC level and CR1 expression on blood cells, elevated number of CR1 positive erythrocytes and reduced number of CR1 positive lymphocytes and monocytes in patients compared to controls. No difference in the levels of C3d-CIC between groups was observed. Higher CR1 expression on erythrocytes in CC genotype versus CG+GG for both groups was detected, whereas no difference was observed for other cell populations. Our results indicated that schizophrenia is associated with the increased CR1 expression and C1q-CIC level.

CONCLUSIONS

Our study for the first time indicated that schizophrenia is associated with the increased CR1 expression and C1q-CIC level. Further studies in other ethnic groups are needed to replicate these findings.

Inflammatory processes in schizophrenia: a promising neuroimmunological target for the treatment of negative/cognitive symptoms and beyond

Emerging evidence indicates that schizophrenia is associated with activated peripheral and central inflammatory responses. Such inflammatory processes seem to be influenced by a number of environmental and genetic predisposition factors, and they may critically depend on and contribute to the progressive nature of schizophrenic disease. There is also appreciable evidence to suggest that activated inflammatory responses can undermine disease-relevant affective, emotional, social, and cognitive functions, so that inflammatory processes may be particularly relevant for the precipitation of negative and cognitive symptoms of schizophrenia. Recent clinical trials of anti-inflammatory pharmacotherapy in this disorder provide promising results by showing superior beneficial treatment effects when standard antipsychotic drugs are co-administered with anti-inflammatory compounds, as compared with treatment outcomes using antipsychotic drugs alone. Given the limited efficacy of currently available antipsychotic drugs to ameliorate negative and cognitive symptoms, the further exploration of inflammatory mechanisms and anti-inflammatory strategies may open fruitful new avenues for improved treatment of symptoms undermining affective, emotional, social and cognitive functions pertinent to schizophrenic disease.

Expression of anti-cardiolipin antibodies and inflammatory associated factors in patients with schizophrenia

Numerous studies have implicated a connection between schizophrenia and autoimmune disorders. However, the precise relationship and underlying mechanism are still obscure. To further identify the association between autoimmune disorders and schizophrenia, the mRNA expressions of various cytokines and Toll-like receptors (TLRs) in monocytes are examined by using RT-PCR. Additionally, ELISA and zymography were performed to determine the anti-cardiolipin antibody (aCL) and MMP9 activity in serum form schizophrenic patients. Notably, significantly increased interleukin (IL)-6 and IL-10 mRNA were observed in schizophrenic patients, whereas significant reductions of TLR-3 and TLR-5 mRNA were detected. Moreover, significantly increased levels of aCL antibody and a higher frequency of positive-MMP9 activity were detected in serum from patients with schizophrenia. Meanwhile, no significant association was found between each of the medications and aCL activity. These findings demonstrated autoimmune-related phenomena in schizophrenic patients and further suggested a connection between schizophrenia and autoimmune disorders.

Schizophrenia: a pathogenetic autoimmune disease caused by viruses and pathogens and dependent on genes

Many genes have been implicated in schizophrenia as have viral prenatal or adult infections and toxoplasmosis or Lyme disease. Several autoantigens also target key pathology-related proteins. These factors are interrelated. Susceptibility genes encode for proteins homologous to those of the pathogens while the autoantigens are homologous to pathogens' proteins, suggesting that the risk-promoting effects of genes and risk factors are conditional upon each other, and dependent upon protein matching between pathogen and susceptibility gene products. Pathogens' proteins may act as dummy ligands, decoy receptors, or via interactome interference. Many such proteins are immunogenic suggesting that antibody mediated knockdown of multiple schizophrenia gene products could contribute to the disease, explaining the immune activation in the brain and lymphocytes in schizophrenia, and the preponderance of immune-related gene variants in the schizophrenia genome. Schizophrenia may thus be a “pathogenetic” autoimmune disorder, caused by pathogens, genes, and the immune system acting together, and perhaps preventable by pathogen elimination, or curable by the removal of culpable antibodies and antigens.

Dysregulation of chemo-cytokine production in schizophrenic patients versus healthy controls

Background

The exact cause of schizophrenia is not known, although several aetiological theories have been proposed for the disease, including developmental or neurodegenerative processes, neurotransmitter abnormalities, viral infection and immune dysfunction or autoimmune mechanisms. Growing evidence suggests that specific cytokines and chemokines play a role in signalling the brain to produce neurochemical, neuroendocrine, neuroimmune and behavioural changes. A relationship between inflammation and schizophrenia was supported by abnormal cytokines production, abnormal concentrations of cytokines and cytokine receptors in the blood and cerebrospinal fluid in schizophrenia. Since the neuropathology of schizophrenia has recently been reported to be closely associated with microglial activation we aimed to determined whether spontaneous or LPS-induced peripheral blood mononuclear cell chemokines and cytokines production is dysregulated in schizophrenic patients compared to healthy subjects. We enrolled 51 untreated first-episode schizophrenics (SC) and 40 healthy subjects (HC) and the levels of MCP-1, MIP-1α, IL-8, IL-18, IFN-γ and RANTES were determined by Elisa method in cell-free supernatants of PBMC cultures.

Results

In the simultaneous quantification we found significantly higher levels of constitutively and LPS-induced MCP-1, MIP-1α, IL-8 and IL-18, and lower RANTES and IFNγ levels released by PBMC of SC patients compared with HC. In ten SC patients receiving therapy with risperidone, olanzapine or clozapine basal and LPS-induced production of RANTES and IL-18 was increased, while both basal and LPS-induced MCP-1 production was decreased. No statistically significant differences were detected in serum levels after therapy.

Conclusion

The observation that in schizophrenic patients the PBMC production of selected chemo-cytokines is dysregulated reinforces the hypothesis that the peripheral cyto-chemokine network is involved in the pathophysiology of schizophrenia. These preliminary, but promising data are supportive of the application of wider profiling approaches to the identification of biomarker as diagnostic tools for the analysis of psychiatric diseases.

Recent advances in psychoneuroimmunology: Inflammation in psychiatric disorders

Psychiatric disorders are common and complex and their precise biological underpinnings remain elusive. Multiple epidemiological, molecular, genetic and gene expression studies suggest that immune system dysfunction may contribute to the risk for developing psychiatric disorders including schizophrenia, bipolar disorder, and major depressive disorder. However, the precise mechanisms by which inflammation-related events confer such risk are unclear. In this review, we examine the peripheral and central evidence for inflammation in psychiatric disorders and the potential molecular mechanisms implicated including inhibition of neurogenesis, apoptosis, the HPA-axis, the role of brain-derived neurotrophic factor and the interplay between the glutamatergic, dopaminergic and serotonergic neurotransmitter systems.

Immune and neuroimmune alterations in mood disorders and schizophrenia

A large number of publications over the past 20 years have indicated that immune system function is altered in schizophrenia and mood disorder patients. This chapter reviews the evidence, which suggests that a proinflammatory state of the cytokine network induces psychopathologic symptoms and may be involved in the pathogenesis and pathophysiology of these major mental illnesses. The authors also present recent data, which relates immune activation to present theories on the influence of activated immune cells in altering brain function. They also focus on the role of the environment in immune activation and on the role of the microbiome and gut flora. Increased understanding of such factors could help in the development of novel treatment strategies and improved clinical management of mental disorders.

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.

A new nosology of psychosis and the pharmacological basis of affective and negative symptom dimensions in schizophrenia

Although first rank symptoms focus on positive symptoms of psychosis they are shared by a number of psychiatric conditions. The difficulty in differentiating bipolar disorder from schizophrenia with affective features has led to a third category of patients often loosely labeled as schizoaffective. Research in schizophrenia has attempted to render the presence or absence of negative symptoms and their relation to etiology and prognosis more explicit. A dichotomous population is a recurring theme in experimental paradigms. Thus, schizophrenia is defined as process or reactive, deficit or non-deficit and by the presence or absence of affective symptoms. Laboratory tests confirm the clinical impression showing conflicting responses to dexamethasone suppression and clearly defined differences in autonomic responsiveness, but their patho-physiological significance eludes mainstream theory. Added to this is the difficulty in agreeing to what exactly constitutes useful clinical features differentiating, for example, negative symptoms of a true deficit syndrome from features of depression. Two recent papers proposed that the general and specific cognitive features of schizophrenia and major depression result from a monoamine-cholinergic imbalance, the former due to a relative muscarinic receptor hypofunction and the latter, in contrast, to a muscarinic hypersensitivity exacerbated by monoamine depletion. Further development of these ideas will provide pharmacological principles for what is currently an incomplete and largely, descriptive nosology of psychosis. It will propose a dimensional view of affective and negative symptoms based on relative muscarinic integrity and is supported by several exciting intracellular signaling and gene expression studies. Bipolar disorder manifests both muscarinic and dopaminergic hypersensitivity. The greater the imbalance between these two receptor signaling systems, the more the clinical picture will resemble schizophrenia with bizarre, incongruent delusions and increasingly disorganized thought. The capacity for affective expression, by definition a non-deficit syndrome, will remain contingent on the degree of preservation of muscarinic signaling, which itself may be unstable and vary between trait and state examinations. At the extreme end of muscarinic impairment, a deficit schizophrenia subpopulation is proposed with a primary and fixed muscarinic receptor hypofunction.

The genomic profile of bipolar disorder and schizophrenia overlap and both have a common dopaminergic intracellular signaling which is hypersensitive to various stressors. It is proposed that the concomitant muscarinic receptor upregulation differentiates the syndromes, being marked in bipolar disorder and rather less so in schizophrenia. From a behavioral point of view non-deficit syndromes and bipolar disorder appear most proximate and could be reclassified as a spectrum of affective psychosis or schizoaffective disorders. Because of a profound malfunction of the muscarinic receptor, the deficit subgroup cannot express a comparable stress response. Nonetheless, a convergent principle of psychotic features across psychiatric disorders is a relative monoaminergic-muscarinic imbalance in signal transduction.

The mononuclear phagocyte system and its cytokine inflammatory networks in schizophrenia and bipolar disorder

This review describes patients with schizophrenia and bipolar disorder. In such patients, a high inflammatory set point of circulating monocytes at the transcriptome level is observed, involving various inflammatory transcripts forming distinct fingerprints (the transcriptomic monocyte fingerprint in schizophrenia overlaps with that in bipolar disorder, but also differs with it at points). There are increased levels of compounds of the IL-1, IL-6 and TNF system in the serum (be it modest and inconsistent). There is also evidence that the IL-2 system is activated in patients with schizophrenia (and perhaps those with mania), although independently of the activation of the IL-1, IL-6 and TNF systems, suggesting separate inducing mechanisms for monocyte and T-cell activation. It is not yet known whether such T cell activation involves the Th1/Th2/Th17 or Treg systems.

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.

Lower serum cytokine levels in smokers than nonsmokers with chronic schizophrenia on long-term treatment with antipsychotics

OBJECTIVE

Schizophrenia is associated with various abnormalities in the immune system. Suppression of inflammatory cytokines by cigarette smoke is well-established. The purpose of this study was to determine any differences in cytokine profiles in smokers and nonsmokers with schizophrenia and whether there were any relationships among altered cytokine profiles and psychopathological symptoms.

MATERIALS AND METHODS

Serum interleukin (IL)-2, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha levels were measured in 96 male inpatients with DSM-IV schizophrenia: 66 smokers and 30 nonsmokers. Symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS).

RESULTS

The positive PANSS symptoms were lower in smokers than nonsmokers, while the negative symptoms were lower in those who smoked more cigarettes. Cytokine levels were positively correlated: IL-2 level with IL-6 and IL-6 with both IL-8 and TNF-alpha. Both IL-2 and IL-6, but not IL-8 or TNF-alpha, were significantly lower in smokers than nonsmokers (p < 0.002; p < 0.01). Lower IL-2 levels correlated with fewer negative symptoms and with smoking more cigarettes.

CONCLUSIONS

The fewer positive symptoms in smokers and fewer negative symptoms in those who smoked more cigarettes may be associated with nicotine-induced suppression of some inflammatory cytokines.

S100B secretion is stimulated by IL-1beta in glial cultures and hippocampal slices of rats: Likely involvement of MAPK pathway

S100B is an astrocyte-derived cytokine implicated in the IL-1beta-triggered cytokine cycle in Alzheimer's disease. However, the secretion of S100B following stimulation by IL-1beta has not been directly demonstrated. We investigated S100B secretion in cortical primary astrocyte cultures, C6 glioma cells and acute hippocampal slices exposed to IL-1beta. S100B secretion was induced by IL-1beta in all preparations, involving MAPK pathway and, apparently, NF-small ka, CyrillicB signaling. Astrocytes and C6 cells exhibited different sensitivities to IL-1beta. These results suggest that IL-1beta-induced S100B secretion is a component of the neuroinflammatory response, which would support the involvement of S100B in the genesis of neurodegenerative diseases.

Association study of CSF2RB with schizophrenia in Irish family and case - control samples

Colony stimulating factor 2 receptor, beta (CSF2RB) is the shared subunit of receptors for interleukin 3 (IL3), colony stimulating factor 2 (CSF2) and IL5, and is responsible for the initiation of signal transduction triggered by ligand binding. In our previous study, we showed the evidence that the IL3 gene is associated with schizophrenia and the associations observed are sex-specific and dependent on family history (FH). In this article, we studied 10 single-nucleotide polymorphisms in the CSF2RB gene in the Irish Study of High-Density Schizophrenia Families (ISHDSF) and the Irish Case - Control Study of Schizophrenia (ICCSS), and tested allele and haplotype associations with schizophrenia. Using the pedigree disequilibrium test, we found that two markers (rs11705394 and rs7285064) reached nominal significance. In sex-stratified analyses, for both the markers the association signals were mainly derived from male subjects. In the ICCSS sample, we found that several markers (rs2072707, rs2284031 and rs909486) showed sex-specific and FH-dependent associations with schizophrenia. In multimarker haplotype analyses, both ISHDSF and ICCSS samples showed globally significant associations in multiple linkage disequilibrium (LD) blocks sharing minimal LD. Since CSF2RB is essential for IL3 signaling, the findings that both IL3 and CSF2RB showed sex-specific and FH-dependent associations suggest that the IL3 pathway is involved in schizophrenia.

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.

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.

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.

Increased alpha-defensins as a blood marker for schizophrenia susceptibility

Schizophrenia is a severe psychotic illness affecting 1% of the general population. There are no consistent pathological features, and the disorder is defined by a complex symptomatology, which overlaps with other psychiatric illnesses. Diagnosis is based on a clinical interview, relying on the patient meeting criteria according to diagnosis manuals, including Diagnostic and Statistical Manual of Mental Disorders, 4th Ed. and International Statistical Classification of Diseases, 10th Revision. Because of the ambiguous symptoms, the diagnostic process can take many months and often years. Rapid and effective treatment has been shown to impact positively on disease progression and outcome, and it is therefore important to identify disease-associated biomarkers allowing early diagnosis. Reliable biomarkers can be used for the development of diagnostic tests and may also help us understand the underlying pathology of this disorder. In the present study, proteins from anti-CD3 stimulated and unstimulated peripheral blood T cell lysates from 15 minimally medicated and unmedicated patients and 15 age-, sex-, race-, and smoking-matched controls were profiled on cation exchange (CM10) chips using SELDI-TOF. Partial least squares discriminate analysis was used to separate patient and control groups according to the expression of 108 detected peaks, and two peaks of 3,374 and 3,450 Da, corresponding to alpha-defensins based on masses and cationic properties, were found to contribute significantly to the separation of patient and control groups. Reduction of T cell lysates with DTT resulted in a 6-Da shift in the mass of these peaks consistent with the presence of three cysteine bonds in the structure, confirming them as alpha-defensins. Quantification of alpha-defensins in T cell lysates from six patients and 18 healthy controls was carried out by ELISA, which also showed that alpha-defensin levels were significantly increased in patient lysates when compared with matched controls (p = 0.0197). Plasma from 21 monozygotic twins discordant for schizophrenia and eight healthy unaffected twin pairs was also analyzed for the expression of alpha-defensins by ELISA. Notably both affected and unaffected twins were found to have significantly elevated alpha-defensin levels compared with healthy control twin pairs (p = 0.0014 and p = 0.0115, respectively). Increased expression of alpha-defensins in unaffected as well as affected discordant monozygotic twins is of particular interest as monozygotic twins share genes and usually environmental upbringing. The unaffected twin therefore represents the biological and environmental risk of developing schizophrenia in the absence of overt symptomatology and therapeutic medication. These findings suggest that alpha-defensins could be an important early indicator of the risk of schizophrenia.

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.

Interleukin-1 beta gene polymorphism and its interactions with neuregulin-1 gene polymorphism are associated with schizophrenia

Interleukin-1beta (IL-1beta) and neuregulin-1 (NRG-1) have an important role in development of the central nervous system. Several recent studies suggest that their genetic polymorphisms are associated with schizophrenia. We studied the effects of the IL-1beta gene (IL-1B) -511 and NRG-1 SNP8NRG221533 polymorphisms and their interactions on the risk and age of onset of schizophrenia in 113 Finnish schizophrenic patients and 393 healthy controls. The allele and genotype frequencies of IL-1B and NRG-1 did not differ between schizophrenic patients and healthy controls, but the risk of schizophrenia was more than 10 times higher (odds ratio 10.20, 95% CI 2.53-41.09, p = 0.001) among subjects with the IL-1B 2.2, NRG-1 CC genotypes compared to subjects with the IL-1B 2.2, NRG-1 T-allele carriage. There was also a trend for an association between the interaction between IL-1B and NRG-1 polymorphisms and the age at onset of schizophrenia (chi(2) = 2.80; df = 1; p = 0.09, log rank test). IL-1B-511 allele 1 homozygotes had a significantly higher age of onset than allele 2 carriers (mean age of onset 25.9 +/- 7.7 and 22.7 +/- 5.4 years, t-test: t = 2.46; p = 0.032). Our results suggest that there is an interaction between the IL-1B and NRG-1 genes in schizophrenia. In addition, the IL-1B-511 polymorphism seems to be associated with the age at onset of schizophrenia.

Gene-based SNP mapping of a psychotic bipolar affective disorder linkage region on 22q12.3: association with HMG2L1 and TOM1

Genetic linkage studies in both bipolar affective disorder (BPAD) and schizophrenia have implicated overlapping regions of chromosome 22q. We previously reported that BPAD pedigrees containing multiple members with psychotic symptoms showed suggestive linkage to chromosome 22q12.3. Now we have tested 189 single nucleotide polymorphisms (SNPs) spanning a 3 Mb region around the linkage peak for association with BPAD in 305 families, unrelated cases, and controls. SNPs were selected in or near genes, resulting in coverage at a density of 1 SNP per 6.7 kb across the 22 annotated genes in the region. The strongest signal emerged from family-based association analysis of an 11-SNP, 54 kb haplotype straddling the gene HMG2L1 and part of TOM1. A 3-marker haplotype of SNPs within TOM1 was associated with BPAD (allele-wise P = 0.0011) and with psychotic BPAD (allele-wise P = 0.00049). As hypothesized, the mean odds ratio for the risk alleles across the region was 1.39 in the psychotic but only 0.96 in the non-psychotic subset. Genotype-wise analyses yielded similar results, but the psychotic/non-psychotic distinction was more pronounced with mean odds ratios of 1.91 versus 0.8. Permutation of genotype-wise results for rs2413338 in HMG2L1 showed an empirical P = 0.037 for the difference between subsets. HMG2L1 is a negative regulator of Wnt signaling, a pathway of interest in psychotic BPAD as it is activated by both mood stabilizer and anti-psychotic medications. Further work is needed to confirm these results and uncover the functional variation underlying the association signal.