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

Adjunctive canakinumab reduces peripheral inflammation markers and improves positive symptoms in people with schizophrenia and inflammation: A randomized control trial

BACKGROUND

Clinical trials of anti-inflammatories in schizophrenia do not show clear and replicable benefits, possibly because patients were not recruited based on elevated inflammation status. Interleukin 1-beta (IL-1β) mRNA and protein levels are increased in serum, plasma, cerebrospinal fluid, and brain of some chronically ill patients with schizophrenia, first episode psychosis, and clinical high-risk individuals. Canakinumab, an approved anti-IL-1β monoclonal antibody, interferes with the bioactivity of IL-1β and interrupts downstream signaling. However, the extent to which canakinumab reduces peripheral inflammation markers, such as, high sensitivity C-reactive protein (hsCRP) and symptom severity in schizophrenia patients with inflammation is unknown.

TRIAL DESIGN

We conducted a randomized, placebo-controlled, double-blind, parallel groups, 8-week trial of canakinumab in chronically ill patients with schizophrenia who had elevated peripheral inflammation.

METHODS

Twenty-seven patients with schizophrenia or schizoaffective disorder and elevated peripheral inflammation markers (IL-1β, IL-6, hsCRP and/or neutrophil to lymphocyte ratio: NLR) were randomized to a one-time, subcutaneous injection of canakinumab (150 mg) or placebo (normal saline) as an adjunctive antipsychotic treatment. Peripheral blood hsCRP, NLR, IL-1β, IL-6, IL-8 levels were measured at baseline (pre injection) and at 1-, 4- and 8-weeks post injection. Symptom severity was assessed at baseline and 4- and 8-weeks post injection.

RESULTS

Canakinumab significantly reduced peripheral hsCRP over time, F(3, 75) = 5.16, p = 0.003. Significant hsCRP reductions relative to baseline were detected only in the canakinumab group at weeks 1, 4 and 8 (p's = 0.0003, 0.000002, and 0.004, respectively). There were no significant hsCRP changes in the placebo group. Positive symptom severity scores were significantly reduced at week 8 (p = 0.02) in the canakinumab group and week 4 (p = 0.02) in the placebo group. The change in CRP between week 8 and baseline (b = 1.9, p = 0.0002) and between week 4 and baseline (b = 6.0, p = 0.001) were highly significant predictors of week 8 change in PANSS Positive Symptom severity scores. There were no significant changes in negative symptoms, general psychopathology or cognition in either group. Canakinumab was well tolerated and only 7 % discontinued.

CONCLUSIONS

Canakinumab quickly reduces peripheral hsCRP serum levels in patients with schizophrenia and inflammation; after 8 weeks of canakinumab treatment, the reductions in hsCRP are related to reduced positive symptom severity. Future studies should consider increased doses or longer-term treatment to confirm the potential benefits of adjunctive canakinumab in schizophrenia. Australian and New Zealand Clinical Trials Registry number: ACTRN12615000635561.

The functional polymorphisms linked with interleukin-1β gene expression are associated with bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a severe psychiatric illness attributable to multifactorial risk components (e.g. environmental stimuli, neuroinflammation, etc.), and genetic variations affecting these risk components are considered pivotal predisposing factors. The interleukin-1β (IL-1β) gene and its protein product have been repeatedly highlighted in the pathogenesis of BD. As functional polymorphisms and haplotypes linked with IL-1β mRNA expression have been reported, whether they are correlated with the risk of developing BD remains to be tested.

METHODS

To examine whether variations in the IL-1β gene locus confer genetic risk of BD, we recruited 930 BD patients and 912 healthy controls for the current study. All subjects were Han Chinese, and were age- and gender-matched. We tested seven functional single nucleotide polymorphisms (SNPs) spanning the IL-1β gene and one haplotype composed of three SNPs for their associations with risk of BD.

RESULTS

We found that the functional SNPs in the promoter region of IL-1β gene were significantly associated with risk of BD. The haplotype analyses further supported the involvement of IL-1β promoter SNPs in BD. The BD risk SNPs in our study have been previously reported to predict higher IL-1β levels in the brain and peripheral blood, which is consistent with the clinical observation of elevated IL-1β levels in the lymphocytes or peripheral blood of patients with BD compared with healthy subjects.

CONCLUSION

Our results support the contention that IL-1β is likely a risk gene for BD, and further investigations on this gene may promote our understanding and clinical management of this illness.

Influence of genetic variations in IL1B on brain region volumes in bipolar patients and controls

Involvement of the immune system has been implicated in the etiology and pathophysiology of mood disorders, including bipolar disorder. Neuroimaging studies have reported structural brain pathology in bipolar disorder patients, and both levels of and genetic variants in cytokines have been associated with altered volumes of brain regions. The aim of this study was to investigate associations between single nucleotide polymorphisms in the gene coding for the pro-inflammatory cytokine interleukin-1 beta (IL1B) and whole brain grey matter volume, as well as volumes of several brain regions shown to be of importance in mood disorders. Structural magnetic resonance imaging and vertex-based morphometry were used to obtain volume of different brain regions in subjects with bipolar disorder (n=188) and healthy controls (n=54). Four IL1B polymorphisms were genotyped: rs1143623, rs1143627, and rs16944 in the promoter region together with the synonymous variant rs1143634 in the IL1B gene. The genotype distribution did not differ between bipolar subjects and controls. The T allele at rs16944 and the C allele at rs1143627 were associated with increased volumes of the putamen of the left hemisphere in patients and controls, which lends support to the role of this immune system mediator for brain structure.

Increased circulating regulatory T cells in medicated people with schizophrenia

Immunological abnormalities are increasingly reported in people with schizophrenia, but no clear functional biomarkers associated with genetic correlates of the disease have been found. Regulatory T cells (Tregs) are key immunoregulatory cells involved in the control of inflammatory processes and their functions are directly related to the human leucocyte antigen (HLA) gene, which has been implicated in schizophrenia genetic studies. However, there is a lack of studies reporting Treg status in people with schizophrenia. In the current study, the proportion of circulating Tregs was examined using flow cytometry in 26 medicated participants with schizophrenia and 17 healthy controls. Psychiatric symptoms and cognitive function were evaluated using the Scale for the Assessment of Negative Symptoms, the Brief Psychiatric Rating Scale, and the MATRICS Consensus Cognitive Battery. The proportion of Tregs was found to be significantly greater in the schizophrenia group compared to healthy controls. No differences were observed in total lymphocyte counts or CD3+ and CD4+ T cells, confirming a specific effect for Tregs. Elevated Tregs in schizophrenia correlated with fewer negative symptoms, a core domain of the illness. These results suggest that Tregs may contribute to improved negative symptoms in schizophrenia, possibly by counteracting on-going inflammatory processes.

Genetic variability of interleukin-1 beta as prospective factor from developing post-traumatic stress disorder

Individual susceptibility to post-traumatic stress disorder (PTSD) is conditioned by genetic factors, and association between this disorder and polymorphisms of several genes have been shown. The aim of this study was to explore a potential association between single nucleotide polymorphisms (SNP) of the IL-1β gene (IL1B) and PTSD. In genomic DNA samples of PTSD-affected and healthy subjects, the rs16944, rs1143634, rs2853550, rs1143643, and rs1143633 SNPs of IL1B gene have been genotyped. The results obtained demonstrated that IL1B rs1143633*C and rs16944*A minor allele frequency were significantly lower in patients than in controls. Our results confirm that IL1B rs1143633 and rs16944 SNPs are negatively associated with PTSD which allows us to consider them as protective variants for PTSD. IL1B rs1143633*C and rs16944*A minor allele frequencies and carriage rates are significantly lower in the PTSD patients as compared to the controls. These results may provide a base to conclude that above-mentioned alleles can be protective against PTSD, and IL1B gene can be involved in the pathogenesis of this disorder.

Genetic effect of interleukin-1 beta (C-511T) polymorphism on the structural covariance network and white matter integrity in Alzheimer's disease

Background

Inflammatory processes play a pivotal role in the degenerative process of Alzheimer’s disease. In humans, a biallelic (C/T) polymorphism in the promoter region (position-511) (rs16944) of the interleukin-1 beta gene has been significantly associated with differences in the secretory capacity of interleukin-1 beta. In this study, we investigated whether this functional polymorphism mediates the brain networks in patients with Alzheimer’s disease.

Methods

We enrolled a total of 135 patients with Alzheimer’s disease (65 males, 70 females), and investigated their gray matter structural covariance networks using 3D T1 magnetic resonance imaging and their white matter macro-structural integrities using fractional anisotropy. The patients were classified into two genotype groups: C-carriers (n = 108) and TT-carriers (n = 27), and the structural covariance networks were constructed using seed-based analysis focusing on the default mode network medial temporal or dorsal medial subsystem, salience network and executive control network. Neurobehavioral scores were used as the major outcome factors for clinical correlations.

Results

There were no differences between the two genotype groups in the cognitive test scores, seed, or peak cluster volumes and white matter fractional anisotropy. The covariance strength showing C-carriers > TT-carriers was the entorhinal-cingulum axis. There were two peak clusters (Brodmann 6 and 10) in the salience network and four peak clusters (superior prefrontal, precentral, fusiform, and temporal) in the executive control network that showed C-carriers < TT-carriers in covariance strength. The salience network and executive control network peak clusters in the TT group and the default mode network peak clusters in the C-carriers strongly predicted the cognitive test scores.

Conclusions

Interleukin-1 beta C-511 T polymorphism modulates the structural covariance strength on the anterior brain network and entorhinal-interconnected network which were independent of the white matter tract integrity. Depending on the specific C-511 T genotype, different network clusters could predict the cognitive tests.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0791-z) contains supplementary material, which is available to authorized users.

An Association Between Functional Polymorphisms of the Interleukin 1 Gene Complex and Schizophrenia Using Transmission Disequilibrium Test

IL1 gene complex has been implicated in the etiology of schizophrenia. To assess whether IL1 gene complex is associated with susceptibility to schizophrenia in Polish population we conducted family-based study. Functional polymorphisms from IL1A (rs1800587, rs17561, rs11677416), IL1B (rs1143634, rs1143643, rs16944, rs4848306, rs1143623, rs1143633, rs1143627) and IL1RN (rs419598, rs315952, rs9005, rs4251961) genes were genotyped in 143 trio with schizophrenia. Statistical analysis was performed using transmission disequilibrium test. We have found a trend toward an association of rs1143627, rs16944, rs1143623 in IL1B gene with the risk of schizophrenia. Our results show a protective effect of allele T of rs4251961 in IL1RN against schizophrenia. We also performed haplotype analysis of IL1 gene complex and found a trend toward an association with schizophrenia of GAGG haplotype (rs1143627, rs16944, rs1143623, rs4848306) in IL1B gene, haplotypes: TG (rs315952, rs9005) and TT (rs4251961, rs419598) in IL1RN. Haplotype CT (rs4251961, rs419598) in IL1RN was found to be associated with schizophrenia. After correction for multiple testing associations did not reach significance level. Our results might support theory that polymorphisms of interleukin 1 complex genes (rs1143627, rs16944, rs1143623, rs4848306 in IL1B gene and rs4251961, rs419598, rs315952, rs9005 in IL1RN gene) are involved in the pathogenesis of schizophrenia, however, none of the results reach significance level after correction for multiple testing.

Interaction Effects of Season of Birth and Cytokine Genes on Schizotypal Traits in the General Population

Literature suggests that the effect of winter birth on vulnerability to schizophrenia might be mediated by increased expression of proinflammatory cytokines due to prenatal infection and its inadequate regulation by anti-inflammatory factors. As the response of the immune system depends on genotype, this study assessed the interaction effects of cytokine genes and season of birth (SOB) on schizotypy measured with the Schizotypal Personality Questionnaire (SPQ-74). We searched for associations of IL1B rs16944, IL4 rs2243250, and IL-1RN VNTR polymorphisms, SOB, and their interactions with the SPQ-74 total score in a sample of 278 healthy individuals. A significant effect of the IL4 X SOB interaction was found, p = 0.007 and η² = 0.028. We confirmed this effect using an extended sample of 373 individuals. Homozygotes CC born in winter showed the highest SPQ total score and differed significantly from winter-born T allele carriers, p = 0.049. This difference was demonstrated for cognitive-perceptual and disorganized but not interpersonal dimensions. The findings are consistent with the hypothesis that the cytokine genes by SOB interaction can influence variability of schizotypal traits in the general population. The IL4 T allele appeared to have a protective effect against the development of positive and disorganized schizotypal traits in winter-born individuals.

Contribution of IL-10 and its -592 A/C polymorphism to cognitive functions in first-episode drug-naive schizophrenia

Numerous studies have shown that proinflammatory cytokines produced by immune cells in the brain have deleterious effects on cognitive functions. In contrast, IL-10, an anti-inflammatory cytokine, can be neuroprotective and prevent neuronal dysfunction. However, few studies have linked the role of IL-10 to cognitive deficits in schizophrenia. In this study, serum IL-10 levels and genotypes for the IL10 -592 A/C promoter polymorphism were measured in a cohort of first-episode drug-naïve schizophrenic patients (FEDN-S) (n=256) and healthy control subjects (HC) (n=540). All participants were assessed by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), and psychopathology was assessed by the Positive and Negative Syndrome Scale (PANSS). In a separate transcriptomic data set containing 577 healthy human brain samples, we analyzed IL-10 and IL-10 RA/B-associated genetic networks in order to ascertain potential functions for IL-10 in the brain. We found a significant difference in allelic frequency between FEDN-S and HC subjects. The A allelic variant was associated with reduced serum IL-10 levels and worse attentional performance in FEDN-S but not in HC subjects. Moreover, serum IL-10 levels were correlated with the extent of cognitive impairment, especially attentional performance in the schizophrenic A-allele carriers. In human brain transcriptomic coexpression analysis, we found that genes most significantly co-expressed with IL10 were associated with synaptic vesicle transportation, and both IL10RA and IL10RB were most significantly co-expressed not only with genes that regulate inflammation but also with those that participate in synaptic formation. The IL10-592 A/C genetic variant was more common in schizophrenic patients than HC and was associated with lower IL-10 serum levels and worse attentional performance in these patients. Furthermore, the IL10 gene and its receptors in the healthy human brain appear to regulate inflammation and synaptic functions that are important for cognition, and hence its deficiency in schizophrenia may contribute to cognitive impairment.

Epigenetics in Schizophrenia: A Pilot Study of Global DNA Methylation in Different Brain Regions Associated with Higher Cognitive Functions

Attempts to discover genes that are involved in the pathogenesis of major psychiatric disorders have been frustrating and often fruitless. Concern is building about the need to understand the complex ways in which nature and nurture interact to produce mental illness. We analyze the epigenome in several brain regions from schizophrenic patients with severe cognitive impairment using high-resolution (450K) DNA methylation array. We identified 139 differentially methylated CpG sites included in known and novel candidate genes sequences as well as in and intergenic sequences which functions remain unknown. We found that altered DNA methylation is not restricted to a particular region, but includes others such as CpG shelves and gene bodies, indicating the presence of different DNA methylation signatures depending on the brain area analyzed. Our findings suggest that epimutations are not relatables between different tissues or even between tissues' regions, highlighting the need to adequately study brain samples to obtain reliable data concerning the epigenetics of schizophrenia.

Microglial activation and progressive brain changes in schizophrenia

Schizophrenia is a debilitating disorder that typically begins in adolescence and is characterized by perceptual abnormalities, delusions, cognitive and behavioural disturbances and functional impairments. While current treatments can be effective, they are often insufficient to alleviate the full range of symptoms. Schizophrenia is associated with structural brain abnormalities including grey and white matter volume loss and impaired connectivity. Recent findings suggest these abnormalities follow a neuroprogressive course in the earliest stages of the illness, which may be associated with episodes of acute relapse. Neuroinflammation has been proposed as a potential mechanism underlying these brain changes, with evidence of increased density and activation of microglia, immune cells resident in the brain, at various stages of the illness. We review evidence for microglial dysfunction in schizophrenia from both neuroimaging and neuropathological data, with a specific focus on studies examining microglial activation in relation to the pathology of grey and white matter. The studies available indicate that the link between microglial dysfunction and brain change in schizophrenia remains an intriguing hypothesis worthy of further examination. Future studies in schizophrenia should: (i) use multimodal imaging to clarify this association by mapping brain changes longitudinally across illness stages in relation to microglial activation; (ii) clarify the nature of microglial dysfunction with markers specific to activation states and phenotypes; (iii) examine the role of microglia and neurons with reference to their overlapping roles in neuroinflammatory pathways; and (iv) examine the impact of novel immunomodulatory treatments on brain structure in schizophrenia.

Birth Weight and Adult IQ, but Not Anxious-Depressive Psychopathology, Are Associated with Cortical Surface Area: A Study in Twins

Background

Previous research suggests that low birth weight (BW) induces reduced brain cortical surface area (SA) which would persist until at least early adulthood. Moreover, low BW has been linked to psychiatric disorders such as depression and psychological distress, and to altered neurocognitive profiles.

Aims

We present novel findings obtained by analysing high-resolution structural MRI scans of 48 twins; specifically, we aimed: i) to test the BW-SA association in a middle-aged adult sample; and ii) to assess whether either depression/anxiety disorders or intellectual quotient (IQ) influence the BW-SA link, using a monozygotic (MZ) twin design to separate environmental and genetic effects.

Results

Both lower BW and decreased IQ were associated with smaller total and regional cortical SA in adulthood. Within a twin pair, lower BW was related to smaller total cortical and regional SA. In contrast, MZ twin differences in SA were not related to differences in either IQ or depression/anxiety disorders.

Conclusion

The present study supports findings indicating that i) BW has a long-lasting effect on cortical SA, where some familial and environmental influences alter both foetal growth and brain morphology; ii) uniquely environmental factors affecting BW also alter SA; iii) higher IQ correlates with larger SA; and iv) these effects are not modified by internalizing psychopathology.

ZNF804A Transcriptional Networks in Differentiating Neurons Derived from Induced Pluripotent Stem Cells of Human Origin

ZNF804A (Zinc Finger Protein 804A) has been identified as a candidate gene for schizophrenia (SZ), autism spectrum disorders (ASD), and bipolar disorder (BD) in replicated genome wide association studies (GWAS) and by copy number variation (CNV) analysis. Although its function has not been well-characterized, ZNF804A contains a C2H2-type zinc-finger domain, suggesting that it has DNA binding properties, and consequently, a role in regulating gene expression. To further explore the role of ZNF804A on gene expression and its downstream targets, we used a gene knockdown (KD) approach to reduce its expression in neural progenitor cells (NPCs) derived from induced pluripotent stem cells (iPSCs). KD was accomplished by RNA interference (RNAi) using lentiviral particles containing shRNAs that target ZNF804A mRNA. Stable transduced NPC lines were generated after puromycin selection. A control cell line expressing a random (scrambled) shRNA was also generated. Neuronal differentiation was induced, RNA was harvested after 14 days and transcriptome analysis was carried out using RNA-seq. 1815 genes were found to be differentially expressed at a nominally significant level (p<0.05); 809 decreased in expression in the KD samples, while 1106 increased. Of these, 370 achieved genome wide significance (FDR<0.05); 125 were lower in the KD samples, 245 were higher. Pathway analysis showed that genes involved in interferon-signaling were enriched among those that were down-regulated in the KD samples. Correspondingly, ZNF804A KD was found to affect interferon-alpha 2 (IFNA2)-mediated gene expression. The findings suggest that ZNF804A may affect a differentiating neuron’s response to inflammatory cytokines, which is consistent with models of SZ and ASD that support a role for infectious disease, and/or autoimmunity in a subgroup of patients.

Partial genetic deletion of neuregulin 1 modulates the effects of stress on sensorimotor gating, dendritic morphology, and HPA axis activity in adolescent mice

Stress has been linked to the pathogenesis of schizophrenia. Genetic variation in neuregulin 1 (NRG1) increases the risk of developing schizophrenia and may help predict which high-risk individuals will transition to psychosis. NRG1 also modulates sensorimotor gating, a schizophrenia endophenotype. We used an animal model to demonstrate that partial genetic deletion of Nrg1 interacts with stress to promote neurobehavioral deficits of relevance to schizophrenia. Nrg1 heterozygous (HET) mice displayed greater acute stress-induced anxiety-related behavior than wild-type (WT) mice. Repeated stress in adolescence disrupted the normal development of higher prepulse inhibition of startle selectively in Nrg1 HET mice but not in WT mice. Further, repeated stress increased dendritic spine density in pyramidal neurons of the medial prefrontal cortex (mPFC) selectively in Nrg1 HET mice. Partial genetic deletion of Nrg1 also modulated the adaptive response of the hypothalamic-pituitary-adrenal axis to repeated stress, with Nrg1 HET displaying a reduced repeated stress-induced level of plasma corticosterone than WT mice. Our results demonstrate that Nrg1 confers vulnerability to repeated stress-induced sensorimotor gating deficits, dendritic spine growth in the mPFC, and an abberant endocrine response in adolescence.

Heat shock alters the expression of schizophrenia and autism candidate genes in an induced pluripotent stem cell model of the human telencephalon

Schizophrenia (SZ) and autism spectrum disorders (ASD) are highly heritable neuropsychiatric disorders, although environmental factors, such as maternal immune activation (MIA), play a role as well. Cytokines mediate the effects of MIA on neurogenesis and behavior in animal models. However, MIA stimulators can also induce a febrile reaction, which could have independent effects on neurogenesis through heat shock (HS)-regulated cellular stress pathways. However, this has not been well-studied. To help understand the role of fever in MIA, we used a recently described model of human brain development in which induced pluripotent stem cells (iPSCs) differentiate into 3-dimensional neuronal aggregates that resemble a first trimester telencephalon. RNA-seq was carried out on aggregates that were heat shocked at 39°C for 24 hours, along with their control partners maintained at 37°C. 186 genes showed significant differences in expression following HS (p<0.05), including known HS-inducible genes, as expected, as well as those coding for NGFR and a number of SZ and ASD candidates, including SMARCA2, DPP10, ARNT2, AHI1 and ZNF804A. The degree to which the expression of these genes decrease or increase during HS is similar to that found in copy loss and copy gain copy number variants (CNVs), although the effects of HS are likely to be transient. The dramatic effect on the expression of some SZ and ASD genes places HS, and perhaps other cellular stressors, into a common conceptual framework with disease-causing genetic variants. The findings also suggest that some candidate genes that are assumed to have a relatively limited impact on SZ and ASD pathogenesis based on a small number of positive genetic findings, such as SMARCA2 and ARNT2, may in fact have a much more substantial role in these disorders - as targets of common environmental stressors.

Inflammatory cytokine network in schizophrenia

OBJECTIVES

The purpose of this review is to analyse, sum up and discuss the available literature on the role of inflammation and inflammatory cytokines in the pathogenesis of schizophrenia.

METHODS

An electronic literature search of peer-reviewed English language articles using Pubmed was undertaken. These articles together with those published by us provided the background for the present review.

RESULTS

An overview of the available literature on this issue clearly demonstrated the alterations in mRNA and protein expression levels of several proinflammatory and chemotactic cytokines in patients with schizophrenia. Importantly, some of these changes are genetically determined. It was noteworthy that, depending on the study population, some variations of the data obtained are detected.

CONCLUSIONS

Altered inflammatory cytokine production, both genetically and environmentally determined, is implicated in schizophrenia and contributes to disease-associated low-grade systemic inflammation. Proinflammatory and chemotactic cytokines and their receptors may represent additional therapeutic targets for treatment of schizophrenia.

Interleukin 1 beta gene and risk of schizophrenia: detailed case-control and family-based studies and an updated meta-analysis

OBJECTIVE

Interleukin-1 beta (IL-1β) has been implicated in the pathophysiology of schizophrenia. To assess whether the IL1B gene confers increased susceptibility to schizophrenia, we conducted case-control and family-based studies and an updated meta-analysis.

METHODS

We tested the association between IL1B and schizophrenia in 1229 case-control and 112 trio samples using 12 markers, including common tagging single nucleotide variations (SNVs) and a rare non-synonymous variation detected by resequencing the coding regions. We also performed a meta-analysis of rs16944 using a total of 8724 case-control and 201 trio samples from 16 independent populations.

RESULTS

We found no significant associations between any of the 12 SNVs examined and schizophrenia in either case-control or trio samples. Moreover, our meta-analysis results showed no significant association between the common SNV, rs16944, and schizophrenia.

CONCLUSIONS

The present study does not support a role for IL1B in schizophrenia susceptibility.

The neuroimmunology of schizophrenia

Schizophrenia (SCZ) is a polygenic, multi-factorial disorder and a definitive understanding of its pathophysiology has been lacking since it was first described more than a century ago. The predominant pharmacological approach used to treat SCZ is the use of dopamine receptor antagonists. The fact that many patients remain symptomatic, despite complying with medication regimens, emphasises the need for a more encompassing explanation for both the causes and treatment of SCZ. Recent neuroanatomical, neurobiological, environmental and genetic studies have revived the idea that inflammatory pathways are involved in the pathogenesis of SCZ. These new insights have emerged from multiple lines of evidence, including the levels of inflammatory proteins in the central nervous system of patients with SCZ and animal models. This review focuses on aberrant inflammatory mechanisms present both before and during the onset of the psychotic symptoms that characterise SCZ and discusses recent research into adjunctive immune system modulating therapies for its more effective treatment.

Inflammatory cytokines and neurological and neurocognitive alterations in the course of schizophrenia

A growing body of evidence suggests that immune alterations, especially those related to inflammation, are associated with increased risk of schizophrenia and schizophrenia-related brain alterations. Much of this work has focused on the prenatal period, because infections during pregnancy have been repeatedly (albeit inconsistently) linked to risk of schizophrenia. Given that most infections do not cross the placenta, cytokines associated with inflammation (proinflammatory cytokines) have been targeted as potential mediators of the damaging effects of infection on the fetal brain in prenatal studies. Moreover, additional evidence from both human and animal studies suggests links between increased levels of proinflammatory cytokines, immune-related genes, and schizophrenia as well as brain alterations associated with the disorder. Additional support for the role of altered immune factors in the etiology of schizophrenia comes from neuroimaging studies, which have linked proinflammatory cytokine gene polymorphisms with some of the structural and functional abnormalities repeatedly found in schizophrenia. These findings are reviewed and discussed with a life course perspective, examining the contribution of inflammation from the fetal period to disorder presentation. Unexplored areas and future directions, such as the interplay between inflammation, genes, and individual-level environmental factors (e.g., stress, sleep, and nutrition), are also discussed.

Evidence for a dysregulated immune system in the etiology of psychiatric disorders

There is extensive bi-directional communication between the brain and the immune system in both health and disease. In recent years, the role of an altered immune system in the etiology of major psychiatric disorders has become more apparent. Studies have demonstrated that some patients with major psychiatric disorders exhibit characteristic signs of immune dysregulation and that this may be a common pathophysiological mechanism that underlies the development and progression of these disorders. Furthermore, many psychiatric disorders are also often accompanied by chronic medical conditions related to immune dysfunction such as autoimmune diseases, diabetes and atherosclerosis. One of the major psychiatric disorders that has been associated with an altered immune system is schizophrenia, with approximately one third of patients with this disorder showing immunological abnormalities such as an altered cytokine profile in serum and cerebrospinal fluid. An altered cytokine profile is also found in a proportion of patients with major depressive disorder and is thought to be potentially related to the pathophysiology of this disorder. Emerging evidence suggests that altered immune parameters may also be implicated in the neurobiological etiology of autism spectrum disorders. Further support for a role of immune dysregulation in the pathophysiology of these psychiatric disorders comes from studies showing the immunomodulating effects of antipsychotics and antidepressants, and the mood altering effects of anti-inflammatory therapies. This review will not attempt to discuss all of the psychiatric disorders that have been associated with an augmented immune system, but will instead focus on several key disorders where dysregulation of this system has been implicated in their pathophysiology including depression, schizophrenia and autism spectrum disorder.

Association of the interleukin 1 beta gene and brain spontaneous activity in amnestic mild cognitive impairment

Purpose

The inflammatory response has been associated with the pathogenesis of Alzheimer’s disease (AD). The purpose of this study is to determine whether the rs1143627 polymorphism of the interleukin-1 beta (IL-1β) gene moderates functional magnetic resonance imaging (fMRI)-measured brain regional activity in amnestic mild cognitive impairment (aMCI).

Methods

Eighty older participants (47 with aMCI and 33 healthy controls) were recruited for this study. All of the participants were genotyped for variant rs1143627 in the IL1B gene and were scanned using resting-state fMRI. Brain activity was assessed by amplitude of low-frequency fluctuation (ALFF).

Results

aMCI patients had abnormal ALFF in many brain regions, including decreases in the inferior frontal gyrus, the superior temporal lobe and the middle temporal lobe, and increases in the occipital cortex (calcarine), parietal cortex (Pcu) and cerebellar cortex. The regions associated with an interaction of group X genotypes of rs1143627 C/T were the parietal cortex (left Pcu), frontal cortex (left superior, middle, and medial gyrus, right anterior cingulum), occipital cortex (left middle lobe, left cuneus) and the bilateral posterior lobes of the cerebellum. Regarding the behavioral significance, there were significant correlations between ALFF in different regions of the brain and with the cognitive scores of each genotype group.

Conclusions

The present study provided evidence that aMCI patients had abnormal ALFF in many brain regions. Specifically, the rs1143627 C/T polymorphism of the IL1B gene may modulate regional spontaneous brain activity in aMCI patients.

The role of default network deactivation in cognition and disease

A considerable body of evidence has accumulated over recent years on the functions of the default-mode network (DMN)--a set of brain regions whose activity is high when the mind is not engaged in specific behavioral tasks and low during focused attention on the external environment. In this review, we focus on DMN suppression and its functional role in health and disease, summarizing evidence that spans several disciplines, including cognitive neuroscience, pharmacological neuroimaging, clinical neuroscience, and theoretical neuroscience. Collectively, this research highlights the functional relevance of DMN suppression for goal-directed cognition, possibly by reducing goal-irrelevant functions supported by the DMN (e.g., mind-wandering), and illustrates the functional significance of DMN suppression deficits in severe mental illness.