IL-28B genetic variant is associated with the risk of schizophrenia in the Chinese Han population

A study of the association between polymorphisms in the genes for interleukins IL-6 and IL-10 and negative symptoms subdomains in schizophrenia

BACKGROUND

Schizophrenia is a severe mental illness manifested by various symptoms. Negative symptoms (NS) are associated with disability and poor function of patients. The study of NS neurobiology is complicated by their heterogeneity. Factor analysis revealed two distinct NS subdomains with different pathophysiological mechanisms: volitional pathology, including avolition and apathy (AA), and diminished expression (DE). Inflammation is one mechanism that may underlie NS, including their heterogeneity.

AIMS

To search for the association between genes for interleukins (IL-6 -174 G/C, IL-10 -592 C/A, and IL-10 -1082 G/A) and NS subdomains.

MATERIALS AND METHODS

The study included 275 patients with schizophrenia. NS factors were calculated based on the Positive and Negative Syndromes Scale.

RESULTS

There was a significant main effect of IL-10 polymorphisms on the AA, but not the DE subdomain. Mean score on the AA subdomain was higher in the IL-10 -592 AA compared to the CC genotype. Differences between IL-10 -1082 G/A genotypes were dose dependent. The lowest score was observed for the IL-10 -1082 GG genotype. The association between the IL-6 -174 G/C polymorphism and AA scores was close to the level of significance. Patients with the IL-6 -174 GG genotype had higher score compared to the AA genotype.

CONCLUSION

The results provide further neurobiological evidence for the validity of the NS factor categorization. An imbalance between pro-inflammatory and anti-inflammatory cytokines because of genetic variations is associated with the AA NS subdomain that is supposed to be a more severe aspect of psychopathology compared to the DE.

[Molecular-genetic and immunological aspects of the formation of psychopathological symptoms in schizophrenia]

The authors present the data indicating that the formation of psychopathological symptoms of schizophrenia is due to complex and diverse genetic factors associated with various functional and metabolic pathways at different stages of ontogenesis. Despite the fact that at present the genetic basis of positive and negative symptoms as the main pathophysiological manifestations of schizophrenia remains largely unknown, the current level of research allows the identification of some common and unique associations for positive and negative disorders. Based on the analysis of the literature, the specificity of the association of genetic variants with negative symptoms of schizophrenia is shown. It has been also suggested that genes of the immune system may be specifically associated with negative symptoms of schizophrenia. The relevance of studying the relationship of immune system genes, in particular, pro- and anti-inflammatory cytokines, with dimensional characteristics of negative symptoms (abulia-apathy and expressive deficit) is substantiated. Studies of this type have not yet been conducted, despite accumulating data indicating that the heterogeneity of negative symptoms is based on different neurobiological mechanisms. It is concluded that the immunological and molecular genetic study of the subdomains of psychopathological symptoms can be promising as part of the transition to deep phenotyping, which seems to be especially relevant for the study of such an extremely heterogeneous disease from a clinical point of view as schizophrenia. The development of this area is important for solving the problems of precision medicine, which aims to provide the most effective therapy for a particular patient by stratifying the disease into subclasses, taking into account their biological basis.

Genetic Basis of Positive and Negative Symptom Domains in Schizophrenia

Schizophrenia is a highly heritable disorder, the genetic etiology of which has been well established. Yet despite significant advances in genetics research, the pathophysiological mechanisms of this disorder largely remain unknown. This gap has been attributed to the complexity of the polygenic disorder, which has a heterogeneous clinical profile. Examining the genetic basis of schizophrenia subphenotypes, such as those based on particular symptoms, is thus a useful strategy for decoding the underlying mechanisms. This review of literature examines the recent advances (from 2011) in genetic exploration of positive and negative symptoms in schizophrenia. We searched electronic databases PubMed, Web of Science, and Cumulative Index to Nursing and Allied Health Literature using key words schizophrenia, symptoms, positive symptoms, negative symptoms, cognition, genetics, genes, genetic predisposition, and genotype in various combinations. We identified 115 articles, which are included in the review. Evidence from these studies, most of which are genetic association studies, identifies shared and unique gene associations for the symptom domains. Genes associated with neurotransmitter systems and neuronal development/maintenance primarily constitute the shared associations. Needed are studies that examine the genetic basis of specific symptoms within the broader domains in addition to functional mechanisms. Such investigations are critical to developing precision treatment and care for individuals afflicted with schizophrenia.

IL-28B down-regulates regulatory T cells but does not improve the protective immunity following tuberculosis subunit vaccine immunization

Regulatory T cells (Tregs), which could be down-regulated by IL-28B, were reported to suppress T-cell-mediated immunity. The aim of this study was to investigate the role of IL-28B on the immune responses and protective efficacy of a tuberculosis (TB) subunit vaccine. First, a recombinant adenoviral vector expressing mouse IL-28B (rAd-mIL-28B) was constructed; then C57BL/6 mice were immunized with subunit vaccine ESAT6-Ag85B-Mpt64(190-198)-Mtb8.4-HspX (EAMMH) and rAd-mIL-28B together thrice or primed with Mycobacterium bovis bacillus Calmette-Gue'rin (BCG) and boosted by EAMMH and rAd-mIL-28B twice. At last the immune responses were evaluated, and the mice primed with BCG and boosted by subunit vaccines were challenged with virulent Mycobacterium tuberculosis H37Rv to evaluate the protective efficacy. The results showed that rAd-mIL-28B treatment significantly down-regulated the frequency of Tregs at 4 weeks after the last immunization but did not increase the Th1-type immune responses. Moreover, in the regimen of BCG priming and EAMMH boosting, rAd-mIL-28B treatment did not increase the antigen-specific cellular and humoral immune responses, and consequently did not reduce the bacteria load following H37Rv challenge. Instead, it induced more serious pathology reaction. In conclusion, IL-28B down-regulates Tregs following EAMMH vaccination but does not improve the protective immune responses.

Association between the European GWAS-identified susceptibility locus at chromosome 4p16 and the risk of atrial septal defect: a case-control study in Southwest China and a meta-analysis

Atrial septal defect (ASD) is the third most frequent type of congenital heart anomaly, featuring shunting of blood between the two atria. Gene-environment interaction remains to be an acknowledged cause for ASD occurrence. A recent European genome-wide association study (GWAS) of congenital heart disease (CHD) identified 3 susceptibility SNPs at chromosome 4p16 associated with ASD: rs870142, rs16835979 and rs6824295. A Chinese-GWAS of CHD conducted in the corresponding period did not reveal the 3 susceptibility SNPs, but reported 2 different risk SNPs: rs2474937 and rs1531070. Therefore, we aimed to investigate the associations between the 3 European GWAS-identified susceptibility SNPs and ASD risk in the Han population in southwest China. Additionally, to increase the robustness of our current analysis, we conducted a meta-analysis combining published studies and our current case-control study. We performed association, linkage disequilibrium, and haplotype analysis among the 3 SNPs in 190 ASD cases and 225 age-, sex-, and ethnicity-matched healthy controls. Genotype and allele frequencies among the 3 SNPs showed statistically significant differences between the cases and controls. Our study found that individuals carrying the allele T of rs870142, the allele A of rs16835979, and the allele T of rs6824295 had a respective 50.1% (odds ratio (OR) = 1.501, 95% confidence interval (CI) = 1.122-2.009, P_FDR-BH = 0.018), 48.5% (OR = 1.485, 95%CI = 1.109-1.987, P_FDR-BH = 0.012), and 38.6% (OR = 1.386, 95%CI = 1.042-1.844, P_FDR-BH = 0.025) increased risk to develop ASD than wild-type allele carriers in our study cohort. In the haplotype analysis, we identified a disease-risk haplotype (TAT) (OR = 1.540, 95%CI = 1.030-2.380, P_FDR-BH = 0.016). Our meta-analysis also showed that the investigated SNP was associated with ASD risk (combined OR (95%CI) = 1.35 (1.24-1.46), P < 0.00001). Our study provides compelling evidence to motivate better understanding of the etiology of ASD.

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.

Schizophrenia is primed for an increased expression of depression through activation of immuno-inflammatory, oxidative and nitrosative stress, and tryptophan catabolite pathways

Schizophrenia and depression are two common and debilitating psychiatric conditions. Up to 61% of schizophrenic patients have comorbid clinical depression, often undiagnosed. Both share significant overlaps in underlying biological processes, which are relevant to the course and treatment of both conditions. Shared processes include changes in cell-mediated immune and inflammatory pathways, e.g. increased levels of pro-inflammatory cytokines and a Th1 response; activation of oxidative and nitrosative stress (O&NS) pathways, e.g. increased lipid peroxidation, damage to proteins and DNA; decreased antioxidant levels, e.g. lowered coenzyme Q10, vitamin E, glutathione and melatonin levels; autoimmune responses; and activation of the tryptophan catabolite (TRYCAT) pathway through induction of indoleamine-2,3-dioxygenase. Both show cognitive and neurostructural evidence of a neuroprogressive process. Here we review the interlinked nature of these biological processes, suggesting that schizophrenia is immunologically primed for an increased expression of depression. Such a conceptualization explains, and incorporates, many of the current perspectives on the nature of schizophrenia and depression, and has implications for the nature of classification and treatment of both disorders. An early developmental etiology to schizophrenia, driven by maternal infection, with subsequent impact on offspring immuno-inflammatory responses, creates alterations in the immune pathways, which although priming for depression, also differentiates the two disorders.

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

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