Polymorphisms in immune-inflammatory response genes and the risk of deficit schizophrenia

Immunophenotypes in psychosis: is it a premature inflamm-aging disorder?

Immunopsychiatric field has rapidly accumulated evidence demonstrating the involvement of both innate and adaptive immune components in psychotic disorders such as schizophrenia. Nevertheless, researchers are facing dilemmas of discrepant findings of immunophenotypes both outside and inside the brains of psychotic patients, as discovered by recent meta-analyses. These discrepancies make interpretations and interrogations on their roles in psychosis remain vague and even controversial, regarding whether certain immune cells are more activated or less so, and whether they are causal or consequential, or beneficial or harmful for psychosis. Addressing these issues for psychosis is not at all trivial, as immune cells either outside or inside the brain are an enormously heterogeneous and plastic cell population, falling into a vast range of lineages and subgroups, and functioning differently and malleably in context-dependent manners. This review aims to overview the currently known immunophenotypes of patients with psychosis, and provocatively suggest the premature immune "burnout" or inflamm-aging initiated since organ development as a potential primary mechanism behind these immunophenotypes and the pathogenesis of psychotic disorders.

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

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

The association of cytokines genes (IL-6 and IL-10) with the susceptibility to schizophrenia: A systematic review and meta-analysis

Cytokines are among the important effectors and messenger molecules for restoring the homeostasis tissue after an inflammatory response. The association between IL-6 and IL-10 genes polymorphisms with the schizophrenia susceptibility have yielded controversial results. To reconcile the results, a systematic review followed by meta-analysis was performed to assess the association. We carried out literature searches of PubMed, Scopus, EBSCO, and Web of Sciences databases. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to assess the strength of the association. Subgroup analysis, heterogeneity analyses, and publication bias were also calculated in the meta-analysis. A total of 22 case-control studies, consisting of 4,993 schizophrenic patients and 5,195 healthy controls, were included in the meta-analysis. The meta-analysis suggests that the IL-6 rs1800795 polymorphism displays a protective role against schizophrenia, while the IL-10 rs1800896 and rs1800872 polymorphisms confer an increased risk of schizophrenia. Similar results were found in subgroup analysis by ethnicity. We did not find association between IL-10 rs1800871 polymorphism and schizophrenia susceptibility. Finally, this meta-analysis suggested that the dysregulation of cytokines could lead to the pathogenesis of the schizophrenia.

The relationship between human development and prevalence of deficit schizophrenia: Results from a systematic review and meta-analysis

This study examined the relationship between the prevalence of deficit schizophrenia (DS) and a country's Human Development Index (HDI). A systematic review and meta-analysis of the literature published in the last decade were conducted to acquire data on the worldwide prevalence of deficit syndrome in schizophrenia cohorts and examine the correlation between DS prevalence and the HDI of the countries in the review. Twenty-six studies meeting our eligibility criteria provided prevalence data on DS in 14 countries with both low-to-middle and high-incomes, ranging from 14.34%-to 61.57%. The pooled prevalence of DS was 32.19% (95% CI = 26.17 to 38.52). Statistical analysis yielded a correlation coefficient (r) of -0.518 (95% CI = -0.754 to -0.164; p = 0.007), indicating a moderate inverse correlation between DS prevalence and HDI. This relationship remained significant in partial correlation analysis after controlling for potential sources of bias in the DS estimates (r = -0.489, p = 0.013). Our results show that schizophrenia cohorts from low-to-middle-income countries are more prone to primary and enduring negative symptoms, and contribute to the emerging evidence questioning the axiom that schizophrenia in the developing world has a better course than in high-income countries.

Identifying crucial biomarkers in peripheral blood of schizophrenia and screening therapeutic agents by comprehensive bioinformatics analysis

Schizophrenia (SCZ) is a sophisticated neurodevelopmental disorder, but the mechanisms remain ambiguous. Thus, we analyzed the transcriptomic datasets to investigate the molecular mechanisms of SCZ to pinpoint novel biomarkers and suggest treatment agents. Four peripheral blood datasets were retrieved from the Gene Expression Omnibus (GEO) database, altogether 27 robust Differentially Expressed Genes (DEGs) were ascertained by robust rank aggregation (RRA) methodology. Enrichment analysis, which performed by Enrichr platform, demonstrated that DEGs are predominantly engaged in immune and inflammatory. Protein-protein interaction (PPI) network was constructed by STRING then visualized by Cytoscape. Hub genes identified by cytohubba plug-in were CXCL2, TLR9, SLPI, LY96, G0S2, EGR2, SELENBP1, NDUFA4, GNLY, CCL22. CIBERSORT algorithm was applied to evaluate the situation of immune infiltration, which revealed differences in T-cell CD8, T-cell CD4 memory resting and macrophage M0. The NetworkAnalyst platform was adopted to detect transcription factors (TFs), microRNAs (miRNAs), diseases and chemicals that interact with DEGs, while drugs interacted with DEGs were detected by Enrichr. TFs such as FOXC1, GATA2, NFIC, USF2, E2F1, miRNAs like mir-16-5p, mir-1-3p, mir-124-3p, mir-155-5p, mir-27a-3p are essential in the regulation of DEGs. mir-367-SMAD7-EGR1, mir-367-SMAD7-ARNT, mir-21-SMAD7-EGR1 may be promising biomarkers for SCZ. DEGs were intimately associated with Myocardial Ischemia, Inflammation, Reperfusion Injury. Chemicals such as VPA, cyclosporine, Aflatoxin B1, arsenic trioxide, drugs like diphenylpyraline, trimethoprim, 4-Aminobenzohydrazide, lanatoside C, may have significant implications for treatment of SCZ. These results would shed light on the molecular mechanisms of SCZ and suggest promising diagnostic biomarkers in peripheral blood and therapeutic tactics.

Analysis of selected polymorphisms in FOXP3 gene in a cohort of Egyptian patients with schizophrenia

BACKGROUND

Schizophrenia is a chronic mental disorder with different symptoms. The environmental and genetic factors are suggested to be the etiology of schizophrenia. However, the exact cause and pathogenesis of schizophrenia are still unclear. Different studies suggested that the immune system may have a role in schizophrenia. A genetic study found a relation between the disease and the HLA region on the sixth chromosome. Regulatory T cells (Treg) have a role in the regulation of immune response, especially the balance between TH1 and TH2 cells. The FOXP3 protein is a key regulator for Treg cell's functions. FOXP3 is a transcriptional factor, and its gene is present on the short arm of the X chromosome. The selected SNPs present in the promoter region which act as binding sites for transcriptional factors. This study investigated FOXP3 gene polymorphisms (rs3761548, rs3761549, and rs2232365) in Egyptian patients with schizophrenia. There are no previous studies about the association of FOXP3 gene polymorphisms with schizophrenia. The three selected single-nucleotide polymorphisms (SNPs) were investigated using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for 125 schizophrenia patients and 160 healthy controls. The Positive and Negative Syndrome Scale (PANSS) was used to evaluate patients with schizophrenia.

RESULTS

No significant associations were found between schizophrenia patients and healthy controls for the alleles and genotypes of the selected SNPs (P-value > 0.05). However, a significant association with ACC and ATC haplotypes was detected (P-value 0.001). No significant association was detected between the PANSS score and any of the studied SNPs.

CONCLUSION

The ATC haplotype of rs2232365, rs3761549, and rs3761548 could be considered a risk factor for schizophrenia in Egyptian patients.

[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.

The Role of Cytokines in the Pathogenesis of Schizophrenia

Schizophrenia is a chronic mental illness of unknown etiology. A growing and compelling body of evidence implicates immunologic dysfunction as the key element in its pathomechanism. Cytokines, whose altered levels have been increasingly reported in various patient populations, are the major mediators involved in the coordination of the immune system. The available literature reports both elevated levels of proinflammatory as well as reduced levels of anti-inflammatory cytokines, and their effects on clinical status and neuroimaging changes. There is evidence of at least a partial genetic basis for the association between cytokine alterations and schizophrenia. Two other factors implicated in its development include early childhood trauma and disturbances in the gut microbiome. Moreover, its various subtypes, characterized by individual symptom severity and course, such as deficit schizophrenia, seem to differ in terms of changes in peripheral cytokine levels. While the use of a systematic review methodology could be difficult due to the breadth and diversity of the issues covered in this review, the applied narrative approach allows for a more holistic presentation. The aim of this narrative review was to present up-to-date evidence on cytokine dysregulation in schizophrenia, its effect on the psychopathological presentation, and links with antipsychotic medication. We also attempted to summarize its postulated underpinnings, including early childhood trauma and gut microbiome disturbances, and propose trait and state markers of schizophrenia.

Roles of inflammation in intrinsic pathophysiology and antipsychotic drug-induced metabolic disturbances of schizophrenia

Schizophrenia is a debilitating psychiatric illness that remains poorly understood. While the bulk of symptomatology has classically been associated with disrupted brain functioning, accumulating evidence demonstrates that schizophrenia is characterized by systemic inflammation and disturbances in metabolism. Indeed, metabolic disease is a major determinant of the high mortality rate associated with schizophrenia. Antipsychotic drugs (APDs) have revolutionized management of psychosis, making it possible to rapidly control psychotic symptoms. This has ultimately reduced relapse rates of psychotic episodes and improved overall quality of life for people with schizophrenia. However, long-term APD use has also been associated with significant metabolic disturbances including weight gain, dysglycemia, and worsening of the underlying cardiometabolic disease intrinsic to schizophrenia. While the mechanisms for these intrinsic and medication-induced metabolic effects remain unclear, inflammation appears to play a key role. Here, we review the evidence for roles of inflammatory mechanisms in the disease features of schizophrenia and how these mechanisms interact with APD treatment. We also discuss the effects of common inflammatory mediators on metabolic disease. Then, we review the evidence of intrinsic and APD-mediated effects on systemic inflammation in schizophrenia. Finally, we speculate about possible treatment strategies. Developing an improved understanding of inflammatory processes in schizophrenia may therefore introduce new, more effective options for treating not only schizophrenia but also primary metabolic disorders.

[A role of the immune system in the pathogenesis of schizophrenia]

The review addresses immunological aspects of schizophrenia, a multifactor disease caused by genetic factors, innate disorders of the central nervous system (CNS), including the consequences of perinatal hypoxia and infections, and adverse environmental influences. Neuroinflammation as a part of the pathophysiology of schizophrenia is characterized by the higher transcription of CNS inflammatory mediators, excessive activation of microglia, inhibition of glutamatergic receptors that leads to the decrease in the number of cortical synapses and neuronal apoptosis. The authors discuss a role of genetic polymorphisms of cytokine genes, complement system components etc. The literature data on the changes in systemic immune response and imbalance in Th1/Th2 adaptive immune responses are analyzed as well. Some papers showed higher levels of proinflammatory mediators in CSF and blood of patients with schizophrenia that indicated the involvement of blood brain barrier (BBB) dysfunction. The authors present the recent data on BBB dysfunction in schizophrenia and its role in the pathogenesis of the disease, autoimmunity in patients comparing it with immune activation and genetic predisposition. An important and arguable issues about a role of parasite and viral infections in the pathogenesis of schizophrenia, initiation of immune responses and direct impacts on the brain, an influence of antipsychotic treatment on immunity are discussed. In author's opinion, conflicting results of genetic and immunological studies of schizophrenia may be explained by different methodological approaches to selection of patients and healthy controls and the differences in schizophrenia classification.

IL6/IL6R genetic diversity and plasma IL6 levels in bipolar disorder: An Indo-French study

Reports of association of genetic variants of IL6 and its receptor (IL6R) with psychiatric disorders are inconsistent, and there are few population-based studies thus far in bipolar disorder (BD). We genotyped the IL6 rs1800795 and IL6R rs2228145 polymorphisms in two independent sets of patients exposed to different environmental stimuli such as climatic conditions or specific infectious burden - a French sample and a south Indian Tamil sample of BD with quantitation of circulating plasma IL-6 levels in the latter sub-sample. In both populations, allele and genotype frequencies did not differ significantly between cases and controls for either polymorphism. Upon stratifying based on age at onset, we found no associations with the IL6 rs1800795 variant. However, the IL6R rs2228145 C allele and CC genotype were associated with early onset of disease in the French sample when compared to late onset BD. A similar trend was observed in the Indian population where we also found that plasma IL-6 levels were significantly higher in BD and also in patients who were in residual phase or remission both as compared to controls. Our findings are in favour of a possible trans-ethnic implication of the IL6R genetic diversity in BD and reinforce the notion that IL-6 is an important marker of the operating inflammatory processes in the disease.

First-episode schizophrenia is associated with a reduction of HERV-K methylation in peripheral blood

Human endogenous retroviruses (HERV) have been widely associated with schizophrenia etiology. Aberrant epigenetic processes may play a role in the etiology of schizophrenia. In this study, we tested whether schizophrenia patients at different stages of illness might present alterations in the levels of HERV-K methylation. We recruited 49 first-episode schizophrenia (FES) patients with 47 age- and sex-matched healthy controls (HCs), and 100 multi-episode schizophrenia (MES) patients with 50 age- and sex-matched HCs. Based on the Schedule for Deficit Schizophrenia, patients with MES were also divided into two subgroups: deficit (D-SCZ) and non-deficit schizophrenia (ND-SCZ). DNA methylation levels of HERV-K sequences were examined in peripheral blood leukocytes. We found significantly lower levels of HERV-K methylation in FES patients compared to HCs. Patients with MES and matched HCs had similar levels of HERV-K methylation. There was a significant positive correlation between chlorpromazine equivalent dosage and HERV-K methylation levels in MES patients, but not in FES individuals. No significant differences in HERV-K methylation levels between D-SCZ and ND-SCZ as well as HCs were found. Our results indicate lower HERV-K methylation levels at early stages of schizophrenia. This difference might normalize with subsequent exacerbations of schizophrenia, likely due to the effects of antipsychotics.

Deficit schizophrenia is a discrete diagnostic category defined by neuro-immune and neurocognitive features: results of supervised machine learning

Deficit schizophrenia is characterized by neurocognitive impairments and changes in the patterning of IgA/IgM responses to plasma tryptophan catabolites (TRYCATs). In the current study, supervised pattern recognition methods, including logistic regression analysis (LRA), Support Vector Machine (SVM), and Soft Independent Modeling of Class Analogy (SIMCA), were used to examine whether deficit schizophrenia is a discrete diagnostic class with respect to Consortium To Establish a Registry for Alzheimer's disease (CERAD) and Cambridge Neuropsychological Test Automated Battery (CANTAB) tests and IgA/IgM responses to noxious (NOX) and generally more protective (PRO) TRYCATs. We recruited patients with (n = 40) and without (n = 40) deficit schizophrenia and healthy volunteers (n = 40). The combined use of TRYCAT and CERAD features strongly segregates deficit from nondeficit schizophrenia and healthy controls. Three out of the top five most important features in LRA, SVM and SIMCA agreed, namely two different NOX/PRO TRYCAT ratios and false memory recall. SIMCA shows that deficit schizophrenia is significantly separated from nondeficit schizophrenia and controls with as top 6 features IgA responses to picolinic acid, IgM responses to 3-OH-kynurenine and kynurenic acid, and impairments in Word List Memory and Verbal Fluency Tests and Mini-Mental State Examination. Nevertheless, nondeficit schizophrenia was not significantly separated from controls. The results show that schizophrenia is not a unitary disease with mere continuous differences in severity of illness between apparent subtypes. Deficit schizophrenia is a qualitatively distinct class defined by neuroimmune (autoimmune responses to TRYCATs) and neurocognitive (episodic and semantic memory) features coupled or not with clinical (negative) symptoms.

Association Study of Tumor Necrosis Factor Receptor 1 (TNFR1) Gene Polymorphisms with Schizophrenia in the Polish Population

Schizophrenia is a devastating mental disorder with undetermined aetiology. Previous research has suggested that dysregulation of proinflammatory cytokines and their receptors plays a role in developing schizophrenia. We examined the association of the three single nucleotide polymorphisms (SNPs; rs4149576, rs4149577, and rs1860545) in the tumor necrosis factor receptor 1 (TNFR1) gene with the development and psychopathology of paranoid schizophrenia in the Polish Caucasian sample consisting of 388 patients and 657 control subjects. The psychopathology was assessed using a five-factor model of the Positive and Negative Syndrome Scale (PANSS). SNPs were genotyped using the TaqMan 5'-exonuclease allelic discrimination assay. The SNPs tested were not associated with a predisposition to paranoid schizophrenia in either the entire sample or after stratification according to gender. However, rs4149577 and rs1860545 SNPs were associated with the intensity of the PANSS excitement symptoms in men, which may contribute to the risk of violent behavior. Polymorphisms in the TNFR1 gene may have an impact on the symptomatology of schizophrenia in men.

Assessment of Complement Cascade Components in Patients With Bipolar Disorder

Introduction: The immune system is undoubtedly involved in the pathogenesis of various psychiatric disorders, such as schizophrenia, bipolar disorder, or depression. Although its role is not fully understood, it appears that this area of research can help to understand the etiology of mental illness. One of the components of the human immune system is the complement system, which forms a part of the innate immune response. Physiologically, except for its essential protective role, it is a vital element in the regeneration processes, including neurogenesis. To date, few studies have tried to clarify the role of the complement cascade in mental disorders. Materials and Methods: We evaluated concentrations of C3a, C5a, and C5b-9 complement cascade components in the peripheral blood of 30 patients suffering from bipolar disorder (BD) for at least 10 years, in euthymia, who were not treated with lithium salts. In addition, we divided our study sample into BD type I (BD-I, 22 persons), and BD type II (BD-II, 8 patients). The control group consisted of 30 healthy volunteers matched for age, sex, BMI, and smoking habits. Results: Compared to healthy controls, BD patients had elevated concentrations of all the investigated components. Furthermore, in patients with BD-II, we observed higher concentrations of C5b-9 as compared to patients with BD-I. However, there was a significant effect of BD diagnosis only on the levels of C3a and C5a but not on the level of C5b-9 after adjustment for potential confounding factors. Conclusions: Increased concentrations of components C3a and C5a of the complement system in the investigated group as compared to healthy controls suggest involvement of the complement cascade in the pathogenesis of BD, and provides further evidence of immune system dysregulation in BD patients.

Human Endogenous Retroviral Envelope Protein Syncytin-1 and Inflammatory Abnormalities in Neuropsychological Diseases

Human endogenous retroviruses (HERVs) comprise approximately 8% of the human genome. Recent studies have considered HERVs as potential pathogenic factors. The majority of HERV genes are mutated and not capable of encoding functional proteins; regardless, some HERV genes, such as HERV-W envelope (env) glycoprotein, are known to have intact open reading frames. The HERV-W element on 7q21.2, which encodes a protein referred to as Syncytin-1, participates in human placental morphogenesis and can activate a pro-inflammatory and autoimmune cascade. Neuropsychological disorders are typically linked to inflammatory abnormalities. In this study, we review that Syncytin-1 has been increasingly involved in the development of neuropsychological disorders, such as schizophrenia and multiple sclerosis (MS). This study also presents inflammation imbalances in schizophrenia and MS. More importantly, we discuss the potential role and molecular mechanisms by which Syncytin-1 regulates inflammatory abnormalities in neuropsychological diseases. In summary, Syncytin-1 activity may represent a novel molecular pathogenic mechanism in neuropyschological diseases, such as schizophrenia and MS.