Cytokine hypothesis of schizophrenia pathogenesis: evidence from human studies and animal models

Neurobiology of COVID-19-Associated Psychosis/Schizophrenia: Implication of Epidermal Growth Factor Receptor Signaling

COVID-19 exhibits not only respiratory symptoms but also neurological/psychiatric symptoms rarely including delirium/psychosis. Pathological studies on COVID-19 provide evidence that the cytokine storm, in particular (epidermal growth factor) EGF receptor (EGFR, ErbB1, Her1) activation, plays a central role in the progression of viral replication and lung fibrosis. Of note, SARS-CoV-2 virus (specifically, S1 spike domain) mimics EGF and directly transactivates EGFR, preceding the inflammatory process. In agreement, the anticancer drugs targeting EGFR such as Nimotuzumab and tyrosine kinase inhibitors are markedly effective on COVID-19. However, these data might raise a provisional caution regarding implication of psychiatric disorder such as schizophrenia. The author's group has been investigating the etiologic and neuropathologic associations of EGFR signaling with schizophrenia. There are significant molecular associations between schizophrenia and EGFR ligand levels in blood as well as in the brain. In addition, perinatal challenges of EGFR ligands and intraventricular administration of EGF to rodents and monkeys both resulted in severe behavioral and/or electroencephalographic endophenotypes relevant to this disorder. These animal models also display postpubertal abnormality in soliloquy-like self-vocalization as well as in intercortical functional connectivity. Here, we discuss neuropsychiatric implication of coronavirus infection and its interaction with the EGFR system, by searching related literatures in PubMed database as of the end of 2023.

IL-33/ST2 axis in diverse diseases: regulatory mechanisms and therapeutic potential

Interleukin-33 (IL-33) is a nuclear factor and member of the IL-1 cytokine family. IL-33 is mainly expressed by epithelial and endothelial cells and exerts its function through interaction with various immune cells, and binding to its receptor can form the IL-33/Suppression of tumorigenicity 2 (ST2) signaling pathway. While most cytokines are actively synthesized within cells, IL-33 is produced passively in response to tissue damage or cell necrosis, indicating its role as a signaling molecule following cellular infection, stress, or trauma. IL-33/ST2 signaling pathway has been proved to play diverse role in the pathological process of central nervous system disorders, cancer, fibrosis, autoimmune diseases, etc. Although research on the IL-33/ST2 signaling pathway has deepened recently, relevant treatment strategies have been proposed, and even targeted drugs are in the preclinical stage; further research on the effect of the IL-33/ST2 signaling pathway in different diseases is still necessary, to provide a clearer understanding of the different roles of IL-33/ST2 in disease progression and to develop new drugs and treatment strategies. Because IL-33/ST2 plays an important role in the occurrence and progression of diseases, the study of therapeutic drugs targeting this pathway is also necessary. This review focused on recent studies on the positive or negative role of IL-33/ST2 in different diseases, as well as the current related drugs targeting IL-33/ST2 in the preclinical and clinical stage. The mechanism of IL-33/ST2 in different diseases and its mediating effect on different immune cells have been summarized, as well as the antibody drugs targeting IL-33 or ST2, natural compounds with a mediating effect, and small molecule substances targeting relative pathway. We aim to provide new ideas and treatment strategies for IL-33/ST2-related drugs to treat different diseases.

Comparative Analysis of Serum BAFF and IL-17 Levels Pre- and Post-Antipsychotic Treatment for Acute Schizophrenia

The interplay between the cytokine network and antipsychotic treatment in schizophrenia remains poorly understood. This study aimed to investigate the impact of psychotropic medications on serum levels of IFN-γ, IL-4, TGF-β1, IL-17, and BAFF, and to explore their relationship with psychopathological features. We recruited 63 patients diagnosed with schizophrenia in the acute phase, all of whom were either drug-naïve or had been drug-free for at least three months. Serum levels of IL-4, IFN-γ, TGF-β1, IL-17, and BAFF were measured at baseline and after six months of antipsychotic treatment. The severity of symptoms was assessed using the Brief Psychiatric Rating Scale (BPRS), the Scale for the Assessment of Positive Symptoms (SAPS), and the Scale for the Assessment of Negative Symptoms (SANS). Fifty-two patients completed the six-month follow-up for immunoassay analysis. Antipsychotic treatment led to a significant decrease in serum levels of IFN-γ, TGF-β1, and IL-17, alongside a significant increase in BAFF levels. Changes in IFN-γ were positively correlated with SANS scores and negatively correlated with Global Assessment of Functioning (GAF) scores. Changes in TGF-β1 were negatively correlated with GAF scores. Changes in BAFF were negatively correlated with SAPS scores. Multivariable regression models were used to explore the association between cytokine level changes (IL-17, BAFF, IFN-γ, and TGF-β1) and independent variables, including demographic (gender, age), behavioral (tobacco use), clinical (schizophrenia type, disease course, date of onset, prior treatment), and biological (C-reactive protein (CRP), erythrocyte sedimentation rate (ESR)) factors, as well as standardized assessment scores. No significant associations were found, except for a significant negative correlation between TGF-β1 changes and GAF scores, as well as a positive correlation with age. Interestingly, advanced statistical analyses revealed that only changes in IL-17 and BAFF levels were significantly associated with antipsychotic treatment. Our findings suggest that antipsychotic drugs exert both pro- and anti-inflammatory effects on the cytokine network. The observed modulation of IL-17 and BAFF highlights their potential as future therapeutic targets in schizophrenia.

Onset age moderates the associations between neutrophil-to-lymphocyte ratio and clinical symptoms in first-episode patients with schizophrenia

Patients with schizophrenia with early onset age have been shown to exhibit more severe negative symptoms. Genetic, biomarker, postmortem brain, and imaging studies indicate the involvement of immune abnormalities in the pathophysiology of schizophrenia. In this study, we examined the moderating role of early onset on the associations between clinical symptoms and neutrophil-to-lymphocyte ratio (NLR) in medication-naïve first-episode schizophrenia (MNFES). A total of 97 MNFES patients were recruited. Neutrophil (NEU), LYM, and NLR values were compared between early-onset (EO) and non-early-onset (non-EO) patients with schizophrenia to explore the potential influence of EO on the correlations between NLR and symptoms. The results showed no differences in NEU and NLR values between the EO and non-EO groups. In the EO group, NEU and NLR values significantly correlated with general psychopathology and total score (all p < 0.05), whereas lymphocyte counts were not correlated with symptoms of schizophrenia. NEU and NLR were not associated with symptoms in the non-EO group. Linear regression analysis in the EO group revealed that NEU or NLR values were a predictive biomarker for the clinical symptoms. Our study indicates that EO patients had greater severe negative symptoms compared with non-EO patients. In addition, onset age mediates the relationships of NEU and NLR values with clinical symptoms, suggesting that an immune disturbance, particularly increased innate immune response in EO patients, may be involved in the psychophysiology of schizophrenia.

Ancestral retrovirus envelope protein ERVWE1 upregulates circ_0001810, a potential biomarker for schizophrenia, and induces neuronal mitochondrial dysfunction via activating AK2

BACKGROUND

Increasingly studies highlight the crucial role of the ancestral retrovirus envelope protein ERVWE1 in the pathogenic mechanisms of schizophrenia, a severe psychiatric disorder affecting approximately 1% of the global population. Recent studies also underscore the significance of circular RNAs (circRNAs), crucial for neurogenesis and synaptogenesis, in maintaining neuronal functions. However, the precise relationship between ERVWE1 and circRNAs in the etiology of schizophrenia remains elusive.

RESULTS

This study observed elevated levels of hsa_circ_0001810 (circ_0001810) in the blood samples of schizophrenia patients, displaying a significant positive correlation with ERVWE1 expression. Interestingly, in vivo studies demonstrated that ERVWE1 upregulated circ_0001810 in neuronal cells. Circ_0001810, acting as a competing endogenous RNA (ceRNA), bound to miR-1197 and facilitated the release of adenylate kinase 2 (AK2). The bioinformatics analysis of the schizophrenia datasets revealed increased levels of AK2 and enrichment of mitochondrial dynamics. Notably, miR-1197 was reduced in schizophrenia patients, while AK2 levels were increased. Additionally, AK2 showed positive correlations with ERVWE1 and circ_0001810. Further studies demonstrated that AK2 led to mitochondrial dysfunction, characterized by loss of intracellular ATP, mitochondrial depolarization, and disruption of mitochondrial dynamics. Our comprehensive investigation suggested that ERVWE1 influenced ATP levels, promoted mitochondrial depolarization, and disrupted mitochondrial dynamics through the circ_0001810/AK2 pathway.

CONCLUSIONS

Circ_0001810 and AK2 were increased in schizophrenia and positively correlated with ERVWE1. Importantly, ERVWE1 triggered mitochondrial dysfunction through circ_0001810/miR-1197/AK2 pathway. Recent focus on the impact of mitochondrial dynamics on schizophrenia development had led to our discovery of a novel mechanism by which ERVWE1 contributed to the etiology of schizophrenia, particularly through mitochondrial dynamics. Moreover, these findings collectively proposed that circ_0001810 might serve as a potential blood-based biomarker for schizophrenia. Consistent with our previous theories, ERVWE1 is increasingly recognized as a promising therapeutic target for schizophrenia.

HERV-W upregulation expression in bipolar disorder and schizophrenia: unraveling potential links to systemic immune/inflammation status

BACKGROUND

Bipolar disorder (BD) and schizophrenia (SZ) are the two main mental disorders with unknown etiology that significantly impact individuals' quality of life. The potential pro-inflammatory role in their pathogenesis is postulated and Human Endogenous Retrovirus W (HERV-W) is an emerging candidate to modulate this pathogenic finding. HERVs, ancient retroviruses in the human genome, may play roles in inflammation and disease pathogenesis. Despite HERVs' involvement in autoimmune diseases, their influence on mental disorders remains underexplored. Therefore, the aim of this study was to assess the level of HERV-W-env expression and the systemic inflammatory profile through the concentration of IL-2, IL-4, IL-6, IL-10, TNF-α and INF-γ cytokines in BD and SZ patients.

RESULTS

All participants showed HERV-W-env expression, but its expression was higher in mental disorder patients (p < 0.01) than in control. When separated, SZ individuals exhibited higher HERV-W expression than the control group (p < 0.01). Higher serum levels of TNF-α and IL-10 were found in BD (p = 0.0001 and p = 0.001, respectively) and SZ (p = 0.01) and p = 0.01, respectively) than in the control group, while SZ showed decreased levels IFN-γ and IL-2 as compared to controls (p = 0.05) and BD patients (p = 0.05), respectively. Higher TNF-α/IL-4 and TNF-α/IL-10 ratios, and lower IFN-γ/IL-10 were observed in BD and SZ patients than controls. Significant negative correlation between HERV-W-env expression and IL-10 (r=-0.47 p < 0.05), as well as positive correlations between HERV-W-env expression and TNF-α/IL-10 or IFN-γ/IL-10 ratios (r = 0.48 p < 0.05 and r = 0.46 p < 0.05, respectively) were found in BD patients.

CONCLUSION

These findings suggest not only a potential link between HERV-W-env expression both in BD and SZ, but also a possible involvement of systemic inflammatory status in BD patients.

Gut-Brain Axis Deregulation and Its Possible Contribution to Neurodegenerative Disorders

The gut-brain axis is an essential communication pathway between the central nervous system (CNS) and the gastrointestinal tract. The human microbiota is composed of a diverse and abundant microbial community that compasses more than 100 trillion microorganisms that participate in relevant physiological functions such as host nutrient metabolism, structural integrity, maintenance of the gut mucosal barrier, and immunomodulation. Recent evidence in animal models has been instrumental in demonstrating the possible role of the microbiota in neurodevelopment, neuroinflammation, and behavior. Furthermore, clinical studies suggested that adverse changes in the microbiota can be considered a susceptibility factor for neurological disorders (NDs), such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). In this review, we will discuss evidence describing the role of gut microbes in health and disease as a relevant risk factor in the pathogenesis of neurodegenerative disorders, including AD, PD, HD, and ALS.

Long non-coding RNAs in schizophrenia: Genetic variations, treatment markers and potential targeted signaling pathways

Schizophrenia (SZ), a complex and debilitating spectrum of psychiatric disorders, is now mainly attributed to multifactorial etiology that includes genetic and environmental factors. Long non-coding RNAs (lncRNAs) are gaining popularity as a way to better understand the comprehensive mechanisms beneath the clinical manifestation of SZ. Only in recent years has it been elucidated that mammalian genomes encode thousands of lncRNAs. Strikingly, roughly 30-40% of these lncRNAs are extensively expressed in different regions across the brain, which may be closely associated with SZ. The therapeutic and adverse effects of atypical antipsychotic drugs (AAPDs) are partially reflected by their role in the regulation of lncRNAs. This begs the question directly, do any lncRNAs exist as biomarkers for AAPDs treatment? Furthermore, we comprehend a range of mechanistic investigations that have revealed the regulatory roles for lncRNAs both involved in the brain and the periphery of SZ. More crucially, we also combine insights from a variety of signaling pathways to argue that lncRNAs probably play critical roles in SZ via their interactive downstream factors. This review provides a thorough understanding regarding dysregulation of lncRNAs, corresponding genetic alternations, as well as their potential regulatory roles in the pathology of SZ, which might help reveal useful therapeutic targets in SZ.

Schizophrenia Animal Modeling with Epidermal Growth Factor and Its Homologs: Their Connections to the Inflammatory Pathway and the Dopamine System

Epidermal growth factor (EGF) and its homologs, such as neuregulins, bind to ErbB (Her) receptor kinases and regulate glial differentiation and dopaminergic/GABAergic maturation in the brain and are therefore implicated in schizophrenia neuropathology involving these cell abnormalities. In this review, we summarize the biological activities of the EGF family and its neuropathologic association with schizophrenia, mainly overviewing our previous model studies and the related articles. Transgenic mice as well as the rat/monkey models established by perinatal challenges of EGF or its homologs consistently exhibit various behavioral endophenotypes relevant to schizophrenia. In particular, post-pubertal elevation in baseline dopaminergic activity may illustrate the abnormal behaviors relevant to positive and negative symptoms as well as to the timing of this behavioral onset. With the given molecular interaction and transactivation of ErbB receptor kinases with Toll-like receptors (TLRs), EGF/ErbB signals are recruited by viral infection and inflammatory diseases such as COVID-19-mediated pneumonia and poxvirus-mediated fibroma and implicated in the immune-inflammatory hypothesis of schizophrenia. Finally, we also discuss the interaction of clozapine with ErbB receptor kinases as well as new antipsychotic development targeting these receptors.

Infections During Pregnancy and Risks for Adult Psychosis: Findings from the New England Family Study

For the past 40 years, our team has conducted a unique program of research investigating the prenatal risks for schizophrenia and related adult psychiatric disorders. The New England Family Study is a long-term prospective cohort study of over 16,000 individuals followed from the prenatal period for over 50 years. This chapter summarizes several major phases and findings from this work, highlighting recent results on maternal prenatal bacterial infections and brain imaging. Implications regarding the causes and potential prevention of major psychotic disorders are discussed.

Exploring the role of ketone bodies in the diagnosis and treatment of psychiatric disorders

In recent times, advances in the field of metabolomics have shed greater light on the role of metabolic disturbances in neuropsychiatric conditions. The following review explores the role of ketone bodies and ketosis in both the diagnosis and treatment of three major psychiatric disorders: major depressive disorder, anxiety disorders, and schizophrenia. Distinction is made between the potential therapeutic effects of the ketogenic diet and exogenous ketone preparations, as exogenous ketones in particular offer a standardized, reproducible manner for inducing ketosis. Compelling associations between symptoms of mental distress and dysregulation in central nervous system ketone metabolism have been demonstrated in preclinical studies with putative neuroprotective effects of ketone bodies being elucidated, including effects on inflammasomes and the promotion of neurogenesis in the central nervous system. Despite emerging pre-clinical data, clinical research on ketone body effectiveness as a treatment option for psychiatric disorders remains lacking. This gap in understanding warrants further investigating, especially considering that safe and acceptable ways of inducing ketosis are readily available.

Endocytosis is required for consolidation of pattern-separated memories in the perirhinal cortex

Introduction

The ability to separate similar experiences into differentiated representations is proposed to be based on a computational process called pattern separation, and it is one of the key characteristics of episodic memory. Although pattern separation has been mainly studied in the dentate gyrus of the hippocampus, this cognitive function if thought to take place also in other regions of the brain. The perirhinal cortex is important for the acquisition and storage of object memories, and in particular for object memory differentiation. The present study was devoted to investigating the importance of the cellular mechanism of endocytosis for object memory differentiation in the perirhinal cortex and its association with brain-derived neurotrophic factor, which was previously shown to be critical for the pattern separation mechanism in this structure.

Methods

We used a modified version of the object recognition memory task and intracerebral delivery of a peptide (Tat-P4) into the perirhinal cortex to block endocytosis.

Results

We found that endocytosis is necessary for pattern separation in the perirhinal cortex. We also provide evidence from a molecular disconnection experiment that BDNF and endocytosis-related mechanisms interact for memory discrimination in both male and female rats.

Discussion

Our experiments suggest that BDNF and endocytosis are essential for consolidation of separate object memories and a part of a time-restricted, protein synthesis-dependent mechanism of memory stabilization in Prh during storage of object representations.

Catalase and interleukin-6 serum elevation in a prediction of treatment-resistance in male schizophrenia patients

BACKGROUND

Oxidative stress (OS) and neuroinflammatory pathways play an important role in the pathophysiology of schizophrenia. The present study investigated the relationship between OS, inflammatory cytokines, and clinical features in male patients with treatment-resistant schizophrenia (TRS).

METHOD

We measured plasma OS parameters, including manganese-superoxide dismutase (Mn-SOD), copper/zinc-containing SOD (CuZn-SOD), total-SOD (T-SOD), malondialdehyde (MDA), catalase (CAT), and glutathione peroxidase (GSH-Px); and serum inflammatory cytokines, including interleukin (IL)- 1α, IL-6, tumor necrosis factor-alpha (TNF-α), and interferon (IFN)-γ, from 80 male patients with chronic schizophrenia (31 had TRS and 49 had chronic stable schizophrenia (CSS)), and 42 healthy controls. The severity of psychotic symptoms was evaluated using the Positive and Negative Syndrome Scale (PANSS).

RESULTS

Compared with healthy controls, plasma Mn-SOD, CuZn-SOD, T-SOD, GSH-Px, and MDA levels were significantly lower, while CAT and serum IL-6 levels were higher in both TRS and CSS male patients (all P < 0.05). Significant differences in the activities of CAT (F = 6.068, P = 0.016) and IL-6 levels (F = 6.876, P = 0.011) were observed between TRS and CSS male patients after analysis of covariance. Moreover, a significant positive correlation was found between IL-6 levels and PANSS general psychopathology subscores (r = 0.485, P = 0.006) and between CAT activity and PANSS total scores (r = 0.409, P = 0.022) in TRS male patients. CAT and IL-6 levels were predictors for TRS. Additionally, in chronic schizophrenia patients, a significant positive correlation was observed between IL-6 and GSH-Px (r = 0.292, P = 0.012), and the interaction effect of IL-6 and GSH-Px was positively associated with PANSS general psychopathology scores (r = 0.287, P = 0.014).

CONCLUSION

This preliminary study indicated that variations in OS and inflammatory cytokines may be involved in psychopathology for patients with chronic schizophrenia, especially in male patients with TRS.

Peripheral inflammation levels associated with degree of advanced brain aging in schizophrenia

Brain structural abnormalities have been demonstrated in schizophrenia (SZ); these resemble those seen in typical aging, but are seen at younger ages. Furthermore, SZ is associated with accelerated global brain aging, as measured by brain structure-based brain predicted age difference (Brain-PAD). High heterogeneity exists in the degree of brain abnormalities in SZ, and individual differences may be related to levels of peripheral inflammation and may relate to cognitive deficits and negative symptoms. The goal of our study was to investigate the relationship between brain aging, peripheral inflammation, and symptoms of SZ. We hypothesized older brain-PAD in SZ vs. healthy comparison (HC) participants, as well as positive relationships of brain-PAD with peripheral inflammation markers and symptoms in SZ. We analyzed data from two cross-sectional studies in SZ (n = 26; M/F: 21/5) and HC (n = 28; 20/8) (22-64 years). Brain-PAD was calculated using a previously validated Gaussian process regression model applied to raw T1-weighted MRI data. Plasma levels of inflammatory biomarkers (CRP, Eotaxin, Fractalkine, IP10, IL6, IL10, ICAM1, IFNγ, MCP1, MIP1β, SAA, TNFα, VEGF, VCAM1) and cognitive and negative symptoms were assessed. We observed a higher brain-PAD in SZ vs. HC, and advanced brain age relative to chronological age was related to higher peripheral levels of TNFα in the overall group and in the SZ group; other inflammatory markers were not related to brain-PAD. Within the SZ group, we observed no association between cognitive or negative symptoms and brain-PAD. These results support our hypothesis of advanced brain aging in SZ. Furthermore, our findings on the relationship of the pro-inflammatory cytokine TNFα with higher brain-PAD of SZ are relevant to explain heterogeneity of brain ages in SZ, but we did not find strong evidence for cognitive or negative symptom relationships with brain-PAD.

Increased self-triggered vocalizations in an epidermal growth factor-induced rat model for schizophrenia

Rats elicit two types of ultrasonic vocalizations (USVs), positive (30–80 kHz; high pitch) and negative (10–30 kHz; low pitch) voices. As patients with schizophrenia often exhibit soliloquy-like symptoms, we explored whether an animal model for schizophrenia is similarly characterized by such self-triggered vocalizations. We prepared the animal model by administering an inflammatory cytokine, epidermal growth factor (EGF), to rat neonates, which later develop behavioral and electroencephalographic deficits relevant to schizophrenia. EGF model rats and controls at young (8–10 weeks old) and mature (12–14 weeks old) adult stages were subjected to acclimation, female pairing, and vocalization sessions. In acclimation sessions, low pitch USVs at the mature adult stage were more frequent in EGF model rats than in controls. In the vocalization session, the occurrences of low pitch self-triggered USVs were higher in EGF model rats in both age groups, although this group difference was eliminated by their risperidone treatment. Unlike conventional negative USVs of rats, however, the present low pitch self-triggered USVs had short durations of 10–30 ms. These results suggest the potential that self-triggered vocalization might serve as a translatable pathological trait of schizophrenia to animal models.

Imprecise Predictive Coding Is at the Core of Classical Schizophrenia

Current diagnostic criteria for schizophrenia place emphasis on delusions and hallucinations, whereas the classical descriptions of schizophrenia by Kraepelin and Bleuler emphasized disorganization and impoverishment of mental activity. Despite the availability of antipsychotic medication for treating delusions and hallucinations, many patients continue to experience persisting disability. Improving treatment requires a better understanding of the processes leading to persisting disability. We recently introduced the term classical schizophrenia to describe cases with disorganized and impoverished mental activity, cognitive impairment and predisposition to persisting disability. Recent evidence reveals that a polygenic score indicating risk for schizophrenia predicts severity of the features of classical schizophrenia: disorganization, and to a lesser extent, impoverishment of mental activity and cognitive impairment. Current understanding of brain function attributes a cardinal role to predictive coding: the process of generating models of the world that are successively updated in light of confirmation or contradiction by subsequent sensory information. It has been proposed that abnormalities of these predictive processes account for delusions and hallucinations. Here we examine the evidence provided by electrophysiology and fMRI indicating that imprecise predictive coding is the core pathological process in classical schizophrenia, accounting for disorganization, psychomotor poverty and cognitive impairment. Functional imaging reveals aberrant brain activity at network hubs engaged during encoding of predictions. We discuss the possibility that frequent prediction errors might promote excess release of the neurotransmitter, dopamine, thereby accounting for the occurrence of episodes of florid psychotic symptoms including delusions and hallucinations in classical schizophrenia. While the predictive coding hypotheses partially accounts for the time-course of classical schizophrenia, the overall body of evidence indicates that environmental factors also contribute. We discuss the evidence that chronic inflammation is a mechanism that might link diverse genetic and environmental etiological factors, and contribute to the proposed imprecision of predictive coding.

Disorganization of Oscillatory Activity in Animal Models of Schizophrenia

Schizophrenia is a chronic, debilitating disorder with diverse symptomatology, including disorganized cognition and behavior. Despite considerable research effort, we have only a limited understanding of the underlying brain dysfunction. In this article, we review the potential role of oscillatory circuits in the disorder with a particular focus on the hippocampus, a region that encodes sequential information across time and space, as well as the frontal cortex. Several mechanistic explanations of schizophrenia propose that a loss of oscillatory synchrony between and within these brain regions may underlie some of the symptoms of the disorder. We describe how these oscillations are affected in several animal models of schizophrenia, including models of genetic risk, maternal immune activation (MIA) models, and models of NMDA receptor hypofunction. We then critically discuss the evidence for disorganized oscillatory activity in these models, with a focus on gamma, sharp wave ripple, and theta activity, including the role of cross-frequency coupling as a synchronizing mechanism. Finally, we focus on phase precession, which is an oscillatory phenomenon whereby individual hippocampal place cells systematically advance their firing phase against the background theta oscillation. Phase precession is important because it allows sequential experience to be compressed into a single 120 ms theta cycle (known as a 'theta sequence'). This time window is appropriate for the induction of synaptic plasticity. We describe how disruption of phase precession could disorganize sequential processing, and thereby disrupt the ordered storage of information. A similar dysfunction in schizophrenia may contribute to cognitive symptoms, including deficits in episodic memory, working memory, and future planning.

Organoid modeling of Zika and herpes simplex virus 1 infections reveals virus-specific responses leading to microcephaly

Viral infection in early pregnancy is a major cause of microcephaly. However, how distinct viruses impair human brain development remains poorly understood. Here we use human brain organoids to study the mechanisms underlying microcephaly caused by Zika virus (ZIKV) and herpes simplex virus (HSV-1). We find that both viruses efficiently replicate in brain organoids and attenuate their growth by causing cell death. However, transcriptional profiling reveals that ZIKV and HSV-1 elicit distinct cellular responses and that HSV-1 uniquely impairs neuroepithelial identity. Furthermore, we demonstrate that, although both viruses fail to potently induce the type I interferon system, the organoid defects caused by their infection can be rescued by distinct type I interferons. These phenotypes are not seen in 2D cultures, highlighting the superiority of brain organoids in modeling viral infections. These results uncover virus-specific mechanisms and complex cellular immune defenses associated with virus-induced microcephaly.

Elevated levels of IL-18 associated with schizophrenia and first episode psychosis: A systematic review and meta-analysis

AIM

To determine whether interleukin 18 (IL-18) is elevated in the blood of schizophrenia (SCZ) and first episode psychosis patients, as well as investigate whether this potential relationship is causal.

METHOD

We conducted a systematic review and meta-analysis of IL-18 levels in the blood of SCZ patients, comprising of both chronic and first episode psychosis (FEP) cohorts. To investigate causality, we undertook the two-sample Mendelian randomization (MR) study.

RESULTS

A total of eight studies were included in our meta-analysis, our results did indeed show an association between elevated levels of IL-18 and SCZ compared to healthy controls (Z = 3.50, P = .0005). This association remained significant in subsequent subgroup analyses for chronic (Z = 3.15, P = .002) and achieved borderline significance in FEP (Z = 1.93, P = .05) SCZ. Our MR analysis failed to detect any causal relationship between IL-18 levels and SCZ.

CONCLUSION

The results of our study demonstrate that even though IL-18 levels are elevated in SCZ patients, IL-18 levels do not seem to cause of the disorder itself. Our findings suggest that IL-18 may have utility as a biomarker of SCZ and aid in research into the early intervention of the disease.

Accelerated aging signatures in subjects with schizophrenia and their unaffected siblings

Schizophrenia (SZ) is a chronic debilitating disease. Subjects with SZ have significant shorter life expectancy. Growing evidence suggests that a process of pathological accelerated aging occurs in SZ, leading to early development of severe clinical diseases and worse morbimortality. Furthermore, unaffected relatives can share certain endophenotypes with subjects with SZ. We aim to characterize accelerated aging as a possible endophenotype of schizophrenia by using a machine learning (ML) model of peripheral biomarkers to accurately differentiate subjects with SZ (n = 35), their unaffected siblings (SB, n = 36) and healthy controls (HC, n = 47). We used a random forest algorithm that included biomarkers related to aging: eotaxins CCL-11 and CCL-24; the oxidative stress markers thiobarbituric acid-reactive substances (TBARS), protein carbonyl content (PCC), glutathione peroxidase (GPx); and telomere length (TL). The ML algorithm of biomarkers was able to distinguish individuals with SZ from HC with prediction accuracy of 79.7%, SZ from SB with 62.5% accuracy and SB from HC with 75.5% accuracy. These results support the hypothesis that a pathological accelerated aging might occur in SZ, and this pathological aging could be an endophenotype of the disease, once this profile was also observed in SB, suggesting that SB might suffer from an accelerated aging in some level.

Association of Polymorphism −174G/C Interleukin-6 (IL-6) and Schizophrenia in Bataknese Population

BACKGROUND: Schizophrenia is a mental disorder characterized by positive symptoms, negative, and cognitive deficits. Polymorphism of −174G/C interleukin-6 position of the promoter has been described as one of polymorphism that believes have association with schizophrenia and Batak people have a philosophy of life, principles, and at the same time as a structure and system in society called Dalihan na Tolu. This Dalihan na Tolu has a role in the Batak customary marriage laws that cannot be separated during a customary marriage ceremony according to the traditions of the Batak people. This system causes most Batak people to marry each other so that the purity of the population is maintained and can be applied according to Hardy-Weinberg Equilibrium. AIM: Hence, we looked for association in the polymorphism of −174G/C interleukin-6 between people with schizophrenia of the Bataknese population and healthy controls. METHODS: We conducted a cross-sectional study that included 75 people with schizophrenia in the Bataknese population and 75 healthy controls with the same ethnic group. The alleles and genotypes polymorphisms were compared between people with schizophrenia in the Bataknese population and healthy controls and were tested statistically using Chi-square. RESULTS: Frequency of appearance of allele and genotype of −174G/C polymorphism found that there were significant differences in both alleles and genotypes between groups of people with schizophrenia and healthy control groups (p < 0.001) and −174G/C polymorphisms were risk factors for schizophrenia statistically in the Bataknese population (Odds Ratio >1). CONCLUSIONS: We report an association of −174G/C polymorphism and schizophrenia in Bataknese population and polymorphism of −174G/C may be one of the risk factors for schizophrenia in the Bataknese population.

High mobility group box-1 levels in schizophrenia: Potential biomarker of remission phase

Background: Schizophrenia is a chronic mental disorder, characterized byacute exacerbation and remission phases. Immune system has a role in the pathophysiology of schizophrenia. High mobility group box-1 (HMGB-1) is a macrophage secreted protein activating immune cells to produce cytokines. The aim of this study was to evaluate HMGB-1 levels among patients with schizophrenia both in acute exacerbation and remission phases. Methods: Consecutive schizophrenia patients in acute exacerbation and remission phases were enrolled and compared with each other and with age-sex matched healthy subjects. Patients were assessed with the Scale for the Assessment of Positive Symptoms (SAPS), Scale for the Assessment of Negative Symptoms (SANS), Brief Psychiatric Rating Scale (BPRS), Clinical Global Impression Scale (CGI). Results: Mean HMGB-1 levels were not significantly different in acute exacerbation phase versus remission phase schizophrenia patients (2.139±0.564 g/L vs. 2.326± 0.471 g/L, p=0.335) and both were individually higher than the control group (1.791±0.444 g/L, p=0.05 for acute exacerbation vs control, p=0.002 for remission vs control). In remission phase schizophrenic patients, HMGB-1 levels were positively correlated with Scale For The Assessment of Positive Symptoms (r=0.447, p=0.015) and BPRS (r=0.397, p=0.033) scores and HMGB-1 levels were independently associated with BPRS. Conclusions: Serum HMGB-1 levels were shown to be increased in patients with schizophrenia patients irrespective of phase, there were no differences between patients in acute exacerbation and remission phase in terms of biomarker and HMGB-1 levels were related to symptom severity according to psychiatric scales among patients in remission phase of schizophrenia.

Inter-breeder differences in prepulse inhibition deficits of C57BL/6J mice in a maternal immune activation model

Genetic and environmental factors interact with each other to influence the risk of various psychiatric diseases; however, the intensity and nature of their interactions remain to be elucidated. We established a maternal infection model using polyinosinic-polycytidylic acid (Poly(I:C)) to determine the relationship between the maternal breeding environment and behavioral changes in the offspring. We purchased pregnant C57BL/6J mice from three breeders and administered Poly(I:C) (2 mg/kg) intravenously in their tail vein on gestation day 15. The offspring were raised to 8-12 weeks old and subjected to the acoustic startle tests to compare their startle response intensity, prepulse inhibition levels, and degree of the adaptation of the startle response. No statistical interaction between Poly(I:C) administration and sex was observed for prepulse inhibition; thus, male and female mice were analyzed together. There was a statistical interaction between the breeder origin of offspring and prepulse inhibition; the Poly(I:C) challenge significantly decreased prepulse inhibition levels of the offspring born to the pregnant dams from Breeder A but not those from the other breeders. However, we failed to detect significant inter-breeder differences in Poly(I:C) effects on startle response and on startle adaptation with the given number of mice examined. The rearing environment of mouse dams has a prominent effect on the Poly(I:C)-induced prepulse inhibition deficits in this maternal immune activation model.

Interplay of Good Bacteria and Central Nervous System: Cognitive Aspects and Mechanistic Considerations

The human gastrointestinal tract hosts trillions of microorganisms that is called “gut microbiota.” The gut microbiota is involved in a wide variety of physiological features and functions of the body. Thus, it is not surprising that any damage to the gut microbiota is associated with disorders in different body systems. Probiotics, defined as living microorganisms with health benefits for the host, can support or restore the composition of the gut microbiota. Numerous investigations have proved a relationship between the gut microbiota with normal brain function as well as many brain diseases, in which cognitive dysfunction is a common clinical problem. On the other hand, increasing evidence suggests that the existence of a healthy gut microbiota is crucial for normal cognitive processing. In this regard, interplay of the gut microbiota and cognition has been under focus of recent researches. In the present paper, I review findings of the studies considering beneficial effects of either gut microbiota or probiotic bacteria on the brain cognitive function in the healthy and disease statuses.

Detailed Postmortem Profiling of Inflammatory Mediators Expression Revealed Post-inflammatory Alternation in the Superior Temporal Gyrus of Schizophrenia

Recent studies have lent support to the possibility that inflammation is associated with the pathology of schizophrenia. In the study of measurement of inflammatory mediators, which are markers of inflammation, elevated inflammatory cytokine levels in the brain and blood have been reported in patients with schizophrenia. Several postmortem brain studies have also reported changes in the expression of inflammatory cytokines. However, it is not clear how these elevated inflammatory cytokines interact with other inflammatory mediators, and their association with the pathology of schizophrenia. We comprehensively investigated the expression of 30 inflammatory mediators in the superior temporal gyrus (STG) of 24 patients with schizophrenia and 26 controls using a multiplex method. Overall, inflammatory mediator expression in the STG was mostly unchanged. However, the expression of interleukin (IL)1-α and interferon-gamma-inducible protein (IP)-10 was decreased [IL-1α, median (IQR), 0.51 (0.37-0.70) vs. 0.87 (0.47-1.23), p = 0.01; IP-10, 13.99 (8.00-36.64) vs. 30.29 (10.23-134.73), p = 0.05], whereas that of IFN-α was increased [2.34 (1.84-4.48) vs. 1.94 (1.39-2.36), p = 0.04] in schizophrenia, although these alterations did not remain significant after multiple testing. Clustering based on inflammatory mediator expression pattern and analysis of upstream transcription factors using pathway analysis revealed that the suppression of IL-1α and IP-10 protein expression may be induced by regulation of a common upstream pathway. Neuroinflammation is important in understanding the biology of schizophrenia. While neuroimaging has been previously used, direct observation to determine the expression of inflammatory mediators is necessary. In this study, we identified protein changes, previously unreported, using comprehensive protein analysis in STG. These results provide insight into post-inflammatory alternation in chronic schizophrenia.

The Differences between Gluten Sensitivity, Intestinal Biomarkers and Immune Biomarkers in Patients with First-Episode and Chronic Schizophrenia

Schizophrenia is a heterogeneous disorder without a fully elucidated etiology and mechanisms. One likely explanation for the development of schizophrenia is low-grade inflammation, possibly caused by processes in the gastrointestinal tract related to gluten sensitivity. The aims of this study were to: (1) compare levels of markers of gluten sensitivity, inflammation and gut permeability, and (2) determine associations between gluten sensitivity, inflammation, and intestinal permeability in patients with first-episode/chronic (FS/CS) schizophrenia and healthy individuals (HC). The total sample comprised 162 individuals (52 FS; 50 CS, and 60 HC). The examination included clinical variables, nutritional assessment, and serum concentrations of: high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), soluble CD14 (sCD14), anti-Saccharomyces cerevisiae antibody (ASCA), antigliadin antibodies (AGA) IgA/IgG, antibodies against tissue transglutaminase 2 (anti-tTG) IgA, anti-deamidated gliadin peptides (anti-DGP) IgG. A significant difference between groups was found in sCD14, ASCA, hs-CRP, IL-6 and AGA IgA levels. AGA IgG/IgA levels were higher in the FS (11.54%; 30.77%) and CS (26%; 20%) groups compared to HC. The association between intestinal permeability and inflammation in the schizophrenic patients only was noted. The risk for developing schizophrenia was odds ratio (OR) = 4.35 (95% confidence interval (CI 1.23-15.39) for AGA IgA and 3.08 (95% CI 1.19-7.99) for positive AGA IgG. Inflammation and food hypersensitivity reactions initiated by increased intestinal permeability may contribute to the pathophysiology of schizophrenia. The immune response to gluten in FS differs from that found in CS.

Effects of Prenatal Exposure to Inflammation Coupled With Stress Exposure During Adolescence on Cognition and Synaptic Protein Levels in Aged CD-1 Mice

Age-associated impairment of spatial learning and memory (AISLM) presents substantial challenges to our health and society. Increasing evidence has indicated that embryonic exposure to inflammation accelerates the AISLM, and this can be attributable, at least partly, to changed synaptic plasticity associated with the activities of various proteins. However, it is still uncertain whether social psychological factors affect this AISLM and/or the expression of synaptic protein-associated genes. Synaptotagmin-1 (Syt1) and activity-regulated cytoskeleton-associated protein (Arc) are two synaptic proteins closely related to cognitive functions. In this study, pregnant CD-1 mice received daily intraperitoneal injections of lipopolysaccharide (LPS) (50 μg/kg) or normal saline at days 15-17 of gestation, and half of the offspring of each group were then subjected to stress for 28 days in adolescence. The Morris water maze (MWM) test was used to separately evaluate spatial learning and memory at 3 and 15 months of age, while western blotting and RNAscope assays were used to measure the protein and mRNA levels of Arc and Syt1 in the hippocampus. The results showed that, at 15 months of age, control mice had worse cognitive ability and higher protein and mRNA levels of Arc and Syt1 than their younger counterparts. Embryonic exposure to inflammation or exposure to stress in adolescence aggravated the AISLM, as well as the age-related increase in Arc and Syt1 expression. Moreover, the hippocampal protein and mRNA levels of Arc and Syt1 were significantly correlated with the performance in the learning and memory periods of the MWM test, especially in the mice that had suffered adverse insults in early life. Our findings indicated that prenatal exposure to inflammation or stress exposure in adolescence exacerbated the AISLM and age-related upregulation of Arc and Syt1 expression, and these effects were linked to cognitive impairments in CD-1 mice exposed to adverse factors in early life.

Physical Illnesses Before Diagnosed as Schizophrenia: A Nationwide Case-Control Study

Some physical illnesses are potentially associated with the development of schizophrenia. However, few studies have investigated these associations. Here, we examined physical illnesses and medical utilization patterns existing before patients received a diagnosis of schizophrenia. We enrolled a large representative cohort of the general population in Taiwan (N = 1 000 000) and identified 1969 young patients with a new diagnosis of schizophrenia from January 1, 2000 to December 31, 2013. We conducted a nested case-control study based on risk-set sampling. Each case was age-matched and sex-matched with 4 controls selected from the general population. The case and control groups were compared on the basis of various clinical characteristics. Conditional logistic regression was used to estimate the magnitude of risk associated with newly diagnosed schizophrenia. Within the 1 year before the schizophrenia diagnosis, the cases were most likely to visit the psychiatry department, followed by internal medicine and family medicine departments. According to multivariate analysis, compared with the controls, the cases had substantially higher risk of physical conditions in the prodromal phase, including hypertension (adjusted risk ratio [aRR] = 1.93, P = .001), other forms of heart disease (aRR = 2.07, P < .001), cerebrovascular diseases (aRR = 2.96, P = .001), chronic obstructive pulmonary disease (aRR = 1.50, P = .005), asthma (aRR = 1.76, P = .003), and irritable bowel syndrome (aRR = 2.00, P < .001). A wide range of psychiatric diseases and concomitant use of medications were significantly associated with schizophrenia development. In conclusion, several physical illnesses were identified to be associated with schizophrenia development, indicating that people with these illnesses could be vulnerable to schizophrenia.

Post-pubertal Difference in Nigral Dopaminergic Cells Firing in the Schizophrenia Model Prepared by Perinatal Challenges of a Cytokine, EGF

Schizophrenia in humans typically develops during and after adolescence; however, the biological underpinning for the specificity of this onset time window remains to be determined. In the present study, we investigated this knowledge gap using our own animal model for schizophrenia. Rodents and monkeys challenged with a cytokine, epidermal growth factor (EGF), as neonates are known to exhibit various behavioral and cognitive abnormalities at the post-pubertal stage. We used the EGF-challenged mice as an animal model for schizophrenia to evaluate the electrophysiological impact of this modeling on nigral dopamine neurons before and after puberty. In vivo single unit recording revealed that the burst firing of putative dopamine neurons in substantia nigra pars compacta was significantly higher in the post-pubertal stage of the EGF model than in that of control mice; in contrast, this difference was not observed in the pre-pubertal stage. The increase in burst firing was accompanied by a decline in Ca²⁺-activated K⁺ (I_SK) currents, which influence the firing pattern of dopamine neurons. In vivo local application of the SK channel blocker apamin (80 μM) to the substantia nigra was less effective at increasing burst firing in the EGF model than in control mice, suggesting the pathologic role of the I_SK decrease in this model. Thus, these results suggest that the aberrant post-pubertal hyperactivity of midbrain dopaminergic neurons is associated with the temporal specificity of the behavioral deficit of this model, and support the hypothesis that this dopaminergic aberration could be implicated in the adolescent onset of schizophrenia.

Effects of risperidone on blood levels of interleukin-6 in schizophrenia: A meta-analysis

BACKGROUND

To evaluate the association between risperidone use and interleukin-6 (IL-6) levels by conducting a meta-analysis of controlled before-and-after studies.

METHODS

Studies were identified through a systematic search of PubMed and Embase. The mean and standardized differences were extracted to calculate the standardized mean differences. IL-6 levels were compared in patients with schizophrenia before and after risperidone treatment.

RESULTS

Ten studies were included in the final meta-analysis. The primary findings from our study suggest that there was a significant decrease in serum IL-6 levels after risperidone treatment (P = .021). A subgroup analysis revealed the sources of heterogeneity. The sensitivity analysis indicated that the results were stable, and no publication bias was observed.

CONCLUSIONS

The present meta-analysis provides evidence that risperidone can significantly reduce IL-6 levels in schizophrenia. IL-6 is a potential biomarker of the pathophysiology and clinical processes of schizophrenia.

Effects of inflammation on the kynurenine pathway in schizophrenia - a systematic review

Background

In the last decade, there has been growing evidence that an interaction exists between inflammation and the kynurenine pathway in schizophrenia. Additionally, many authors found microglial activation in cases of schizophrenia due to inflammatory mechanisms related mostly to an increase of pro-inflammatory cytokines. In order to gain new insights into the pathophysiology of schizophrenia, it is important to incorporate the latest published evidence concerning inflammatory mechanisms and kynurenine metabolism. This systematic review aims to collect reliable recent findings within the last decade supporting such a theory.

Methods

A structured search of electronic databases was conducted for publications between 2008 and 2018 to identify eligible studies investigating patients with schizophrenia/psychosis and the relationship between inflammation and kynurenine pathway. Applicable studies were systematically scored using the NIH Quality Assessment Tools. Two researchers independently extracted data on diagnosis (psychosis/schizophrenia), inflammation, and kynurenine/tryptophan metabolites.

Results

Ten eligible articles were identified where seven studies assessed blood samples and three assessed cerebrospinal fluid in schizophrenic patients.

Of these articles:

Four investigated the relationship between immunoglobulins and the kynurenine pathway and found correlations between IgA-mediated responses and levels of tryptophan metabolites (i.e., kynurenine pathway).

Five examined the correlation between cytokines and kynurenine metabolites where three showed a relationship between elevated IL-6, TNF-α concentrations, and the kynurenine pathway.

Only one study discovered correlations between IL-8 and the kynurenine pathway.

Two studies showed correlations with lower concentrations of IL-4 and the kynurenine pathway.

Moreover, this systematic review did not find a significant correlation between CRP (n = 1 study), IFN-γ (n = 3 studies), and the kynurenine pathway in schizophrenia.

Interpretation

These results emphasize how different inflammatory markers can unbalance the tryptophan/kynurenine pathway in schizophrenia. Several tryptophan/kynurenine pathway metabolites are produced which can, in turn, underlie different psychotic and cognitive symptoms via neurotransmission modulation. However, due to heterogeneity and the shortage of eligible articles, they do not robustly converge to the same findings. Hence, we recommend further studies with larger sample sizes to elucidate the possible interactions between the various markers, their blood vs. CSF ratios, and their correlation with schizophrenia symptoms.

Association of peripheral cytokine levels with cerebral structural abnormalities in schizophrenia

A large body of evidence indicates that both the altered cytokines that mediate the immune-inflammatory process and abnormal gray matter are associated with schizophrenia. Whether peripheral cytokines are related to cerebral structural abnormality remains unclear. Therefore, we aimed to investigate the association of peripheral cytokine levels with gray matter abnormalities at the whole brain level in schizophrenia. Forty-four outpatients with schizophrenia and 44 controls were recruited. The serum levels of interleukin-1 beta (IL-1β), IL-2, IL-6, IL-8, interferon-gamma (IFN-γ), transforming growth factor-beta (TGF-β), and IL-10 were measured using a quantitative chemiluminescence assay. High-resolution T1 weighted images were acquired from all subjects and processed using FreeSurfer software to obtain the cortical thickness, surface area, and cortical and subcortical gray matter volumes. The cytokines and cerebral structures were compared between patients and controls using analysis of covariance (ANCOVA). The association between the cytokines and whole cerebral structures was performed using stepwise linear regression. Patients had higher levels of IL-2, IL-6, IL-8, and IL-10 than controls. In patients, the IL-6 level was significantly associated with the cortical thickness in the left pars opercularis, right pars triangularis, left superior temporal gyrus, and right middle temporal gyrus, which showed structural differences between the two groups. Altered cytokine levels may be associated with particular but not all cortical abnormalities in schizophrenia, especially IL-6, which was significantly associated with the abnormal cortical thickness of the bilateral Broca's area and temporal gyrus, which provided neuroimaging evidence to support the relationship between peripheral cytokines and the cerebral cortex in schizophrenia.

Distinct Inflammation Biomarkers in Healthy Individuals and Patients with Schizophrenia: A Reliability Testing of Multiplex Cytokine Immunoassay by Bland-Altman Analysis

OBJECTIVE

Since the inflammatory process has been implicated in the pathophysiology of psychiatric disorder, an important issue emerging is to assess the test-retest reliability of cytokine measurement in healthy individuals and patients with schizophrenia. The objective of the present study was to investigate the test-retest reliability of bead-based multiplex immunoassay technology (BMIT) for cytokine measurement by using a Bland-Altman plot (BAP).

METHODS

Twenty healthy individuals and twenty patients with schizophrenia were enrolled, and a 17-plex cytokine assay was used to measure inflammatory biomarkers at baseline and two weeks later. The test-retest reliability was examined by BAP, 95% limits of agreement (LOA), intraclass correlation coefficient (ICC), and coefficient of repeatability (CoR).

RESULTS

In the healthy controls, only interleukin (IL)-2, IL-13, IL-10, IL-17, and macrophage inflammatory protein-1β showed excellent ICC. The BAP with 95% LOA determined that 13 cytokines showed acceptable 95% LOA for a 2-week test-retest reliability, and only IL-1β, IL-12 and tumor necrosis factor (TNF)-α had significant test-retest bias. The CoR of cytokines varied significantly, ranging from 1.72 to 218.1. Compared with healthy controls, patients with schizophrenia showed significantly higher levels of IL-5, IL-13, and TNF-α and significantly lower levels of IL-4, IL-12, and interferon-gamma (IFN-γ). Of these six cytokines, IL-12 and TNF-α were considered suboptimal reliability.

CONCLUSION

The findings from ICC and CoR implied that the test-retest reliability of BMIT for cytokine measurement were suboptimal. However, the BAP with 95% LOA confirmed that BMIT can reliably distinguish schizophrenia from healthy individuals in cytokine measurement, while significant within-subject variation and between-group overlapping were evident in cytokine expression.

Gut permeability and mimicry of the Glutamate Ionotropic Receptor NMDA type Subunit Associated with protein 1 (GRINA) as potential mechanisms related to a subgroup of people with schizophrenia with elevated antigliadin antibodies (AGA IgG)

About one third of people with schizophrenia have elevated IgG antibodies to gliadin (AGA IgG) and increased inflammation. Understanding the mechanism by which this immune response occurs is critical to the development of personalized treatments. We examined gut permeability and mimicry to the glutamate receptor as possible mechanisms related to high gliadin antibodies (AGA IgG) seen in some people with schizophrenia. The Glutamate Ionotropic Receptor NMDA type Subunit Associated with protein 1 (GRINA) has a similar protein structure to gliadin representing a potential target for cross reactivity or mimicry. In a population of schizophrenia subjects (N = 160) and healthy controls (N = 80) we analyzed serum samples for both GRINA and Anti-Saccharomyces Cerevisiae antibodies (ASCA), related to gut permeability. Schizophrenia patients compared to controls had a higher prevalence of positivity to ASCA IgA (p = 0.004) and IgG (p < 0.001). Multinomial logistic regression showed an association between AGA IgG and ASCA IgG in schizophrenia (p = 0.05 for the estimated regression coefficient) but not in healthy controls (p = 0.13). GRINA IgG was higher in schizophrenia patients than in healthy controls (0.43 ± 0.30 vs. 0.22 ± 0.24, p < 0.001). Logistic regressions showed an association between AGA IgG and GRINA IgG in schizophrenia (p = 0.016 for the estimated regression coefficient) but not for the controls (p = 0.471). Thus, we propose that mimicry through the presence of cross-reactivity between gliadin and GRINA might disrupt the functions of the glutamate system and relate to illness pathophysiology in those with schizophrenia and elevated AGA IgG.

In vitro cytokine synthesis in unstimulated and mitogen-stimulated peripheral blood mononuclear cells from individuals with schizophrenia

Increasing evidence has shown that the immune system is involved in the schizophrenia development, with alterations in immune cell reactivity being one possible factor contributing to its pathogenesis. The purpose of the study was to evaluate in vitro the capability of peripheral blood mononuclear cells (PBMCs) obtained from subjects with schizophrenia and controls to engage in spontaneous and phytohemagglutinin (PHA)-stimulated cytokine production. The concentrations of various cytokines (interleukin (IL)-1β, IL-17A, tumor necrosis factor (TNF), interferon (IFN)-γ and IL-10) in supernatants from cultured PBMCs were measured using the cytometric bead array. No significant differences in the spontaneous production of IL-1β, IL-17A, IFN-γ and IL-10 by PBMCs were detected between individuals with schizophrenia and controls. TNF synthesis by PBMCs was found to be lower among those with schizophrenia. In all subjects and controls, greater cytokine generation was associated with PBMCs treated with PHA compared with those that were not. The PBMCs from people with schizophrenia displayed considerably higher sensitivity to mitogen stimulation, as the production of IL-17A, TNF and IFN-γ was at least threefold of that observed in healthy subjects, which may be driven by antipsychotics taken by patients with schizophrenia. Correlation was observed between spontaneous production of IFN-γ and Positive and Negative Syndrome Scale G subscore (which measures the general symptoms of schizophrenia) and between PHA-stimulated synthesis of IL-17A and G subscore. Our data confirm that the immune system dysregulation may underlie schizophrenia pathophysiology. There is a potential possibility that immunological tests could be used as a diagnostic, therapeutic and side-effects biomarker for schizophrenia, but further studies are needed.

From Infection to the Microbiome: An Evolving Role of Microbes in Schizophrenia

The study of microorganisms such as bacteria, viruses, archaea, fungi, and protozoa in the context of psychiatric disorders may be surprising to some. This intersection of disciplines, however, has a rich history and is currently revitalized by newfound functions of the microbiome and the gut-brain axis in human diseases. Schizophrenia, in particular, fits this model as a disorder with gene and environmental roots that may be anchored in the immune system. In this context, the combination of a precisely timed pathogen exposure in a person with genetically encoded altered immunity may have especially destructive consequences for the central nervous system (CNS). Furthermore, significant components of immunity, such as the development of the immune response and the concept of immune tolerance, are largely dictated by the commensal residents of the microbiome. When this community of microbes is imbalanced, perhaps as the result of a pathogen invasion, stress, or immune gene deficiency, a pathological cycle of localized inflammation, endothelial barrier compromise, translocation of gut-derived products, and systemic inflammation may ensue. If these pathologies enable access of gut and microbial metabolites and immune molecules to the CNS across the blood-brain barrier (BBB), and studies of the gut-brain axis support this hypothesis, a worsening of cognitive deficits and psychiatric symptoms is predicted to occur in susceptible individuals with schizophrenia. In this chapter, we review the role of microbes in various stages of this model and how these organisms may contribute to documented phenotypes of schizophrenia. An increased understanding of the role of pathogens and the microbiome in psychiatric disorders will better guide the development of microbial and immune-based therapeutics for disease prevention and treatment.

Plasma levels of IL-1Ra are associated with schizophrenia

AIM

Although peripheral low-grade inflammation and brain-derived neurotrophic factor (BDNF) levels have been implicated in schizophrenia (SCZ), the interactions between them remain to be fully revealed. We aimed to compare BDNF and cytokines in patients with SCZ and healthy controls (HC). Additionally, we aimed to investigate the association between peripheral levels of cytokines and BDNF in patients with SCZ.

METHODS

Plasma levels of BDNF, interferon gamma, interleukin (IL)-10, IL-12, IL-1, IL-6, IL-8, tumor necrosis factor alpha, macrophage migration inhibitory factor, IL-1 receptor antagonist (IL-1Ra), and CD40 Ligand were compared in 45 SCZ patients and 38 HC using Luminex technology.

RESULTS

Compared to HC, patients had significantly higher IL-1Ra levels (P = 0.031). We found a strong positive association between BDNF and CD40 Ligand in the patient group (rho = 0.858, P < 0.001) as well as in the HC group (rho = 0.822, P < 0.001), respectively. Furthermore, there was a negative association between BDNF and tumor necrosis factor alpha in patients (rho = -0.429, P = 0.030) as well as in HC (rho = -0.649, P < 0.001).

CONCLUSION

These results suggest that the cytokine IL-1Ra may play a role in SCZ pathophysiology. Additionally, the interaction between cytokines and BDNF levels further indicated the diverse actions of these cytokines.

Proinflammatory and anti-inflammatory biomarkers in schizophrenia and influence of simvastatin on the interleukin-6

The present study sought to assess biomarkers of inflammation in stable patients with schizophrenia (SZ) on clozapine therapy. We recruited 60 outpatients with SZ and 60 healthy controls, matched for sex and age. Compared with controls, patients had significantly increased concentrations of interleukin-6 and tumor necrosis factor-α. Interestingly, patients on simvastatin had lower interleukin-6 levels compared with patients not on simvastatin and controls. This study corroborated previous evidence for increased inflammatory biomarkers in SZ and detected a potential anti-inflammatory action of simvastatin in patients with a clinical diagnosis of SZ on clozapine therapy.

Complement system biomarkers in first episode psychosis

Several lines of evidence implicate immunological/inflammatory factors in development of schizophrenia. Complement is a key driver of inflammation, and complement dysregulation causes pathology in many diseases. Here we explored whether complement dysregulation occurred in first episode psychosis (FEP) and whether this provides a source of biomarkers. Eleven complement analytes (C1q, C3, C4, C5, factor B [FB], terminal complement complex [TCC], factor H [FH], FH-related proteins [FHR125], Properdin, C1 inhibitor [C1inh], soluble complement receptor 1 [CR1]) plus C-reactive protein (CRP) were measured in serum from 136 first episode psychosis (FEP) cases and 42 mentally healthy controls using established in-house or commercial ELISA. The relationship between caseness and variables (analytes measured, sex, age, ethnicity, tobacco/cannabis smoking) was tested by multivariate logistic regression. When measured individually, only TCC was significantly different between FEP and controls (p=0.01). Stepwise selection demonstrated interdependence between some variables and revealed other variables that significantly and independently contributed to distinguishing cases and controls. The final model included demographics (sex, ethnicity, age, tobacco smoking) and a subset of analytes (C3, C4, C5, TCC, C1inh, FHR125, CR1). A receiver operating curve analysis combining these variables yielded an area under the curve of 0.79 for differentiating FEP from controls. This model was confirmed by multiple replications using randomly selected sample subsets. The data suggest that complement dysregulation occurs in FEP, supporting an underlying immune/inflammatory component to the disorder. Classification of FEP cases according to biological variables rather than symptoms would help stratify cases to identify those that might most benefit from therapeutic modification of the inflammatory response.

Expression and Function of IL-33/ST2 Axis in the Central Nervous System Under Normal and Diseased Conditions

Interleukin-33 (IL-33) is a well-recognized immunomodulatory cytokine which plays critical roles in tissue function and immune-mediated diseases. The abundant expression of IL-33 in brain and spinal cord prompted many scientists to explore its unique role in the central nervous system (CNS) under physiological and pathological conditions. Indeed emerging evidence from over a decade's research suggests that IL-33 acts as one of the key molecular signaling cues coordinating the network between the immune and CNS systems, particularly during the development of neurological diseases. Here, we highlight the recent advances in our knowledge regarding the distribution and cellular localization of IL-33 and its receptor ST2 in specific CNS regions, and more importantly the key roles IL-33/ST2 signaling pathway play in CNS function under normal and diseased conditions.

Plasma cytokines in minimally treated schizophrenia

In schizophrenia, plasma cytokines abnormalities offer vital support for immunopathogenetic basis. However, most of the previous studies on plasma cytokines are confounded by examination of antipsychotic-treated schizophrenia patients. In this study, we examined a large sample of antipsychotic-naïve/free schizophrenia patients (N = 75) in comparison with healthy controls (N = 102). Plasma cytokines (Interleukins ([IL] 2, 4, 6, 10, 17), Tumor necrosis factor [TNF] and Interferon gamma [IFN-g]) were assessed using cytometric bead array assay. Schizophrenia patients showed significantly greater levels of IL-6 and lower levels of IL-17 as well as IFN-g in comparison to healthy controls. However, after taking censoring into account and adjusting for potential confounders (sex, age, BMI and smoking), only IL-6 was found to be elevated in patients. Cytokine profile showed differential and pathogenetically relevant correlation with clinical symptoms. Together, these observations offer further support to immunological component in schizophrenia pathogenesis.

Molecular mechanisms involved in epidermal growth factor receptor-mediated inhibition of dopamine D3 receptor signaling

The phenomenon wherein the signaling by a given receptor is regulated by a different class of receptors is termed transactivation or crosstalk. Crosstalk between receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs) is highly diverse and has unique functional implications because of the distinct structural features of the receptors and the signaling pathways involved. The present study used the epidermal growth factor receptor (EGFR) and dopamine D₃ receptor (D₃R), which are both associated with schizophrenia, as the model system to study crosstalk between RTKs and GPCRs. Loss-of-function approaches were used to identify the cellular components involved in the tyrosine phosphorylation of G protein-coupled receptor kinase 2 (GRK2), which is responsible for EGFR-induced regulation of the functions of D₃R. SRC proto-oncogene (Src, non-receptor tyrosine kinase), heterotrimeric G protein Gβγ subunit, and endocytosis of EGFR were involved in the tyrosine phosphorylation of GRK2. In response to EGF treatment, Src interacted with EGFR in a Gβγ-dependent manner, resulting in the endocytosis of EGFR. Internalized EGFR in the cytosol mediated Src/Gβγ-dependent tyrosine phosphorylation of GRK2. The binding of tyrosine-phosphorylated GRK2 to the T142 residue of D₃R resulted in uncoupling from G proteins, endocytosis, and lysosomal downregulation. This study identified the molecular mechanisms involved in the EGFR-mediated regulation of the functions of D₃R, which can be extended to the crosstalk between other RTKs and GPCRs.

Procalcitonin and C - reactive protein as peripheral inflammatory markers in antipsychotic drug-free schizophrenia patients

Inflammation is considered to be relevant in pathophysiology of schizophrenia. Existing literature indicates that controlling inflammation may be helpful in patient management. Procalcitonin (PCT) is an established marker of inflammation which has not been well studied in context with schizophrenia. The study recruited 34 schizophrenia patients free of antipsychotic treatment and 24 healthy controls without any signs of inflammation. Plasma C reactive protein was quantified using a high sensitivity turbidimetric assay. Plasma PCT levels was estimated by sandwich ELISA. The study ruled out autoimmune antibodies by ANA and RF tests which exclude confounding factors contributing to inflammation. The data shows a subgroup of patients 17/34 (50%) have either elevated PCT or CRP levels. This study is the first to report PCT values in antipsychotic drug-free patients with schizophrenia.

Development and Evaluation of a Preoperative Risk Calculator for Periprosthetic Joint Infection Following Total Joint Arthroplasty

BACKGROUND

Preoperative identification of patients at risk for periprosthetic joint infection (PJI) following total hip arthroplasty (THA) or total knee arthroplasty (TKA) is important for patient optimization and targeted prevention. The purpose of this study was to create a preoperative PJI risk calculator for assessing a patient's individual risk of developing (1) any PJI, (2) PJI caused by Staphylococcus aureus, and (3) PJI caused by antibiotic-resistant organisms.

METHODS

A retrospective review was performed of 27,717 patients (12,086 TKAs and 31,167 THAs), including 1,035 with confirmed PJI, who were treated at a single institution from 2000 to 2014. A total of 42 risk factors, including patient characteristics and surgical variables, were evaluated with a multivariate analysis in which coefficients were scaled to produce integer scores. External validation was performed with use of data on 29,252 patients who had undergone total joint arthroplasty (TJA) at an independent institution.

RESULTS

Of the 42 risk factors studied, 25 were found not to be significant risk factors for PJI. The most influential of the remaining 17 included a previous open surgical procedure, drug abuse, a revision procedure, and human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS). The areas under the curves were 0.83 and 0.84 for any PJI, 0.86 and 0.83 for antibiotic-resistant PJI, and 0.86 and 0.73 for S. aureus PJI in the internal and external validation models, respectively. The rates of PJI were 0.56% and 0.61% in the lowest decile of risk scores and 15.85% and 20.63% in the highest decile.

CONCLUSIONS

In this large-cohort study, we were able to identify and validate risk factors and their relative weights for predicting PJI. Factors such as prior surgical procedures and high-risk comorbidities should be considered when determining whether TJA is indicated and when counseling patients.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Increased Complications for Schizophrenia and Bipolar Disorder Patients Undergoing Total Joint Arthroplasty

BACKGROUND

Although it has been shown that anxiety and depression are associated with increased complications after total joint arthroplasty (TJA), the outcomes of TJA in patients with a history of psychosis are unknown. This study evaluated the influence of bipolar and schizophrenic disorders on complications after TJA, particularly aseptic and septic revisions.

METHODS

A retrospective review of 156 TJAs (125 primaries and 31 revisions) was performed at a single institution from 2000 to 2015. Bipolar and schizophrenic patients were identified based on International Classification of Diseases, Ninth Revision codes or by those actively taking anti-psychotic medications, followed by manual chart review to confirm diagnoses. The psychosis patient cohort was matched 3:1 for a variety of factors. Revisions and readmissions were evaluated. Survivorship curves were generated.

RESULTS

Patients with schizophrenia or bipolar disorder had an increased odds of developing peri-prosthetic joint infection at 90 days (odds ratio [OR] 3.34, P = .049), 2 years (OR 3.94, P = .004), and at any time point (OR 4.32, P = .002). Psychosis patients had increased odds of aseptic and mechanical revisions at all endpoints, particularly from dislocation. Psychosis patients had a higher number of post-operative emergency department visits (P < .001), and were more likely to be discharged to a rehabilitation facility (P < .001).

CONCLUSIONS

Patients with bipolar affective disorder or schizophrenia may have multiple barriers to self-care after TJA, and are at an increased risk for undergoing revision TJA for prosthetic joint infection and mechanical causes. Increased pre-operative education and screening of this patient population may be necessary prior to performing TJA.

Increased serum levels and promoter polymorphisms of macrophage migration inhibitory factor in schizophrenia

BACKGROUND

Numerous studies have suggested that an immune system imbalance plays an important role in schizophrenia. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine. It plays multiple roles in various biological processes, including inflammation and neurogenesis. Furthermore, several exhaustive serum proteomic profiling studies have identified MIF as a potential biomarker of schizophrenia. Here, we investigate MIF protein levels in serum and postmortem prefrontal cortex in patients with schizophrenia and controls. Moreover, we investigate the association of two functional polymorphisms in the MIF gene promoter region (MIF-794CATT_5-8 microsatellite and MIF-173G/C single-nucleotide polymorphism [SNP]) with schizophrenia.

METHODS

We measured serum MIF levels with an enzyme-linked immunosorbent assay (ELISA) (51 patients vs. 86 controls) and postmortem brain MIF levels with a western blotting assay (18 patients vs. 22 controls). Subsequently, we genotyped the MIF-794CATT_5-8 microsatellite with a fluorescence-based fragment assay and the MIF-173G/C SNP with a TaqMan SNP genotyping assay (1483 patients vs. 1454 controls).

RESULTS

Serum MIF levels were significantly higher in patients with schizophrenia than in controls (p=0.00118), and were positively correlated with antipsychotic dose (Spearman's r=0.222, p=0.0402). In addition, an earlier age of onset was observed in patients with a high serum MIF level (≥40ng/mL) than those with a low serum MIF level (<40ng/mL) (p=0.0392). However, postmortem brain MIF levels did not differ between patients with schizophrenia and controls. The association study revealed that the CATT₆-G haplotype was nominally significantly associated with schizophrenia (p=0.0338), and that the CATT₆ allele and CATT₆-G haplotype were significantly associated with female adolescent-onset schizophrenia (AsOS) (corrected p=0.0222 and p=0.0147, respectively).

CONCLUSIONS

These results suggest that serum MIF level is a potential pharmacodynamic and/or monitoring marker of schizophrenia, and is related to a novel antipsychotic effect beyond dopamine antagonism. Furthermore, the MIF gene polymorphisms are associated with the risk for schizophrenia especially in adolescent females, and are potential stratification markers of schizophrenia. Further studies of MIF are warranted to elucidate the pathophysiology of schizophrenia and the effects of antipsychotics.