Prenatal inflammation and risk for schizophrenia: A role for immune proteins in neurodevelopment

Pioglitazone attenuates behavioral and electrophysiological dysfunctions induced by two-hit model of schizophrenia in adult rodent offspring

Maternal infection and stress exposure, especially during childhood and adolescence, have been implicated as risk factors for schizophrenia. Both insults induce an exacerbated inflammatory response, which could mediate disturbance of neurodevelopmental processes and, ultimately, malfunctioning of neural systems observed in this disorder. Thus, anti-inflammatory drugs, such as PPARγ agonists, may potentially be used to prevent the development of schizophrenia. Microglia culture was prepared from the offspring of saline or poly(I:C)-injected mice. The cells were pretreated with pioglitazone and then, stimulated by LPS. Proinflammatory mediators and phagocytic activity were measured. Also, pregnant rats were injected with saline or poly(I:C) on GD17. The offspring were subjected to footshock during adolescence and subsequently injected with pioglitazone or vehicle. At adulthood, behavior and dopaminergic activity were evaluated. Pioglitazone reduced proinflammatory mediators induced by poly(I:C) microglia stimulated by LPS without affecting their decreased phagocytic activity. The PPARγ agonist also prevented the emergence of social and cognitive impairments, as well as attenuated the increased number of spontaneously active dopamine neurons in the VTA, observed in both males and females from poly(I:C) and stress group. Therefore, pioglitazone could potentially prevent the emergence of the schizophrenia-like alterations induced by the two-hit model via reduction of microglial activation.

The Interrelationships between Cytokines and Schizophrenia: A Systematic Review

Schizophrenia (SCZ) imposes a significant burden on patients and their families because of its high prevalence rate and disabling nature. Given the lack of definitive conclusions regarding its pathogenesis, physicians heavily rely on patients' subjective symptom descriptions for diagnosis because reliable diagnostic biomarkers are currently unavailable. The role of the inflammatory response in the pathogenesis of SCZ has been supported by some studies. The findings of these studies showed abnormal changes in the levels of inflammatory factors, such as cytokines (CKs), in both peripheral blood and cerebrospinal fluid (CSF) among individuals affected by SCZ. The findings imply that inflammatory factors could potentially function as risk indicators for the onset of SCZ. Consequently, researchers have directed their attention towards investigating the potential utility of CKs as viable biomarkers for diagnosing SCZ. Extracellular vesicles (EVs) containing disease-specific components exhibit remarkable stability and abundance, making them promising candidates for biomarker discovery across various diseases. CKs encapsulated within EVs secreted by immune cells offer valuable insights into disease progression. This review presents a comprehensive analysis summarizing the relationship between CKs and SCZ and emphasizes the vital role of CKs encapsulated within EVs in the pathogenesis and development of SCZ.

The neutrophil-lymphocyte ratio in first-episode medication-naïve patients with schizophrenia: A 12-week longitudinal follow-up study

Inflammation has been related to schizophrenia (SZ). The neutrophil-to-lymphocyte ratio (NLR) is an inexpensive inflammatory marker, however, its potential predictive value in patients with SZ has not been extensively investigated. This study aimed to examine whether NLR could predict the clinical response to antipsychotics in this population. One hundred and ninety-five medication-naïve first-episode schizophrenia (MNFES) patients were recruited and received treatment with risperidone for 12 weeks in the present study. Clinical symptoms were evaluated at week 0 and the end of 12 weeks of treatment using the PANSS scales. Complete blood counts were determined at baseline. We found that baseline NEU counts and NLR were positively associated with improvements in clinical symptoms in patients. In addition, MNFES patients with higher baseline NLR values showed a better treatment response to antipsychotics. Linear regression analysis revealed a predictive role of baseline NLR for the improvements of clinical symptoms in SZ patients. Our findings demonstrate that higher NLR was related to better improvements in symptoms after 12 weeks of treatment with antipsychotics, which renders it a promising biomarker of the response to antipsychotics in clinical practice.

Complex Neuroimmune Involvement in Neurodevelopment: A Mini-Review

It is increasingly evident that cells and molecules of the immune system play significant roles in neurodevelopment. As perinatal infection is associated with the development of neurodevelopmental disorders, previous research has focused on demonstrating that the induction of neuroinflammation in the developing brain is capable of causing neuropathology and behavioral changes. Recent studies, however, have revealed that immune cells and molecules in the brain can influence neurodevelopment without the induction of overt inflammation, identifying neuroimmune activities as integral parts of normal neurodevelopment. This mini-review describes the shift in literature that has moved from emphasizing the intrusion of inflammatory events as a main culprit of neurodevelopmental disorders to evaluating the deviation of the normal neuroimmune activities in neurodevelopment as a potential pathogenic mechanism.

De novo mutations disturb early brain development more frequently than common variants in schizophrenia

Investigating functional, temporal, and cell-type expression features of mutations is important for understanding a complex disease. Here, we collected and analyzed common variants and de novo mutations (DNMs) in schizophrenia (SCZ). We collected 2,636 missense and loss-of-function (LoF) DNMs in 2,263 genes across 3,477 SCZ patients (SCZ-DNMs). We curated three gene lists: (a) SCZ-neuroGenes (159 genes), which are intolerant to LoF and missense DNMs and are neurologically important, (b) SCZ-moduleGenes (52 genes), which were derived from network analyses of SCZ-DNMs, and (c) SCZ-commonGenes (120 genes) from a recent GWAS as reference. To compare temporal gene expression, we used the BrainSpan dataset. We defined a fetal effect score (FES) to quantify the involvement of each gene in prenatal brain development. We further employed the specificity indexes (SIs) to evaluate cell-type expression specificity from single-cell expression data in cerebral cortices of humans and mice. Compared with SCZ-commonGenes, SCZ-neuroGenes and SCZ-moduleGenes were highly expressed in the prenatal stage, had higher FESs, and had higher SIs in fetal replicating cells and undifferentiated cell types. Our results suggested that gene expression patterns in specific cell types in early fetal stages might have impacts on the risk of SCZ during adulthood.

Baroreflex sensitivity is associated with markers of hippocampal gliosis and dysmyelination in patients with psychosis

PURPOSE

Hippocampal dysfunction plays a key role in the pathology of psychosis. Given hippocampal sensitivity to changes in cerebral perfusion, decreased baroreflex function could contribute to psychosis pathogenesis. This study had two aims: (1) To compare baroreflex sensitivity in participants with psychosis to two control groups: participants with a nonpsychotic affective disorder and participants with no history of psychiatric disease; (2) to examine the relationship between hippocampal neurometabolites and baroreflex sensitivities in these three groups. We hypothesized that baroreflex sensitivity would be reduced and correlated with hippocampal neurometabolite levels in participants with psychosis, but not in the control groups.

METHODS

We assessed baroreflex sensitivity during the Valsalva maneuver separated into vagal and adrenergic components. Metabolite concentrations for cellular processes were quantitated in the entire multivoxel hippocampus using H¹-MR spectroscopic (MRS) imaging and were compared with baroreflex sensitivities in the three groups.

RESULTS

Vagal baroreflex sensitivity (BRS-V) was reduced in a significantly larger proportion of participants with psychosis compared with patients with nonpsychotic affective disorders, whereas participants with psychosis had increased adrenergic baroreflex sensitivity (BRS-A) compared with participants with no history of psychiatric disease. Only in psychotic cases were baroreflex sensitivities associated with hippocampal metabolite concentrations. Specifically, BRS-V was inversely correlated with myo-inositol, a marker of gliosis, and BRS-A was positively correlated with energy dependent dysmyelination (choline, creatine) and excitatory activity (GLX).

CONCLUSIONS

Abnormal baroreflex sensitivity is common in participants with psychosis and is associated with MRS markers of hippocampal pathology. Future longitudinal studies are needed to examine causality.

Analysis of the association between MICA gene polymorphisms and schizophrenia

BACKGROUND

The major histocompatibility complex (MHC) has been implicated in schizophrenia. This study aimed to explore the correlation between the major histocompatibility complex class I polypeptide-related sequence A (MICA) polymorphisms and schizophrenia.

METHODS

A total of 220 Han schizophrenia patients, 47 Han healthy controls, 155 Li schizophrenia patients, and 48 Li controls were selected from Hainan Province, China. The diagnosis was made according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, criteria. Sequencing-based-typing (PCR-SBT) technology was used for MICA allele typing, and the correlation analyses of MICA gene polymorphism and schizophrenia were performed.

RESULTS

In the Han group, the three allele frequencies of MICA*002:01, MICA*A4, and MICA*A9 in the schizophrenia group were significantly higher than those in the healthy control group, and the differences were statistically significant (pc < 0.05; pc values were 0.024, 0.030, and 0.031, respectively). Yet, there was no difference in the MICA gene between the schizophrenia group and the healthy controls group in the Li population.

CONCLUSION

We found MICA*002:01, MICA*A4, and MICA*A9 may be susceptibility alleles for schizophrenia in the Han population, while the MICA allele polymorphism in the Li population is not associated with schizophrenia in Chinese.

Spironolactone alleviates schizophrenia-related reversal learning in Tcf4 transgenic mice subjected to social defeat

Cognitive deficits are a hallmark of schizophrenia, for which no convincing pharmacological treatment option is currently available. Here, we tested spironolactone as a repurposed compound in Tcf4 transgenic mice subjected to psychosocial stress. In this ‘2-hit’ gene by environment mouse (GxE) model, the animals showed schizophrenia-related cognitive deficits. We had previously shown that spironolactone ameliorates working memory deficits and hyperactivity in a mouse model of cortical excitatory/inhibitory (E/I) dysbalance caused by an overactive NRG1-ERBB4 signaling pathway. In an add-on clinical study design, we used spironolactone as adjuvant medication to the standard antipsychotic drug aripiprazole. We characterized the compound effects using our previously established Platform for Systematic Semi-Automated Behavioral and Cognitive Profiling (PsyCoP). PsyCoP is a widely applicable analysis pipeline based on the Research Domain Criteria (RDoC) framework aiming at facilitating translation into the clinic. In addition, we use dimensional reduction to analyze and visualize overall treatment effect profiles. We found that spironolactone and aripiprazole improve deficits of several cognitive domains in Tcf4tg x SD mice but partially interfere with each other’s effect in the combination therapy. A similar interaction was detected for the modulation of novelty-induced activity. In addition to its strong activity-dampening effects, we found an increase in negative valence measures as a side effect of aripiprazole treatment in mice. We suggest that repurposed drug candidates should first be tested in an adequate preclinical setting before initiating clinical trials. In addition, a more specific and effective NRG1-ERBB4 pathway inhibitor or more potent E/I balancing drug might enhance the ameliorating effect on cognition even further.

Prenatal infection and schizophrenia: A decade of further progress

Epidemiologic studies have provided evidence that prenatal exposure to maternal infection is associated with an increased risk of developing schizophrenia in the offspring. Research over the past decade has added further to our understanding of the role of prenatal infection in schizophrenia risk. These investigations include several well-powered designs, and like some earlier studies, measured maternal antibodies to specific infectious agents in stored serum samples and large registers to identify clinically diagnosed infections during pregnancy. Convergent findings from antibody studies suggest that prenatal maternal infection with Toxoplasma gondii is associated with increased schizophrenia risk in the offspring, while associations with HSV-2 infection are likely attributable to confounding. Maternal influenza infection remains a viable candidate for schizophrenia, based on an early serological study, though there has been only one attempt to replicate this finding, with a differing methodology. A prior association between maternal serologically confirmed cytomegalovirus infections require further study. Clinically diagnosed maternal infection, particularly bacterial infection, also appears to be associated with increased risk of offspring schizophrenia, and heterogeneity in these findings is likely due to methodological differences between studies. Further clarification may be provided by future studies that address the timing, type, and clinical features of infections. Important insight may be gained by examining the long-term offspring outcomes in emerging epidemics such as Zika virus and COVID-19, and by investigating the interaction between exposure to prenatal infection and other risk or protective factors.

Structural and Functional Deviations of the Hippocampus in Schizophrenia and Schizophrenia Animal Models

Schizophrenia is a grave neuropsychiatric disease which frequently onsets between the end of adolescence and the beginning of adulthood. It is characterized by a variety of neuropsychiatric abnormalities which are categorized into positive, negative and cognitive symptoms. Most therapeutical strategies address the positive symptoms by antagonizing D2-dopamine-receptors (DR). However, negative and cognitive symptoms persist and highly impair the life quality of patients due to their disabling effects. Interestingly, hippocampal deviations are a hallmark of schizophrenia and can be observed in early as well as advanced phases of the disease progression. These alterations are commonly accompanied by a rise in neuronal activity. Therefore, hippocampal formation plays an important role in the manifestation of schizophrenia. Furthermore, studies with animal models revealed a link between environmental risk factors and morphological as well as electrophysiological abnormalities in the hippocampus. Here, we review recent findings on structural and functional hippocampal abnormalities in schizophrenic patients and in schizophrenia animal models, and we give an overview on current experimental approaches that especially target the hippocampus. A better understanding of hippocampal aberrations in schizophrenia might clarify their impact on the manifestation and on the outcome of this severe disease.

The Complement System in the Central Nervous System: From Neurodevelopment to Neurodegeneration

The functions of the complement system to both innate and adaptive immunity through opsonization, cell lysis, and inflammatory activities are well known. In contrast, the role of complement in the central nervous system (CNS) which extends beyond immunity, is only beginning to be recognized as important to neurodevelopment and neurodegeneration. In addition to protecting the brain against invasive pathogens, appropriate activation of the complement system is pivotal to the maintenance of normal brain function. Moreover, overactivation or dysregulation may cause synaptic dysfunction and promote excessive pro-inflammatory responses. Recent studies have provided insights into the various responses of complement components in different neurological diseases and the regulatory mechanisms involved in their pathophysiology, as well as a glimpse into targeting complement factors as a potential therapeutic modality. However, there remain significant knowledge gaps in the relationship between the complement system and different brain disorders. This review summarizes recent key findings regarding the role of different components of the complement system in health and pathology of the CNS and discusses the therapeutic potential of anti-complement strategies for the treatment of neurodegenerative conditions.

Association between TLR2 polymorphisms (- 196-174 Ins/Del, R677W, R753Q, and P631H) and schizophrenia in a Tunisian population

Since immune dysregulation has been well studied in schizophrenia pathophysiology, recent studies showed a potent role of TLR2 in neuroinflammation process underlying schizophrenia pathogenesis. However, the genetic predisposition is still unclear. Thus, we hypothesized that TLR2 polymorphisms - 196-174 Ins/Del (rs111200466), R753Q (rs5743708), R677W (rs121917864), and P631H (rs5743704) could be involved in schizophrenia predisposition. A case-control study was performed on a Tunisian population composed of 250 healthy controls and 250 patients genotyped by PCR-RFLP. Genotype and allele distribution were evaluated with sex, schizophrenia subtypes, and other clinical features. We also assessed a haplotype analysis for TLR2 polymorphisms with schizophrenia. Our results showed higher ins/del genotype frequency in healthy women compared to patients (p = 0.006; OR = 0.2). In the other hand, logistic regression showed higher ins/del genotype frequency in controls compared to paranoid patients (p = 0.05; OR = 0.48, adjusted). Frequencies of CT and T allele of R677W were significantly higher in patients compared to controls (p < 10^-4, OR = 10.39; p < 10^-4, OR = 4, adjusted, respectively). R753Q polymorphism was exclusively detected in patients (GA + AA = 2.5%) particularly in men with disorganized subtype. P631H did not show any association with schizophrenia. Finally, haplotype analysis showed that InsGTC and delGTC were associated with higher risk of schizophrenia (p = 0.0001, OR = 8.58; p = 0.04, OR = 5.01, respectively). In the Tunisian population, our results suggested that TLR2 R677W could be associated with susceptibility for schizophrenia, while - 196-174 Ins/Del suggested a trend of protection in women. Otherwise, R753Q could have an effect on schizophrenia especially for disorganized subgroup.

Histamine, Neuroinflammation and Neurodevelopment: A Review

The biogenic amine, histamine, has been shown to critically modulate inflammatory processes as well as the properties of neurons and synapses in the brain, and is also implicated in the emergence of neurodevelopmental disorders. Indeed, a reduction in the synthesis of this neuromodulator has been associated with the disorders Tourette's syndrome and obsessive-compulsive disorder, with evidence that this may be through the disruption of the corticostriatal circuitry during development. Furthermore, neuroinflammation has been associated with alterations in brain development, e.g., impacting synaptic plasticity and synaptogenesis, and there are suggestions that histamine deficiency may leave the developing brain more vulnerable to proinflammatory insults. While most studies have focused on neuronal sources of histamine it remains unclear to what extent other (non-neuronal) sources of histamine, e.g., from mast cells and other sources, can impact brain development. The few studies that have started exploring this in vitro, and more limited in vivo, would indicate that non-neuronal released histamine and other preformed mediators can influence microglial-mediated neuroinflammation which can impact brain development. In this Review we will summarize the state of the field with regard to non-neuronal sources of histamine and its impact on both neuroinflammation and brain development in key neural circuits that underpin neurodevelopmental disorders. We will also discuss whether histamine receptor modulators have been efficacious in the treatment of neurodevelopmental disorders in both preclinical and clinical studies. This could represent an important area of future research as early modulation of histamine from neuronal as well as non-neuronal sources may provide novel therapeutic targets in these disorders.

Childhood disadvantage, neurocognitive development and neuropsychiatric disorders: Evidence of mechanisms

PURPOSE OF REVIEW

Children living in socioeconomically disadvantaged households have excess risks of neurodevelopmental and neuropsychiatric problems. The purpose of this review is to synthesize evidence for mechanisms that may contribute to these excess risks.

RECENT FINDINGS

The majority of the 60 studies included in our review focused on children's neurocognitive development and behavioural problems. About half conducted mediation analyses of factors in the family and neighbourhood environments, including access to resources (e.g. cognitive inputs within the home environment) and exposure to stressors (e.g. negative parenting practices), as well as neurobiological embedding of childhood disadvantage. In addition, many studies conducted moderation analyses of factors that were hypothesized to interact with (i.e. exacerbate or mitigate) the harmful effects of childhood disadvantage.

SUMMARY

Many of the factors that contribute to the excess risk of neurodevelopmental and neuropsychiatric problems among children in disadvantaged households are potentially modifiable (e.g. cognitively stimulating materials, parental language input, cultural resources, parental stress and psychopathology, negative parenting, neighbourhood violence). If their causality is ultimately established, they could be targets for the prevention and reduction of disparities. The continued search for mechanisms should not detract from work to reduce and hopefully eliminate children's exposure to disadvantage.

Contribution of Pro-Inflammatory Molecules Induced by Respiratory Virus Infections to Neurological Disorders

Neurobehavioral alterations and cognitive impairment are common phenomena that represent neuropsychiatric disorders and can be triggered by an exacerbated immune response against pathogens, brain injury, or autoimmune diseases. Pro-inflammatory molecules, such as cytokines and chemokines, are produced in the brain by resident cells, mainly by microglia and astrocytes. Brain infiltrating immune cells constitutes another source of these molecules, contributing to an impaired neurological synapse function, affecting typical neurobehavioral and cognitive performance. Currently, there is increasing evidence supporting the notion that behavioral alterations and cognitive impairment can be associated with respiratory viral infections, such as human respiratory syncytial virus, influenza, and SARS-COV-2, which are responsible for endemic, epidemic, or pandemic outbreak mainly in the winter season. This article will review the brain′s pro-inflammatory response due to infection by three highly contagious respiratory viruses that are the leading cause of acute respiratory illness, morbidity, and mobility in infants, immunocompromised and elderly population. How these respiratory viral pathogens induce increased secretion of pro-inflammatory molecules and their relationship with the alterations at a behavioral and cognitive level will be discussed.

Metabolic Flexibility Assists Reprograming of Central and Peripheral Innate Immunity During Neurodevelopment

Central innate immunity assists time-dependent neurodevelopment by recruiting and interacting with peripheral immune cells. Microglia are the major player of central innate immunity integrating peripheral signals arising from the circumventricular regions lacking the blood-brain barrier (BBB), via neural afferent pathways such as the vagal nerve and also by choroid plexus into the brain ventricles. Defective and/or unrestrained activation of central and peripheral immunity during embryonic development might set an aberrant connectome establishment and brain function, leading to major psychiatric disorders in postnatal stages. Molecular candidates leading to central and peripheral innate immune overactivation identified metabolic substrates and lipid species as major contributors of immunological priming, supporting the role of a metabolic flexibility node during trained immunity. Mechanistically, trained immunity is established by an epigenetic program including DNA methylation and histone acetylation, as the major molecular epigenetic signatures to set immune phenotypes. By definition, immunological training sets reprogramming of innate immune cells, enhancing or repressing immune responses towards a second challenge which potentially might contribute to neurodevelopment disorders. Notably, the innate immune training might be set during pregnancy by maternal immune activation stimuli. In this review, we integrate the most valuable scientific evidence supporting the role of metabolic cues assisting metabolic flexibility, leading to innate immune training during development and its effects on aberrant neurological phenotypes in the offspring. We also add reports supporting the role of methylation and histone acetylation signatures as a major epigenetic mechanism regulating immune training.

PsyCoP - A Platform for Systematic Semi-Automated Behavioral and Cognitive Profiling Reveals Gene and Environment Dependent Impairments of Tcf4 Transgenic Mice Subjected to Social Defeat

Recently, hundreds of risk genes associated with psychiatric disorders have been identified. These are thought to interact with environmental stress factors in precipitating pathological behaviors. However, the individual phenotypes resulting from specific genotype by environment (G×E) interactions remain to be determined. Toward a more systematic approach, we developed a novel standardized and partially automatized platform for systematic behavioral and cognitive profiling (PsyCoP). Here, we assessed the behavioral and cognitive disturbances in Tcf4 transgenic mice (Tcf4tg) exposed to psychosocial stress by social defeat during adolescence using a "two-hit" G×E mouse model. Notably, TCF4 has been repeatedly identified as a candidate risk gene for different psychiatric diseases and Tcf4tg mice display behavioral endophenotypes such as fear memory impairment and hyperactivity. We use the Research Domain Criteria (RDoC) concept as framework to categorize phenotyping results in a translational approach. We propose two methods of dimension reduction, clustering, and visualization of behavioral phenotypes to retain statistical power and clarity of the overview. Taken together, our results reveal that sensorimotor gating is disturbed by Tcf4 overexpression whereas both negative and positive valence systems are primarily influenced by psychosocial stress. Moreover, we confirm previous reports showing that deficits in the cognitive domain are largely dependent on the interaction between Tcf4 and psychosocial stress. We recommend that the standardized analysis and visualization strategies described here should be applied to other two-hit mouse models of psychiatric diseases and anticipate that this will help directing future preclinical treatment trials.

Evidence in cortical folding patterns for prenatal predispositions to hallucinations in schizophrenia

All perception is a construction of the brain from sensory input. Our first perceptions begin during gestation, making fetal brain development fundamental to how we experience a diverse world. Hallucinations are percepts without origin in physical reality that occur in health and disease. Despite longstanding research on the brain structures supporting hallucinations and on perinatal contributions to the pathophysiology of schizophrenia, what links these two distinct lines of research remains unclear. Sulcal patterns derived from structural magnetic resonance (MR) images can provide a proxy in adulthood for early brain development. We studied two independent datasets of patients with schizophrenia who underwent clinical assessment and 3T MR imaging from the United Kingdom and Shanghai, China (n = 181 combined) and 63 healthy controls from Shanghai. Participants were stratified into those with (n = 79 UK; n = 22 Shanghai) and without (n = 43 UK; n = 37 Shanghai) hallucinations from the PANSS P3 scores for hallucinatory behaviour. We quantified the length, depth, and asymmetry indices of the paracingulate and superior temporal sulci (PCS, STS), which have previously been associated with hallucinations in schizophrenia, and constructed cortical folding covariance matrices organized by large-scale functional networks. In both ethnic groups, we demonstrated a significantly shorter left PCS in patients with hallucinations compared to those without, and to healthy controls. Reduced PCS length and STS depth corresponded to focal deviations in their geometry and to significantly increased covariance within and between areas of the salience and auditory networks. The discovery of neurodevelopmental alterations contributing to hallucinations establishes testable models for these enigmatic, sometimes highly distressing, perceptions and provides mechanistic insight into the pathological consequences of prenatal origins.

Poly I:C-induced maternal immune challenge reduces perineuronal net area and raises spontaneous network activity of hippocampal neurons in vitro

Activation of the maternal immune system (MIA) during gestation is linked to neuropsychiatric diseases like schizophrenia. While many studies address behavioural aspects, less is known about underlying cellular mechanisms. In the following study, BALB/c mice received intraperitoneal injections of polyinosinic-polycytidylic acid (Poly I:C) (20 µg/ml) or saline (0.9%) at gestation day (GD) 9.5 before hippocampal neurons were isolated and cultured from embryonic mice for further analysis. Interestingly, strongest effects were observed when the perineuronal net (PNN) wearing subpopulation of neurons was analysed. Here, a significant reduction of aggrecan staining intensity, area and soma size could be detected. Alterations of PNNs are often linked to neuropsychiatric diseases, changes in synaptic plasticity and in electrophysiology. Utilizing multielectrode array analysis (MEA), we observed a remarkable increase of the spontaneous network activity in neuronal networks after 21 days in vitro (DIV) when mother mice suffered a prenatal immune challenge. As PNNs are associated with GABAergic interneurons, our data indicate that this neuronal subtype might be stronger affected by a prenatal MIA. Degradation or damage of this subtype might cause the hyperexcitability observed in the whole network. In addition, embryonic neurons of the Poly I:C condition developed significantly shorter axons after five days in culture, while dendritic parameters and apoptosis rate remained unchanged. Structural analysis of synapse numbers revealed an increase of postsynaptic density 95 (PSD-95) puncta after 14 DIV and an increase of presynaptic vesicular glutamate transporter (vGlut) puncta after 21 DIV, while inhibitory synaptic proteins were not altered.

Gut-Brain Axis in the Early Postnatal Years of Life: A Developmental Perspective

Emerging evidence suggests that alterations in the development of the gastrointestinal (GI) tract during the early postnatal period can influence brain development and vice-versa. It is increasingly recognized that communication between the GI tract and brain is mainly driven by neural, endocrine, immune, and metabolic mediators, collectively called the gut-brain axis (GBA). Changes in the GBA mediators occur in response to the developmental changes in the body during this period. This review provides an overview of major developmental events in the GI tract and brain in the early postnatal period and their parallel developmental trajectories under physiological conditions. Current knowledge of GBA mediators in context to brain function and behavioral outcomes and their synthesis and metabolism (site, timing, etc.) is discussed. This review also presents hypotheses on the role of the GBA mediators in response to the parallel development of the GI tract and brain in infants.

Two distinct neuroanatomical subtypes of schizophrenia revealed using machine learning

Neurobiological heterogeneity in schizophrenia is poorly understood and confounds current analyses. We investigated neuroanatomical subtypes in a multi-institutional multi-ethnic cohort, using novel semi-supervised machine learning methods designed to discover patterns associated with disease rather than normal anatomical variation. Structural MRI and clinical measures in established schizophrenia (n = 307) and healthy controls (n = 364) were analysed across three sites of PHENOM (Psychosis Heterogeneity Evaluated via Dimensional Neuroimaging) consortium. Regional volumetric measures of grey matter, white matter, and CSF were used to identify distinct and reproducible neuroanatomical subtypes of schizophrenia. Two distinct neuroanatomical subtypes were found. Subtype 1 showed widespread lower grey matter volumes, most prominent in thalamus, nucleus accumbens, medial temporal, medial prefrontal/frontal and insular cortices. Subtype 2 showed increased volume in the basal ganglia and internal capsule, and otherwise normal brain volumes. Grey matter volume correlated negatively with illness duration in Subtype 1 (r = -0.201, P = 0.016) but not in Subtype 2 (r = -0.045, P = 0.652), potentially indicating different underlying neuropathological processes. The subtypes did not differ in age (t = -1.603, df = 305, P = 0.109), sex (chi-square = 0.013, df = 1, P = 0.910), illness duration (t = -0.167, df = 277, P = 0.868), antipsychotic dose (t = -0.439, df = 210, P = 0.521), age of illness onset (t = -1.355, df = 277, P = 0.177), positive symptoms (t = 0.249, df = 289, P = 0.803), negative symptoms (t = 0.151, df = 289, P = 0.879), or antipsychotic type (chi-square = 6.670, df = 3, P = 0.083). Subtype 1 had lower educational attainment than Subtype 2 (chi-square = 6.389, df = 2, P = 0.041). In conclusion, we discovered two distinct and highly reproducible neuroanatomical subtypes. Subtype 1 displayed widespread volume reduction correlating with illness duration, and worse premorbid functioning. Subtype 2 had normal and stable anatomy, except for larger basal ganglia and internal capsule, not explained by antipsychotic dose. These subtypes challenge the notion that brain volume loss is a general feature of schizophrenia and suggest differential aetiologies. They can facilitate strategies for clinical trial enrichment and stratification, and precision diagnostics.

Impact of Endocannabinoid System Manipulation on Neurodevelopmental Processes Relevant to Schizophrenia

The neurodevelopmental hypothesis of schizophrenia has received much support from epidemiological and neuropathological studies and provides a framework to explain how early developmental abnormalities might manifest as psychosis in early adulthood. According to this theory, the onset of schizophrenia is likely the result of a complex interplay between a genetic predisposition and environmental factors whose respective influence might contribute to the etiology and progression of the disorder. The two most sensitive windows for neurodevelopment are the prenatal/perinatal and the adolescent windows, both of which are characterized by specific processes impinging upon brain structure and functionality, whose alterations may contribute to the onset of schizophrenia. An increasing number of articles suggest the involvement of the endocannabinoid system in the modulation of at least some of these processes, especially in the prenatal/perinatal window. Thus, it is not surprising that disturbing the physiological role of endocannabinoid signaling in these sensitive windows might alter the correct formation of neuronal networks, eventually predisposing to neuropsychiatric diseases later in life. We review the most recent preclinical studies that evaluated the impact of endocannabinoid system modulation in the two sensitive developmental windows on neurodevelopmental processes that possess a specific relevance to schizophrenia.

Analysis of GWAS-Derived Schizophrenia Genes for Links to Ischemia-Hypoxia Response of the Brain

Obstetric complications (OCs) can induce major adverse conditions for early brain development and predispose to mental disorders, including schizophrenia (SCZ). We previously hypothesized that SCZ candidate genes respond to ischemia-hypoxia as part of OCs which impacts neurodevelopment. We here tested for an overlap between SCZ genes from genome-wide association study (GWAS) (n=458 genes from 145 loci of the most recent GWAS dataset in SCZ) and gene sets for ischemia-hypoxia response. Subsets of SCZ genes were related to (a) mutation-intolerant genes (LoF database), (b) role in monogenic disorders of the nervous system (OMIM, manual annotations), and (c) synaptic function (SynGO). Ischemia-hypoxia response genes of the brain (IHR genes, n=1,629), a gene set from RNAseq in focal brain ischemia (BH, n=2,449) and genes from HypoxiaDB (HDB, n=2,289) were overlapped with the subset of SCZ genes and tested for enrichment with Chi-square tests (p < 0.017). The SCZ GWAS dataset was enriched for LoF (n=112; p=0.0001), and the LoF subset was enriched for IHR genes (n=25; p=0.0002), BH genes (n=35; p=0.0001), and HDB genes (n=23; p=0.0005). N=96 genes of the SCZ GWAS dataset (21%) could be linked to a monogenic disorder of the nervous system whereby IHR genes (n=19, p=0.008) and BH genes (n=23; p=0.002) were found enriched. N=46 synaptic genes were found in the SCZ GWAS gene set (p=0.0095) whereby enrichments for IHR genes (n=20; p=0.0001) and BH genes (n=13; p=0.0064) were found. In parallel, detailed annotations of SCZ genes for a role of the hypoxia-inducible factors (HIFs) identified n=33 genes of high interest. Genes from SCZ GWAS were enriched for mutation-intolerant genes which in turn were strongly enriched for three sets of genes for the ischemia-hypoxia response that may be invoked by OCs. A subset of one fifth of SCZ genes has established roles in monogenic disorders of the nervous system which was enriched for two gene sets related to ischemia-hypoxia. SCZ genes related to synaptic functions were also related to ischemia-hypoxia. Variants of SCZ genes interacting with ischemia-hypoxia provide a specific starting point for functional and genomic studies related to OCs.

Interaction between TNF-α and oxidative stress status in first-episode drug-naïve schizophrenia

There has been evidence that the disturbances of TNF-α and the oxidative stress (OxS) status are involved in the mechanism of schizophrenia. However, the results of their levels in schizophrenia are still controversial, and their interactions have not yet been examined, especially in first-episode drug-naïve (FEDN) patients. We therefore applied Enzyme-linked immunosorbent assays (ELISAs) method to compare peripheral blood serum TNF-α, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde (MDA) levels in 119 FEDN patients with schizophrenia and 135 healthy controls. We found that TNF-α and MDA were higher, whereas GSH-Px was lower, in FEDN patients with schizophrenia compared to healthy controls (TNF-α, 2.21 ± 0.33 vs. 2.11 ± 0.36, Bonferroni p = 0.04; MDA, 2.95 ± 0.87 vs. 2.68 ± 0.76, Bonferroni p = 0.04, GSH-Px, 177.33 ± 28.84 vs. 188.32 ± 29.34, Bonferroni p = 0.03). Furthermore, TNF-α levels had an independent positive association with negative symptoms (r = 0.37, Bonferroni p < 0.001). Finally, GSH-Px levels were negatively associated with the presence of schizophrenia (B =-0.014, Wald statistic = 9.22, p = 0.002, 95 %CI = 0.97-0.99), while the interaction of TNF-α with MDA was a risk factor for schizophrenia (B = 0.22, Wald statistic = 10.06, p = 0.002, 95 %CI = 1.09-1.43). Our results suggest that TNF-α and disturbance of oxidative stress status as well as their interaction may be involved in the pathophysiology of schizophrenia.

Cytokine concentrations throughout pregnancy and risk for psychosis in adult offspring: a longitudinal case-control study

BACKGROUND

Schizophrenia has been associated with pregnancy and birth complications and fetal exposure to inflammation is thought to be a common underlying mechanism. However, whether the risk is specific to particular phases of pregnancy is unclear. The aim of this study was to characterise and compare longitudinal patterns of maternal serum concentrations of cytokines across pregnancy between offspring who were later ascertained to have a psychotic disorder, non-psychotic siblings of these cases, and unrelated, non-psychotic individuals who served as controls.

METHODS

The National Collaborative Perinatal Project was a large-scale prospective longitudinal study that assessed the effects of perinatal factors on infant and child development. At sites across the USA, over 50 000 pregnant women were enrolled during prenatal clinical visits between 1959 and 1965. The present study draws from the Philadelphia cohort, which includes 9236 surviving offspring of 6753 pregnant women. Psychotic disorder diagnoses in adulthood were assessed with review of medical records and were confirmed with a validation study. Concentrations of TNFα, IL-1β, IL-5, IL-6, IL-8, IL-10, and IL-17a were assessed using a multiplex bead assay in archived maternal serum samples collected across prenatal visits and birth. We characterized cytokine patterns with linear mixed models.

FINDINGS

Our final sample comprised 90 cases, 79 siblings (of 40 cases), and 273 matched controls. Concentrations of proinflammatory cytokines TNFα, IL-1β, and IL-6 were significantly higher in maternal serum of offspring who later developed psychosis compared with maternal serum of matched controls. These differences were greatest in the first half of pregnancy (7-20 weeks), with no difference observed during the second half of pregnancy.

INTERPRETATION

Our results suggest that exposure to high maternal proinflammatory cytokine concentrations in early pregnancy might play a part in psychosis. These findings place the timing of risk associated with maternal inflammation much earlier in prenatal development than previously documented in humans and provide insight into a potential developmental pathway to the disorder.

FUNDING

National Institute of Mental Health (P50) Silvio O Conte Center at Johns Hopkins, Stanley Foundation, March of Dimes, Yale University, National Science Foundation, and National Institute of Child Health and Human Development/Division of Intramural Population Health Research.

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