Prenatal Maternal Stress and the Cascade of Risk to Schizophrenia Spectrum Disorders in Offspring

Prenatal maternal Inflammation, childhood cognition and adolescent depressive symptoms

BACKGROUND

Accumulating evidence indicates that higher prenatal maternal inflammation is associated with increased depression risk in adolescent and adult-aged offspring. Prenatal maternal inflammation (PNMI) may increase the likelihood for offspring to have lower cognitive performance, which, in turn, may heighten risk for depression onset. Therefore, this study explored the potential mediating role of childhood cognitive performance in the relationship between PNMI and adolescent depressive symptoms in offspring.

METHODS

Participants included 696 mother-offspring dyads from the Child Health and Development Studies (CHDS) cohort. Biomarkers of maternal inflammation [interleukin (IL)-6, IL-8, IL-1 receptor antagonist (IL-1RA) and soluble TNF receptor-II (sTNF-RII)] were assayed from first (T1) and second trimester (T2) sera. Childhood (ages 9-11) cognitive performance was assessed via standardized Peabody Picture Vocabulary Test (PPVT), a measure of receptive vocabulary correlated with general intelligence. Adolescent (ages 15-17) depressive symptoms were assessed via self-report.

RESULTS

There were no significant associations between T1 biomarkers and childhood PPVT or adolescent depressive symptoms. Higher T2 IL1-RA was directly associated with lower childhood PPVT (b = -0.21, SE = 0.08, t = -2.55, p = 0.01), but not with adolescent depressive symptoms. T2 IL-6 was not directly associated with childhood PPVT, but higher T2 IL-6 was directly associated at borderline significance with greater depressive symptoms in adolescence (b = 0.05, SE = 0.03, t = 1.96, p = 0.05). Lower childhood PPVT predicted significantly higher adolescent depressive symptoms (b = -0.07, SE = 0.02, t = -2.99, p < 0.01). There was a significant indirect effect of T2 IL-1RA on adolescent depressive symptoms via childhood PPVT (b = 0.03, 95 % CI = 0.002-0.03) indicating a partially mediated effect. No significant associations were found with T2 sTNF-RII nor IL-8.

CONCLUSIONS

Lower childhood cognitive performance, such as that indicated by a lower PPVT score, represents a potential mechanism through which prenatal maternal inflammation contributes to adolescent depression risk in offspring.

Exploring causal mechanisms of psychosis risk

Robust epidemiological evidence of risk and protective factors for psychosis is essential to inform preventive interventions. Previous evidence syntheses have classified these risk and protective factors according to their strength of association with psychosis. In this critical review we appraise the distinct and overlapping mechanisms of 25 key environmental risk factors for psychosis, and link these to mechanistic pathways that may contribute to neurochemical alterations hypothesised to underlie psychotic symptoms. We then discuss the implications of our findings for future research, specifically considering interactions between factors, exploring universal and subgroup-specific factors, improving understanding of temporality and risk dynamics, standardising operationalisation and measurement of risk and protective factors, and developing preventive interventions targeting risk and protective factors.

The cliff edge model of the evolution of schizophrenia: Mathematical, epidemiological, and genetic evidence

How has schizophrenia, a condition that significantly reduces an individual's evolutionary fitness, remained common across generations and cultures? Numerous theories about the evolution of schizophrenia have been proposed, most of which are not consistent with modern epidemiological and genetic evidence. Here, we briefly review this evidence and explore the cliff edge model of schizophrenia. It suggests that schizophrenia is the extreme manifestation of a polygenic trait or a combination of traits that, within a normal range of variation, confer cognitive, linguistic, and/or social advantages. Only beyond a certain threshold, these traits precipitate the onset of schizophrenia and reduce fitness. We provide the first mathematical model of this qualitative concept and show that it requires only very weak positive selection of the underlying trait(s) to explain today's schizophrenia prevalence. This prediction, along with expectations about the effect size of schizophrenia risk alleles, are surprisingly well matched by empirical evidence. The cliff edge model predicts a dynamic change of selection of risk alleles, which explains the contradictory findings of evolutionary genetic studies.

Sex-Specific Pathways From Prenatal Maternal Inflammation to Adolescent Depressive Symptoms

Importance

Prenatal maternal inflammation has been associated with major depressive disorder in offspring in adulthood as well as with internalizing and externalizing symptoms in childhood; however, the association between prenatal inflammation and offspring depression in adolescence has yet to be examined.

Objective

To determine whether maternal levels of inflammatory biomarkers during pregnancy are associated with depressive symptomatology in adolescent-aged offspring and to examine how gestational timing, offspring sex, and childhood psychiatric symptoms impact these associations.

Design, Setting, and Participants

This was an observational study of a population-based birth cohort from the Child Health and Development Studies (CHDS), which recruited almost all mothers receiving obstetric care from the Kaiser Foundation Health Plan (KFHP) in Alameda County, California, between June 1959 and September 1966. Pregnancy data and blood sera were collected from mothers, and offspring psychiatric symptom data were collected in childhood (ages 9-11 years) and adolescence (ages 15-17 years). Mother-offspring dyads with available maternal prenatal inflammatory biomarkers during first and/or second trimesters and offspring depressive symptom data at adolescent follow-up were included. Data analyses took place between March 2020 and June 2023.

Exposures

Levels of inflammatory biomarkers (interleukin 6 [IL-6], IL-8, IL-1 receptor antagonist [IL-1RA], and soluble tumor necrosis factor receptor-II) assayed from maternal sera in the first and second trimesters of pregnancy.

Main Outcomes and Measures

Self-reported depressive symptoms at adolescent follow-up.

Results

A total of 674 mothers (mean [SD] age, 28.1 [5.9] years) and their offspring (350 male and 325 female) were included in this study. Higher second trimester IL-6 was significantly associated with greater depressive symptoms in offspring during adolescence (b, 0.57; SE, 0.26); P = .03). Moderated mediation analyses showed that childhood externalizing symptoms significantly mediated the association between first trimester IL-6 and adolescent depressive symptoms in male offspring (b, 0.18; 95% CI, 0.02-0.47), while childhood internalizing symptoms mediated the association between second trimester IL-1RA and adolescent depressive symptoms in female offspring (b, 0.80; 95% CI, 0.19-1.75).

Conclusions and Relevance

In this study, prenatal maternal inflammation was associated with depressive symptoms in adolescent-aged offspring. The findings of the study suggest that pathways to adolescent depressive symptomatology from prenatal risk factors may differ based on both the timing of exposure to prenatal inflammation and offspring sex.

The social determinants of mental health and disorder: evidence, prevention and recommendations

People exposed to more unfavourable social circumstances are more vulnerable to poor mental health over their life course, in ways that are often determined by structural factors which generate and perpetuate intergenerational cycles of disadvantage and poor health. Addressing these challenges is an imperative matter of social justice. In this paper we provide a roadmap to address the social determinants that cause mental ill health. Relying as far as possible on high-quality evidence, we first map out the literature that supports a causal link between social determinants and later mental health outcomes. Given the breadth of this topic, we focus on the most pervasive social determinants across the life course, and those that are common across major mental disorders. We draw primarily on the available evidence from the Global North, acknowledging that other global contexts will face both similar and unique sets of social determinants that will require equitable attention. Much of our evidence focuses on mental health in groups who are marginalized, and thus often exposed to a multitude of intersecting social risk factors. These groups include refugees, asylum seekers and displaced persons, as well as ethnoracial minoritized groups; lesbian, gay, bisexual, transgender and queer (LGBTQ+) groups; and those living in poverty. We then introduce a preventive framework for conceptualizing the link between social determinants and mental health and disorder, which can guide much needed primary prevention strategies capable of reducing inequalities and improving population mental health. Following this, we provide a review of the evidence concerning candidate preventive strategies to intervene on social determinants of mental health. These interventions fall broadly within the scope of universal, selected and indicated primary prevention strategies, but we also briefly review important secondary and tertiary strategies to promote recovery in those with existing mental disorders. Finally, we provide seven key recommendations, framed around social justice, which constitute a roadmap for action in research, policy and public health. Adoption of these recommendations would provide an opportunity to advance efforts to intervene on modifiable social determinants that affect population mental health.

Motion and Form Perception in Childhood-Onset Schizophrenia

(1) Background: Childhood-onset schizophrenia (COS) is a rare type of psychotic disorder characterized by delusions, hallucinations, grossly disorganized behavior, and poor psychosocial functioning. The etiology of COS is unknown, but neurodevelopmental factors are likely to play a critical role. A potential neurodevelopmental anomaly marker is the dorsal visual system dysfunction, which is implicated in motion perception, spatial functions, and attention. (2) Methods: To elucidate the role of the dorsal visual system in COS, we investigated 21 patients with COS and 21 control participants matched for age, sex, education, IQ, and parental socioeconomic status. Participants completed a motion and form coherence task, during which one assesses an individual's ability to detect the direction of motion within a field of moving elements or dots and to recognize a meaningful form or object from a set of fragmented or disconnected visual elements, respectively. (3) Results: The patients with COS were impaired in both visual tasks compared to the control participants, but the evidence for the deficit was more substantial for motion perception than for form perception (form: BF10 = 27.22; motion: BF10 = 6.97 × 106). (4) Conclusions: These results highlight the importance of dorsal visual stream vulnerability in COS, a potential marker of neurodevelopmental anomalies.

Bdnf-Nrf-2 crosstalk and emotional behavior are disrupted in a sex-dependent fashion in adolescent mice exposed to maternal stress or maternal obesity

Maternal obesity has been recognized as a stressor affecting the developing fetal brain, leading to long-term negative outcomes comparable to those resulting from maternal psychological stress, although the mechanisms have not been completely elucidated. In this study, we tested the hypothesis that adverse prenatal conditions as diverse as maternal stress and maternal obesity might affect emotional regulation and stress response in the offspring through common pathways, with a main focus on oxidative stress and neuroplasticity. We contrasted and compared adolescent male and female offspring in two mouse models of maternal psychophysical stress (restraint during pregnancy - PNS) and maternal obesity (high-fat diet before and during gestation - mHFD) by combining behavioral assays, evaluation of the hypothalamic-pituitary-adrenal (HPA) axis reactivity, immunohistochemistry and gene expression analysis of selected markers of neuronal function and neuroinflammation in the hippocampus, a key region involved in stress appraisal. Prenatal administration of the antioxidant N-acetyl-cysteine (NAC) was used as a strategy to protect fetal neurodevelopment from the negative effects of PNS and mHFD. Our findings show that these two stressors produce overlapping effects, reducing brain anti-oxidant defenses (Nrf-2) and leading to sex-dependent impairments of hippocampal Bdnf expression and alterations of the emotional behavior and HPA axis functionality. Prenatal NAC administration, by restoring the redox balance, was able to exert long-term protective effects on brain development, suggesting that the modulation of redox pathways might be an effective strategy to target common shared mechanisms between different adverse prenatal conditions.

Effects of Prenatal Stress on Behavior, Cognition, and Psychopathology: A Comprehensive Review

Prenatal stress is increasingly recognized as a significant factor impacting an individual's life from the beginning. This comprehensive review explores the intricate relationship between prenatal stress and its effects on behaviour, cognition, and psychopathology. Key findings reveal that prenatal stress can lead to a wide range of adverse outcomes in offspring, including neurodevelopmental disorders, emotional dysregulation, cognitive deficits, mood disorders, and an increased risk of psychopathological conditions. These effects' mechanisms involve epigenetic modifications, hypothalamic-pituitary-adrenal (HPA) axis dysregulation, neurodevelopmental alterations, inflammatory processes, and changes in brain structure and function. Moreover, moderating factors such as maternal stress levels, maternal mental health, socioeconomic status, social support, and early-life adversity can significantly influence the impact of prenatal stress. The review also discusses intervention and prevention strategies, emphasizing the importance of prenatal stress reduction programs, maternal mental health support, nutritional interventions, and targeted early interventions for at-risk populations. These findings have substantial implications for public health and clinical practice, highlighting the need for a holistic approach to prenatal care that prioritizes maternal well-being and mitigates the lasting effects of prenatal stress. Addressing this critical issue promises healthier generations and stronger communities in the future.

The long-lasting effects of aceclofenac, a COX-2 inhibitor, in a Poly I:C-Induced maternal immune activation model of schizophrenia in rats

It is well established that rats exposed to inflammation during pregnancy or the perinatal period have an increased chance of developing schizophrenia-like symptoms and behaviors, and people with schizophrenia also have raised levels of inflammatory markers. Therefore, there is evidence supporting the idea that anti-inflammatory drugs may have therapeutic benefits. Aceclofenac is a nonsteroidal anti-inflammatory drug that has anti-inflammatory properties and is used clinically to treat inflammatory and painful processes such as osteoarthritis and rheumatoid arthritis, making it a potential candidate for preventive or adjunctive therapy in schizophrenia. This study therefore examined the effect of aceclofenac in a maternal immune activation model of schizophrenia, in which polyinosinic-polycytidylic acid (Poly I:C) (8 mg/kg, i.p.) was administered to pregnant rat dams. Young female rat pups received daily aceclofenac (5, 10, and 20 mg/kg, i.p., n = 10) between postnatal day 56 and 76. The effects of aceclofenac were compared with assessment of behavioral tests and ELISA results. During the postnatal days (PNDs) 73-76, behavioral tests were conducted in rats, and on PND 76, ELISA tests were performed to examine the changes in Tumor necrosis factor alpha (TNF-α), Interleukin-1β (IL-1β), Brain-derived neurotrophic factor (BDNF), and nestin levels. Aceclofenac treatment reversed deficits in prepulse inhibition, novel object recognition, social interaction, and locomotor activity tests. In addition, aceclofenac administration decreased TNF-α and IL-1β expression in the prefrontal cortex and hippocampus. In contrast, BDNF and nestin levels did not change significantly during treatment with aceclofenac. Taken together, these results suggest that aceclofenac may be an alternative therapeutic adjunctive strategy to improve the clinical expression of schizophrenia in the further studies.

Sex and age differences in social and cognitive function in offspring exposed to late gestational hypoxia

Background

Gestational sleep apnea affects 8-26% of pregnancies and can increase the risk for autism spectrum disorder (ASD) in offspring. ASD is a neurodevelopmental disorder associated with social dysfunction, repetitive behaviors, anxiety, and cognitive impairment. To examine the relationship between gestational sleep apnea and ASD-associated behaviors, we used a chronic intermittent hypoxia (CIH) protocol between gestational days (GD) 15-19 in pregnant rats to model late gestational sleep apnea. We hypothesized that late gestational CIH would produce sex- and age-specific social, mood, and cognitive impairments in offspring.

Methods

Timed pregnant Long-Evans rats were exposed to CIH or room air normoxia from GD 15-19. Behavioral testing of offspring occurred during either puberty or young adulthood. To examine ASD-associated phenotypes, we quantified ASD-associated behaviors (social function, repetitive behaviors, anxiety-like behaviors, and spatial memory and learning), hippocampal activity (glutamatergic NMDA receptors, dopamine transporter, monoamine oxidase-A, EGR-1, and doublecortin), and circulating hormones in offspring.

Results

Late gestational CIH induced sex- and age-specific differences in social, repetitive and memory functions in offspring. These effects were mostly transient and present during puberty. In female pubertal offspring, CIH impaired social function, increased repetitive behaviors, and increased circulating corticosterone levels, but did not impact memory. In contrast, CIH transiently induced spatial memory dysfunction in pubertal male offspring but did not impact social or repetitive functions. Long-term effects of gestational CIH were only observed in female offspring, wherein CIH induced social disengagement and suppression of circulating corticosterone levels in young adulthood. No effects of gestational CIH were observed on anxiety-like behaviors, hippocampal activity, circulating testosterone levels, or circulating estradiol levels, regardless of sex or age of offspring.

Conclusions

Our results indicate that hypoxia-associated pregnancy complications during late gestation can increase the risk for ASD-associated behavioral and physiological outcomes, such as pubertal social dysfunction, corticosterone dysregulation, and memory impairments.

Urinary 1H NMR Metabolomic Analysis of Prenatal Maternal Stress Due to a Natural Disaster Reveals Metabolic Risk Factors for Non-Communicable Diseases: The QF2011 Queensland Flood Study

Prenatal stress alters fetal programming, potentially predisposing the ensuing offspring to long-term adverse health outcomes. To gain insight into environmental influences on fetal development, this QF2011 study evaluated the urinary metabolomes of 4-year-old children (n = 89) who were exposed to the 2011 Queensland flood in utero. Proton nuclear magnetic resonance spectroscopy was used to analyze urinary metabolic fingerprints based on maternal levels of objective hardship and subjective distress resulting from the natural disaster. In both males and females, differences were observed between high and low levels of maternal objective hardship and maternal subjective distress groups. Greater prenatal stress exposure was associated with alterations in metabolites associated with protein synthesis, energy metabolism, and carbohydrate metabolism. These alterations suggest profound changes in oxidative and antioxidative pathways that may indicate a higher risk for chronic non-communicable diseases such obesity, insulin resistance, and diabetes, as well as mental illnesses, including depression and schizophrenia. Thus, prenatal stress-associated metabolic biomarkers may provide early predictors of lifetime health trajectories, and potentially serve as prognostic markers for therapeutic strategies in mitigating adverse health outcomes.

Prospective associations between various prenatal exposures to maternal psychological stress and neurodevelopment in children within 24 months after birth

BACKGROUND

There is increasing evidence that prenatal exposure to maternal psychological distress may be a factor influencing offspring neurodevelopment, but stress type-dependent effects of maternal psychological distress on offspring neurodevelopment in early childhood have yet to be fully elucidated. Additionally, although positive maternal mental health exerts potential effects in protecting against adverse health outcomes, few investigators have considered the effects of positive maternal mental health on offspring neurodevelopment in early childhood.

AIMS

To determine the associations between various prenatal exposures to maternal psychological distress and positive life-event experiences and offspring neurodevelopment within 24 months of age.

METHODS

A total of 4412 mother-child dyads were recruited from the Shanghai Maternal-Child Pairs Cohort (Shanghai MCPC). Maternal perceived stress, negative life-event stress, positive life-event experiences around the time of conception (i.e., three months prior to and after conception) were assessed at 12-16 gestational weeks, and maternal anxiety and depressive symptoms were assessed at 32-36 gestational weeks. We measured children's neurodevelopment using the Ages and Stages Questionnaire, Third Edition (ASQ-3) at two, six, 12, and 24 months postnatally. We then exploited generalized linear models to estimate the associations between prenatal maternal psychological distress and positive life-event experiences and children's neurodevelopment at the above periods, and generalized linear mixed models were applied to assess the associations between maternal psychological distress and positive life-event experiences and suspected developmental delay (SDD) in children within 24 months after birth based on a longitudinal design.

RESULTS

Maternal perceived stress and negative life-event stress around the time of conception, and anxiety and depressive symptoms during late pregnancy were negatively associated with scores of children's neurodevelopment at two, six, 12, and 24 months of age; while maternal life-event experiences were positively associated with scores of children's neurodevelopment. Longitudinal analysis revealed that higher levels of maternal negative life-event stress and depressive symptoms augmented the risk of SDD in personal-social (OR = 1.435, 1.681). Mothers who experienced higher levels of positive life-event experiences exhibited a reduced risk of SDD in gross motor and personal-social domains (OR = 0.373, 0.350).

CONCLUSIONS

Prenatal exposure to maternal psychological distress is negatively associated with children's neurodevelopment in early childhood depending upon the type of distress. Maternal positive life-event experiences around the time of conception appeared to present potential benefits for child neurodevelopment.

A systematic review and narrative synthesis of fathers' (including migrant fathers') experiences of pregnancy and childbirth

OBJECTIVE

The purpose of this review was to consider factors that influence the experiences of pregnancy and childbirth by fathers including migrant fathers.

METHOD

A systematic review and narrative synthesis were conducted as per the PRISMA guidelines. The spider tool was used to build a search strategy which was used to conduct literature search in eight identified electronic databases: ASSIA, CINAHL, EMBASE, MEDLINE, PsycINFO, PUBMED, Sage and Scopus. Grey literature was searched through the King's Fund Library database, Ethos, The North Grey Literature Collection, Social Care Online and other charity websites such as the Refugee Council and Joseph Rowntree Foundation. The search was conducted across all the databases in the week commencing January 7, 2019, and restricted to studies published in the English language.

RESULTS

The search across all the eight electronic databases identified 2564 records, 13 records through grey literature databases/websites and an additional 23 records identified through hand-searching/forward citation. The number of records after duplicates were removed was 2229. Record screening based on titles and abstracts identified 69 records for full text screening. Dual screening of these full text records identified 12 full records from 12 separate studies, eight of which were qualitative studies, three of which were quantitative studies and one mixed method study.

FINDINGS

This review has revealed three main themes: influence of society and health professionals; adjustment to a new life of fatherhood; and involvement in maternity care. However, the literature has focused on non-migrant father's experiences of pregnancy and childbirth, with little attention paid to fathers who may be migrants.

KEY CONCLUSION AND IMPLICATIONS FOR PRACTICE

This review has exposed a dearth of research on migrant fathers' experiences of pregnancy and childbirth in an era of increasing globalisation and migration between countries. Midwives and other health professionals should be alert to the needs of any father when providing maternity care. More research is needed which considers experiences of migrants and how choosing to move to a new country or being forced to move could influence migrant father's experiences and therefore their needs.

Environmental Risk Factors and Cognitive Outcomes in Psychosis: Pre-, Perinatal, and Early Life Adversity

Risk for psychosis begins to accumulate as early as the fetal period through exposure to obstetric complications like fetal hypoxia, maternal stress, and prenatal infection. Stressors in the postnatal period, such as childhood trauma, peer victimization, and neighborhood-level adversity, further increase susceptibility for psychosis. Cognitive difficulties are among the first symptoms to emerge in individuals who go on to develop a psychotic disorder. We review the relationship between pre-, perinatal, and early childhood adversities and cognitive outcomes in individuals with psychosis. Current evidence shows that the aforementioned environmental risk factors may be linked to lower overall intelligence and executive dysfunction, beginning in the premorbid period and persisting into adulthood in individuals with psychosis. It is likely that early life stress contributes to cognitive difficulties in psychosis through dysregulation of the body's response to stress, causing changes such as increased cortisol levels and chronic immune activation, which can negatively impact neurodevelopment. Intersectional aspects of identity (e.g., sex/gender, race/ethnicity), as well as gene-environment interactions, likely inform the developmental cascade to cognitive difficulties throughout the course of psychotic disorders and are reviewed below. Prospective studies of birth cohorts will serve to further clarify the relationship between early-life environmental risk factors and cognitive outcomes in the developmental course of psychotic disorders. Specific methodological recommendations are provided for future research.

Psychological legacies of intergenerational trauma under South African apartheid: Prenatal stress predicts greater vulnerability to the psychological impacts of future stress exposure during late adolescence and early adulthood in Soweto, South Africa

BACKGROUND

South Africa's rates of psychiatric morbidity are among the highest in sub-Saharan Africa and are foregrounded by the country's long history of political violence during apartheid. Growing evidence suggests that in utero stress exposure is a potent developmental risk factor for future mental illness risk, yet the extent to which the psychiatric effects of prenatal stress impact the next generation are unknown. We evaluate the intergenerational effects of prenatal stress experienced during apartheid on psychiatric morbidity among children at ages 17-18 and also assess the moderating effects of maternal age, social support, and past household adversity.

METHODS

Participants come from Birth-to-Twenty, a longitudinal birth cohort study in Soweto-Johannesburg, South Africa's largest peri-urban township which was the epicentre of violent repression and resistance during the final years of the apartheid regime. Pregnant women were prospectively enrolled in 1990 and completed questionnaires assessing social experiences, and their children's psychiatric morbidity were assessed at ages 17-18.

RESULTS

Full data were available from 304 mother-child pairs in 2007-8. Maternal prenatal stress in 1990 was not directly associated greater psychiatric morbidity during at ages 17-18. Maternal age and past household adversity moderated the intergenerational mental health effects of prenatal stress such that children born to younger mothers and late adolescent/young adult children experiencing greater household adversity exhibited worse psychiatric morbidity at ages 17-18. Social support did not buffer against the long-term psychiatric impacts of prenatal stress.

CONCLUSIONS

Greater prenatal stress from apartheid predicted adverse psychiatric outcomes among children born to younger mothers and adolescents/young adults who experienced greater concurrent stress. Our findings suggest that prenatal stress may affect adolescent mental health, have stress-sensitising effects, and represent possible intergenerational effects of trauma experienced under apartheid in this sample.

The Potential Role of PPARs in the Fetal Origins of Adult Disease

The fetal origins of adult disease (FOAD) hypothesis holds that events during early development have a profound impact on one’s risk for the development of future adult disease. Studies from humans and animals have demonstrated that many diseases can begin in childhood and are caused by a variety of early life traumas, including maternal malnutrition, maternal disease conditions, lifestyle changes, exposure to toxins/chemicals, improper medication during pregnancy, and so on. Recently, the roles of Peroxisome proliferator-activated receptors (PPARs) in FOAD have been increasingly appreciated due to their wide variety of biological actions. PPARs are members of the nuclear hormone receptor subfamily, consisting of three distinct subtypes: PPARα, β/δ, and γ, highly expressed in the reproductive tissues. By controlling the maturation of the oocyte, ovulation, implantation of the embryo, development of the placenta, and male fertility, the PPARs play a crucial role in the transition from embryo to fetus in developing mammals. Exposure to adverse events in early life exerts a profound influence on the methylation pattern of PPARs in offspring organs, which can affect development and health throughout the life course, and even across generations. In this review, we summarize the latest research on PPARs in the area of FOAD, highlight the important role of PPARs in FOAD, and provide a potential strategy for early prevention of FOAD.

Cultural evolution: The third component of mental illness heritability

Uchiyama et al. provide a theoretical framework to explain the gap between reported gene-environment interactions and real-life epidemiological statistics. Through cultural evolution, informed behavioral approaches mitigate the impact of environmental risk on disease onset. Similarly, here we propose that fostering certain behavioral traits, transmitted culturally or through access to scientific knowledge, could confer resilience to mental illnesses such as schizophrenia.

Prenatal chronic stress impairs the learning and memory ability via inhibition of the NO/cGMP/PKG pathway in the Hippocampus of offspring

Numerous clinical and animal studies have found that antenatal chronic stress can lead to pathological changes the hippocampal development from embryos to adult, but the mechanisms are not well understood. Proteomic analyses provide a new insight to explore the potential mechanisms of this impairment. In this study, gestating rats were subjected to chronic unpredictable mild stress (CUMS) during pregnant days using nine different stimulations, and the changes of the learning and memory performance and the expression of proteins in the hippocampus of offspring were measured. It was found that prenatal chronic stress led to growth retardation, impaired spatial learning and memory ability in the offspring. Furthermore, prenatal stress caused various degrees of damage to neurons, Nissl body, mitochondria and synaptic structures in hippocampal CA3 region of offspring. In addition, 26 significantly different expressed proteins (DEPs) were found between the two groups by using isoquantitative tag-based relative and absolute quantification (iTRAQ) proteomics analysis. Further analyses of these DEPs showed that involved with different molecular functions and several biological processes, such as biological regulation and metabolic processes. Among these, the KEGG pathway enrichment showed that learning and memory impairment was mainly associated with the cyclic guanosine monophosphate protein kinase G (cGMP-PKG) pathway. At the same time, compared with OPC group, the NO, nNOS and cGMP level were significantly decreased, and the expression of PKG protein was also dropped. All of these results suggested that pregnant rats exposed to chronic psychological stress might impair spatial learning and memory ability of offspring, by disturbing the NO/cGMP/PKG signaling pathway.

Infection and higher cortisol during pregnancy and risk for depressive symptoms in adolescent offspring

Prenatal infection, particularly at mid-gestation, has been associated with various psychopathological outcomes in offspring; however, findings linking prenatal infection to offspring depression outcomes have been mixed. Previous research indicates that it may be the co-occurrence of prenatal adversities (e.g., infection and stress) that are associated with depression outcomes in offspring. Nevertheless, no study to date has investigated whether higher levels of biomarkers linked to prenatal stress (e.g., cortisol) in the presence of infection may account for these outcomes. Participants were drawn from the Child Health and Development Studies (CHDS), a prospective, longitudinal study of pregnant women and their offspring. The present study included mother-offspring dyads from the Adolescent Study, a subsample of the CHDS cohort, whose offspring were assessed in adolescence and whose mothers also provided sera to be assayed for cortisol (n = 695). Hierarchical multivariable regressions were conducted to examine whether maternal cortisol during the first and second trimesters of pregnancy interacted with maternal infection to predict increased risk for symptoms of depression in adolescent offspring. There was a significant interaction of second trimester infection and higher cortisol on offspring depression scores during adolescence, controlling for maternal education (p = 0.04). Findings suggest that higher maternal cortisol may sensitize mothers and their offspring to the disruptive influences of infection during mid-pregnancy, conferring greater risk of depressive symptomatology in offspring.

Impact of stress on inhibitory neuronal circuits, our tribute to Bruce McEwen

This manuscript is dedicated to the memory of Bruce S. McEwen, to commemorate the impact he had on how we understand stress and neuronal plasticity, and the profound influence he exerted on our scientific careers. The focus of this review is the impact of stressors on inhibitory circuits, particularly those of the limbic system, but we also consider other regions affected by these adverse experiences. We revise the effects of acute and chronic stress during different stages of development and lifespan, taking into account the influence of the sex of the animals. We review first the influence of stress on the physiology of inhibitory neurons and on the expression of molecules related directly to GABAergic neurotransmission, and then focus on specific interneuron subpopulations, particularly on parvalbumin and somatostatin expressing cells. Then we analyze the effects of stress on molecules and structures related to the plasticity of inhibitory neurons: the polysialylated form of the neural cell adhesion molecule and perineuronal nets. Finally, we review the potential of antidepressants or environmental manipulations to revert the effects of stress on inhibitory circuits.

Prenatal earthquake stress exposure in different gestational trimesters is associated with methylation changes in the glucocorticoid receptor gene (NR3C1) and long-term working memory in adulthood

Prenatal stress exposure is thought to affect the long-term development of the foetal brain via the HPA axis and to change health outcomes in adulthood, including working memory (WM). The potential mechanism is that there is a critical period of brain development of the foetus, which is a result of selective adaptation to the external environment. The human glucocorticoid gene (NR3C1) is associated with memory and cognition. This study investigates the association between earthquake stress during pregnancy and CpG methylation of the NR3C1 exon 1_F promoter and its influence on working memory in adulthood. DNA methylation analysis using bisulfite sequencing PCR was quantified in 176 subjects who were exposed or not exposed to intrauterine earthquake and were divided into three groups based on the pregnancy trimester. The Hopkins Verbal Learning Test-Revised (HVLT-R) and Brief Visuospatial Memory Test-Revised (BVMT-R) were used to assess working memory performance. The methylated NR3C1 exon 1_F promoter of the prenatal earthquake exposure (PEE) group was significantly higher than that of the control group (CN). Analysis of subgroups indicated that the subjects in the second trimester of PEE group showed significantly higher methylation than those in the third trimester. Significantly low BVMT-R scores were detected in those who experienced prenatal earthquake in the second trimester of PEE group. Methylated CpG site 1 may play a critical role in contributing to lower BVMT-R scores in the second trimester in the PEE group, and may offer a potential epigenetic mechanism that links prenatal stress and long-term effects on working memory.

Neurobiological Highlights of Cognitive Impairment in Psychiatric Disorders

This review is focused on several psychiatric disorders in which cognitive impairment is a major component of the disease, influencing life quality. There are plenty of data proving that cognitive impairment accompanies and even underlies some psychiatric disorders. In addition, sources provide information on the biological background of cognitive problems associated with mental illness. This scientific review aims to summarize the current knowledge about neurobiological mechanisms of cognitive impairment in people with schizophrenia, depression, mild cognitive impairment and dementia (including Alzheimer's disease).The review provides data about the prevalence of cognitive impairment in people with mental illness and associated biological markers.

"SMALL BABY SYNDROME" AS A PREGNANCY-ASSOCITED GENERAL ADAPTATION SYNDROME (REVIEW)

OBJECTIVE

The aim: To analyze the current research literature devoted to the study of the mechanisms of the realization of stress factors during pregnancy.

PATIENTS AND METHODS

Materials and methods: The article presents an analysis and summarizes the literature devoted to the study of the mechanisms of the realization of stress factors during the pregnancy, the pathogenetic aspects of violations of the feto-placental complex, "critical periods of vulnerability", the long-term consequences of the transferred prenatal stress.

CONCLUSION

Conclusions: The paper summarizes that the condition of the mother and the feto-placental complex play an important role in many aspects of fetal development, that determine baby's physical and emotional health, personality formation in the future.

From Womb to Neighborhood: A Racial Analysis of Social Determinants of Psychosis in the United States

The authors examine U.S.-based evidence that connects characteristics of the social environment with outcomes across the psychosis continuum, from psychotic experiences to schizophrenia. The notion that inequitable social and economic systems of society significantly influence psychosis risk through proxies, such as racial minority and immigrant statuses, has been studied more extensively in European countries. While there are existing international reviews of social determinants of psychosis, none to the authors' knowledge focus on factors in the U.S. context specifically-an omission that leaves domestic treatment development and prevention efforts incomplete and underinformed. In this review, the authors first describe how a legacy of structural racism in the United States has shaped the social gradient, highlighting consequential racial inequities in environmental conditions. The authors offer a hypothesized model linking structural racism with psychosis risk through interwoven intermediary factors based on existing theoretical models and a review of the literature. Neighborhood factors, cumulative trauma and stress, and prenatal and perinatal complications were three key areas selected for review because they reflect social and environmental conditions that may affect psychosis risk through a common pathway shaped by structural racism. The authors describe evidence showing that Black and Latino people in the United States suffer disproportionately from risk factors within these three key areas, in large part as a result of racial discrimination and social disadvantage. This broad focus on individual and community factors is intended to provide a consolidated space to review this growing body of research and to guide continued inquiries into social determinants of psychosis in U.S. contexts.

A Characterization of the Effects of Minocycline Treatment During Adolescence on Structural, Metabolic, and Oxidative Stress Parameters in a Maternal Immune Stimulation Model of Neurodevelopmental Brain Disorders

BACKGROUND

Minocycline (MIN) is a tetracycline with antioxidant, anti-inflammatory, and neuroprotective properties. Given the likely involvement of inflammation and oxidative stress (IOS) in schizophrenia, MIN has been proposed as a potential adjuvant treatment in this pathology. We tested an early therapeutic window, during adolescence, as prevention of the schizophrenia-related deficits in the maternal immune stimulation (MIS) animal model.

METHODS

On gestational day 15, Poly I:C or vehicle was injected in pregnant Wistar rats. A total 93 male offspring received MIN (30 mg/kg) or saline from postnatal day (PND) 35-49. At PND70, rats were submitted to the prepulse inhibition test. FDG-PET and T2-weighted MRI brain studies were performed at adulthood. IOS markers were evaluated in frozen brain tissue.

RESULTS

MIN treatment did not prevent prepulse inhibition test behavioral deficits in MIS offspring. However, MIN prevented morphometric abnormalities in the third ventricle but not in the hippocampus. Additionally, MIN reduced brain metabolism in cerebellum and increased it in nucleus accumbens. Finally, MIN reduced the expression of iNOS (prefrontal cortex, caudate-putamen) and increased the levels of KEAP1 (prefrontal cortex), HO1 and NQO1 (amygdala, hippocampus), and HO1 (caudate-putamen).

CONCLUSIONS

MIN treatment during adolescence partially counteracts volumetric abnormalities and IOS deficits in the MIS model, likely via iNOS and Nrf2-ARE pathways, also increasing the expression of cytoprotective enzymes. However, MIN treatment during this peripubertal stage does not prevent sensorimotor gating deficits. Therefore, even though it does not prevent all the MIS-derived abnormalities evaluated, our results suggest the potential utility of early treatment with MIN in other schizophrenia domains.

Prenatal origins of neuropsychiatric diseases

AIM

The main objective is to review the available evidence in the literature for developmental origins of neuropsychiatric diseases and their underlying mechanisms. We also probe emerging cutting-edge prenatal MR imaging tools and their future role in advancing our understanding the prenatal footprints of neuropsychiatric disorders.

OBSERVATIONS

Both human and animal studies support early intrauterine origins of neuropsychiatric disease, particularly autism spectrum disorders (ASD), attention and hyperactivity disorders, schizophrenia, depression, anxiety and mood disorders. Specific mechanisms of intrauterine injury include infection, inflammation, hypoxia, hypoperfusion, ischaemia polysubstance use/abuse, maternal mental health and placental dysfunction.

CONCLUSIONS AND RELEVANCE

There is ample evidence to suggest developmental vulnerability of the foetal brain to intrauterine exposures that increases and individual's risk for neuropsychiatric disease, especially the risk of ASD, depression and anxiety. Elucidating the exact timing and mechanisms of injury can be difficult and require novel, non-invasive approaches to the study emerging structural and functional brain development of the foetus. Clinical care should both emphasise maternal health during pregnancy, as well as close, continued monitoring for at risk offspring throughout young adulthood for the early identification and treatment of neuropsychiatric diseases.

Shedding light on the role of CX3CR1 in the pathogenesis of schizophrenia

Schizophrenia has a complex and heterogeneous molecular and clinical picture. Over the years of research on this disease, many factors have been suggested to contribute to its pathogenesis. Recently, the inflammatory processes have gained particular interest in the context of schizophrenia due to the increasing evidence from epidemiological, clinical and experimental studies. Within the immunological component, special attention has been brought to chemokines and their receptors. Among them, CX3C chemokine receptor 1 (CX3CR1), which belongs to the family of seven-transmembrane G protein-coupled receptors, and its cognate ligand (CX3CL1) constitute a unique system in the central nervous system. In the view of regulation of the brain homeostasis through immune response, as well as control of microglia reactivity, the CX3CL1–CX3CR1 system may represent an attractive target for further research and schizophrenia treatment. In the review, we described the general characteristics of the CX3CL1–CX3CR1 axis and the involvement of this signaling pathway in the physiological processes whose disruptions are reported to participate in mechanisms underlying schizophrenia. Furthermore, based on the available clinical and experimental data, we presented a guide to understanding the implication of the CX3CL1–CX3CR1 dysfunctions in the course of schizophrenia.

An update on psychotic spectrum disorders and disasters

PURPOSE OF REVIEW

The aim of this study is to review the recent literature on disasters' impact on the course of psychotic spectrum disorders (PSDs) and how people with PSD fare during a disaster, including the effects of COVID-19.

RECENT FINDINGS

Several, but not all, studies examining disasters including earthquake-affected communities and refugee populations have found increased incidence of PSDs. Studies have been inconsistent regarding psychosis incidence in COVID-19 patients. Meanwhile, patients with PSD have been found to cope poorly in recent disasters including flooding and a nuclear accident. Patients with schizophrenia appear to be at particular risk during COVID-19 due to such issues as poor awareness of health precautions and the psychiatric impact of lockdown. However, novel methods including telepsychiatry have allowed care of this population to remain consistent during COVID-19.

SUMMARY

There is conflicting evidence as to the association between disasters and onset of PSD, and further study is needed to elucidate this link. Patients with PSDs are more likely to fare worse during disasters. Novel approaches to delivery of care have helped offset the psychiatric risks to PSD patients during the COVID-19 pandemic. These approaches may be applicable to other disaster scenarios or to general outpatient care.

SARS-CoV-2 Infection in Pregnant Women: Neuroimmune-Endocrine Changes at the Maternal-Fetal Interface

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has devastating effects on the population worldwide. Given this scenario, the extent of the impact of the disease on more vulnerable individuals, such as pregnant women, is of great concern. Although pregnancy may be a risk factor in respiratory virus infections, there are no considerable differences regarding COVID-19 severity observed between pregnant and nonpregnant women. In these circumstances, an emergent concern is the possibility of neurodevelopmental and neuropsychiatric harm for the offspring of infected mothers. Currently, there is no stronger evidence indicating vertical transmission of SARS-CoV-2; however, the exacerbated inflammatory response observed in the disease could lead to several impairments in the offspring's brain. Furthermore, in the face of historical knowledge on possible long-term consequences for the progeny's brain after infection by viruses, we must consider that this might be another deleterious facet of COVID-19. In light of neuroimmune interactions at the maternal-fetal interface, we review here the possible harmful outcomes to the offspring brains of mothers infected by SARS-CoV-2.

How do established developmental risk-factors for schizophrenia change the way the brain develops?

The recognition that schizophrenia is a disorder of neurodevelopment is widely accepted. The original hypothesis was coined more than 30 years ago and the wealth of supportive epidemiologically data continues to grow. A number of proposals have been put forward to suggest how adverse early exposures in utero alter the way the adult brain functions, eventually producing the symptoms of schizophrenia. This of course is extremely difficult to study in developing human brains, so the bulk of what we know comes from animal models of such exposures. In this review, I will summarise the more salient features of how the major epidemiologically validated exposures change the way the brain is formed leading to abnormal function in ways that are informative for schizophrenia symptomology. Surprisingly few studies have examined brain ontogeny from embryo to adult in such models. However, where there is longitudinal data, various convergent mechanisms are beginning to emerge involving stress and immune pathways. There is also a surprisingly consistent alteration in how very early dopamine neurons develop in these models. Understanding how disparate epidemiologically-validated exposures may produce similar developmental brain abnormalities may unlock convergent early disease-related pathways/processes.

Advancing Autism Research From Mice to Marmosets: Behavioral Development of Offspring Following Prenatal Maternal Immune Activation

Understanding the mechanism(s) by which maternal immune activation (MIA) during gestation may disrupt neurodevelopment and increase the susceptibility for disorders such as autism spectrum disorder (ASD) or schizophrenia is a critical step in the development of better treatments and preventive measures. A large body of literature has investigated the pathophysiology of MIA in rodents. However, a translatability gap plagues pre-clinical research of complex behavioral/developmental diseases and those diseases requiring clinical diagnosis, such as ASD. While ideal for their genetic flexibility, vast reagent toolkit, and practicality, rodent models often lack important elements of ethological validity. Hence, our study aimed to develop and characterize the prenatal MIA model in marmosets. Here, we adapted the well-characterized murine maternal immune activation model. Pregnant dams were administered 5 mg/kg poly-L-lysine stabilized polyinosinic-polycytidylic acid (Poly ICLC) subcutaneously three times during gestation (gestational day 63, 65, and 67). Dams were allowed to deliver naturally with no further experimental treatments. After parturition, offspring were screened for general health and vigor, and individual assessment of communication development and social behavior was measured during neonatal or adolescent periods. Similar to rodent models, offspring subjected to MIA exhibited a disruption in patterns of communication during early development. Assessment of social behavior in a marmoset-modified 3-chamber test at 3 and 9 months of age revealed alterations in social behavior that, in some instances, was sex-dependent. Together, our data indicate that marmosets are an excellent non-human primate model for investigating the neurodevelopmental and behavioral consequences of exposure to prenatal challenges, like MIA. Additional studies are necessary to more completely characterize the effect of prenatal inflammation on marmoset development and explore therapeutic intervention strategies that may be applicable in a clinical setting.

Becoming Stressed: Does the Age Matter? Reviewing the Neurobiological and Socio-Affective Effects of Stress throughout the Lifespan

Social and affective relations occur at every stage of our lives. Impairments in the quality of this “social world” can be exceptionally detrimental and lead to psychopathology or pathological behavior, including schizophrenia, autism spectrum disorder, affective disorders, social phobia or violence, among other things. Exposure to highly stressful or traumatic events, depending on the stage of life in which stress exposure occurs, could severely affect limbic structures, including the amygdala, and lead to alterations in social and affective behaviors. This review summarizes recent findings from stress research and provides an overview of its age-dependent effects on the structure and function of the amygdala, which includes molecular and cellular changes, and how they can trigger deviant social and affective behaviors. It is important to highlight that discoveries in this field may represent a breakthrough both for medical science and for society, as they may help in the development of new therapeutic approaches and prevention strategies in neuropsychiatric disorders and pathological behaviors.

[Immunopsychiatry and SARS-CoV-2 pandemic: Links and possible consequences]

OBJECTIVE

The SARS-CoV-2 (or COVID-19) pandemic has been propagating since December 2019, inducing a drastic increase in the prevalence of anxious and depressive disorders in the general population. Psychological trauma can partly explain these disorders. However, since psychiatric disorders also have an immuno-inflammatory component, the direct effects of the virus on the host's immune system, with a marked inflammatory response, but also the secondary inflammation to these psychosocial stressors, may cause the apparition or the worsening of psychiatric disorders. We describe here the probable immunopsychiatric consequences of the SARS-CoV-2 pandemic, to delineate possible screening actions and care that could be planned.

METHOD

Data from previous pandemics, and existing data on the psychopathological consequences of the SARS-CoV-2 pandemic, allowed us to review the possible immunopsychiatric consequences of the SARS-CoV-2 pandemic, on the gestational environment, with the risk of consecutive neurodevelopmental disorders for the fetus on one hand, on the children and adults directly infected being at increased risks of psychiatric disorders on the other hand.

RESULTS

As in previous pandemics, the activation of the immune system due to psychological stress and/or to infection during pregnancy, might lead to an increased risk of neurodevelopmental disorders for the fetus (schizophrenia and autism spectrum disorders). Furthermore, in individuals exposed to psychological trauma and/or infected by the virus, the risk of psychiatric disorders, especially mood disorders, is probably increased.

CONCLUSION

In this context, preventive measures and specialized care are necessary. Thus, it is important to propose a close follow-up to the individuals who have been infected by the virus, in order to set up the earliest care possible. Likewise, in pregnant women, screening of mood disorders during the pregnancy or the postpartum period must be facilitated. The follow-up of the babies born during the pandemic must be strengthened to screen and care for possible neurodevelopmental disorders.

Maternal Immune Activation Sensitizes Male Offspring Rats to Lipopolysaccharide-Induced Microglial Deficits Involving the Dysfunction of CD200-CD200R and CX3CL1-CX3CR1 Systems

Early life challenges resulting from maternal immune activation (MIA) may exert persistent effects on the offspring, including the development of psychiatric disorders, such as schizophrenia. Recent evidence has suggested that the adverse effects of MIA may be mediated by neuron-microglia crosstalk, particularly CX3CL1-CX3CR1 and CD200-CD200R dyads. Therefore, the present study assessed the behavioural parameters resembling schizophrenia-like symptoms in the adult male offspring of Sprague-Dawley rats that were exposed to MIA and to an additional acute lipopolysaccharide (LPS) challenge in adulthood, according to the "two-hit" hypothesis of schizophrenia. Simultaneously, we aimed to clarify the role of the CX3CL1-CX3CR1 and CD200-CD200R axes and microglial reactivity in the brains of adult offspring subjected to MIA and the "second hit" wit LPS. In the present study, MIA generated a range of behavioural changes in the adult male offspring, including increased exploratory activity and anxiety-like behaviours. The most intriguing finding was observed in the prepulse inhibition (PPI) test, where the deficit in the sensorimotor gating was age-dependent and present only in part of the rats. We were able to distinguish the occurrence of two groups: responsive and non-responsive (without the deficit). Concurrently, based on the results of the biochemical studies, MIA disrupted mainly the CD200-CD200R system, while the changes of the CX3CL1-CX3CR1 axis were less evident in the frontal cortex of adult non-responsive offspring. MIA markedly affected the immune regulators of the CD200-CD200R pathway as we observed an increase in cortical IL-6 release in the responsive group and IL-4 in the non-responsive offspring. Importantly, the "second hit" generated disturbances at the behavioural and biochemical levels mostly in the non-responsive adult animals. Those offspring were characterized both by disturbed PPI and "priming" microglia. Altogether, the exposure to MIA altered the immunomodulatory mechanisms, including the CD200-CD200R axis, in the brain and sensitized animals to subsequent immunological challenges, leading to the manifestation of schizophrenia-like alterations.

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.

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.