The role of maternal immune activation in altering the neurodevelopmental trajectories of offspring: A translational review of neuroimaging studies with implications for autism spectrum disorder and schizophrenia

Large-scale effects of prenatal inflammation and early life circadian disruption in mice: Implications for neurodevelopmental disorders

Around 80 % of individuals with neurodevelopmental disorders such as schizophrenia and autism spectrum disorders experience disruptions in sleep/circadian rhythms. We explored whether environmental circadian disruption interacts with prenatal infection, a risk factor for neurodevelopmental disorders, to induce sex-specific deficits in mice. A maternal immune activation (MIA) protocol was used by injecting pregnant mice with viral mimic poly IC or saline at E9.5. Juvenile/adolescent male and female offspring (3-7 weeks old) were then subjected to a standard light:dark cycle (12:12LD) or to constant light (LL). Significant interactions between treatment (MIA, control) and lighting (12:12LD, LL) were evident in behaviors related to cognition, anxiety, and sociability. This pattern persisted in our RNA sequencing analysis of the dorsal hippocampus, where poly IC exposure resulted in numerous differentially expressed genes (DEGs) in males, while exposure to both poly IC and LL led to a marked reduction in DEGs. Through WGCNA analysis, many significant gene modules were found to be positively associated with poly IC (vs. saline) and LL (vs. LD) in males (fewer in females). Many of the identified hub-bottleneck genes were homologous to human genes associated with sleep/circadian rhythms and neurodevelopmental disorders as revealed by GWA studies. The MIA- and LL-associated modules were enriched in microglia gene signatures, which was paralleled by trends of effects of each of the factors on microglia morphology. In conclusion, in a mouse model of prenatal infection, circadian disruption induced by LL during adolescence acts as a modulator of the effects of MIA at behavioral, cellular, and molecular levels.

Prenatal Maternal Immune Activation with Lipopolysaccharide Accelerates the Developmental Acquisition of Neonatal Reflexes in Rat Offspring Without Affecting Maternal Care Behaviors

Maternal immune activation (MIA)-infection with an immunogen during pregnancy-is linked to an increased risk of neurodevelopmental disorders (NDDs) in offspring. Both MIA and NDDs are associated with developmental delays in offsprings' motor behavior. Therefore, the current study examined the effects of MIA on neonatal reflex development in male and female offspring. Sprague Dawley rats were administered lipopolysaccharide (LPS; 50 μg/mL/kg, i.p.) or saline on embryonic day (E)15 of gestation. The offspring were then tested daily from postnatal day (P)3-P21 to determine their neonatal reflex abilities. The maternal care behaviors of the dam were also quantified on P1-P5, P10, and P15. We found that, regardless of sex, the E15 LPS offspring were able to forelimb grasp, cliff avoid, and right with a correct posture at an earlier postnatal age than the E15 saline offspring did. The E15 LPS offspring also showed better performance of forelimb grasping, hindlimb grasping, righting with correct posture, and walking with correct posture than the E15 saline offspring did. There were no significant differences in maternal licking/grooming, arched-back nursing, non-arched-back nursing, or total nursing across the E15 groups. Overall, these findings suggest that MIA with LPS on E15 accelerates reflex development in offspring without affecting maternal care. This may be explained by the stress acceleration hypothesis, whereby early-life stress accelerates development to promote survival.

The association between maternal immune activation and brain structure and function in human offspring: a systematic review

Maternal immune activation (MIA) during pregnancy, as a result of infectious or inflammatory stimuli, has gained increasing attention for its potential role in adverse child neurodevelopment, with studies focusing on associations in children born preterm. This systematic review summarizes research on the link between several types of prenatal MIA and subsequent child structural and/or functional brain development outcomes. We identified 111 neuroimaging studies in five MIA areas: inflammatory biomarkers (n = 13), chorioamnionitis (n = 18), other types of infections (n = 18), human immunodeficiency virus (HIV) (n = 42), and Zika virus (n = 20). Overall, there was large heterogeneity in the type of MIA exposure examined and in study methodology. Most studies had a prospective single cohort design and mainly focused on potential effects on the brain up to one year after birth. The median sample size was 53 participants. Severe infections, i.e., HIV and Zika virus, were associated with various types of cerebral lesions (e.g., microcephaly, atrophy, or periventricular leukomalacia) that were consistently identified across studies. For less severe infections and chronic inflammation, findings were generally inconsistent and mostly included deviations in white matter structure/function. Current findings have been mainly observed in the infants' brain, presenting an opportunity for future studies to investigate whether these associations persist throughout development. Additionally, the inconsistent findings, encompassing both regions of interest and null results, call into question whether prenatal exposure to less severe infections and chronic inflammation exerts a small effect or no effect on child brain development.

Maternal Immune Activation and Child Brain Development: A Longitudinal Population-Based Multimodal Neuroimaging Study

BACKGROUND

Maternal immune activation (MIA) has been hypothesized to have an adverse effect on child neurodevelopment, but only a few neuroimaging studies have been performed to date, mostly in neonates. In this population-based cohort study, we investigated the association between MIA and multiple neuroimaging modalities depicting brain development from childhood to adolescence.

METHODS

We used data of mother-child pairs from the Generation R Study. To define our exposure, we measured interleukin (IL) 1β, IL-6, IL-17a, IL-23, interferon gamma, and C-reactive protein at 2 time points during pregnancy. Because levels of these 5 cytokines were highly correlated, we were able to compute a cytokine index. We used multiple brain imaging modalities as outcomes, including global and regional measures of brain morphology (structural magnetic resonance imaging, volume; n = 3295), white matter microstructure (diffusion magnetic resonance imaging, fractional anisotropy and mean diffusivity; n = 3267), and functional connectivity (functional magnetic resonance imaging, graph theory measures, and network-level connectivity; n = 2914) in the children at ages 10 and 14 years. We performed mixed effects models using child's age as a continuous time variable.

RESULTS

We found no significant effect of time on any neuroimaging outcomes in children over time, and there was no time × MIA interaction. These associations were similar for the cytokine index, C-reactive protein, and individual cytokines. We observed no evidence for differential effects of timing of prenatal MIA or child sex after multiple testing correction.

CONCLUSIONS

In this longitudinal population-based study, we found no evidence for an association between MIA and child brain development in the general population. Our findings differ from previous research in neonates that have shown structural and functional brain abnormalities after MIA.

ATP8A2 expression is reduced in the mPFC of offspring mice exposed to maternal immune activation and its upregulation ameliorates synapse-associated protein loss and behavioral abnormalities

Prenatal virus infection-induced maternal immune activation (MIA) is linked to a greater risk of neurodevelopmental disorders in offspring. Prenatal exposure to poly(I:C) in pregnant mice is a well-established approach to mimic virus infection-induced MIA, leading to neuropsychiatric disorders and aberrant brain development, especially in the medial prefrontal cortex (mPFC). ATPase phospholipid flippase 8A2 (ATP8A2) is the main phospholipid lipase, expressed in the mPFC and is crucial for maintaining cell membrane stability by flipping phosphatidylserine from the outer leaflet to the inner leaflet of the cell membrane. Atp8a2 knockout or mutation causes a series of phenotypes, including impaired neuronal cell survival, neuroinflammation, altered synaptic plasticity, and behavioral abnormalities. These findings suggest that ATP8A2 expression in the mPFC may be impaired in MIA offspring and that the decrease in ATP8A2 expression may be involved in the development of MIA-induced neuropsychiatric disorders in offspring. No reports addressing this issue have been published. Here, after confirming abnormal affective-/social-related behaviors in adulthood and reduced synapse-associated protein expression on the birth day (P0) and the fourth postnatal day (P4) in the mPFC of MIA offspring that were born to dams exposed prenatally to a single dose of poly(I:C) (10 mg/kg, i.p.), decreased ATP8A2 expression was also observed in the mPFC of MIA offspring at P0 and P4.Upregulating ATP8A2 in the mPFC restored synapse-associated protein levels, along with a partial improvement in the behavioral performance of MIA offspring. Upregulation of ATP8A2 also blocked neuronal phosphatidylserine externalization and eliminated the excitation/inhibition (E/I) imbalance in the mPFC of MIA offspring. This study revealed that the low expression of ATP8A2 following MIA exposure may play a role in mediating abnormal brain development and function in offspring. ATP8A2 potentially represents a novel molecule involved in MIA-induced neuropsychiatric disorders in offspring, and may serve as a novel therapeutic target for the intervention of psychiatric disorders.

Comparison of Gut Microbiota in Two Different Maternal Exposure Models of Autism Spectrum Disorder in Mice

Background

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders with unknown etiology and unclear pathogenesis. Although construction of animal models of ASD using chemical exposure during pregnancy is a mature technique, the gut microbiota of these exposure models induced using different chemicals in mice have not been compared.

Methods

To compare the effects of exposure to different chemicals during pregnancy on the composition of gut microbiota in offspring, we treated Institute of Cancer Research (ICR) mice with lipopolysaccharide (LPS) and valproic acid (VPA) during pregnancy to construct different offspring ASD mouse models. After successful model construction, the gut microbiota of these models were studied.

Results

After adjusting for the random effects of the litter, the two groups showed a significant reduction in social time (social deficits) and an increase in self-grooming behaviors (repetitive and stereotyped behaviors). Gut microbiota analysis revealed significant changes, mostly a decrease, in the abundance of four phyla, 52 genera, and 41 species in the two types of ASD models. Several different gut microbes could be related to the development of ASD.

Conclusions

Chemicals exposure during pregnancy induces ASD-related behavioral abnormalities in offspring mice. Importantly, exposure to different chemicals during pregnancy produces varying degrees of effects on gut microbiota composition in offspring ASD models. This finding can provide a reference for studies on the etiology and pathogenesis of ASD.

From womb to world: The interplay between maternal immune activation, neuroglia, and neurodevelopment

This chapter introduces and discusses maternal immune activation (MIA) as a contributing factor in increasing the risk of neurodevelopmental disorders, particularly in relation to its interactions with neuroglia. Here we first provide an overview of the neuroglia-astroglia, oligodendroglia, microglia, and radial glial cells-and their important role during early brain development and in adulthood. We then present and discuss MIA, followed by a critical overview of inflammatory molecules and temporal stages associated to maternal inflammation during pregnancy. We provide an overview of animal and human models used to mimic and study MIA. Furthermore, we review the possible interaction between MIA and neuroglia, focusing on the current advances in both modeling and therapeutics. Additionally, we discuss and provide preliminary and interesting insights into the most recent pandemic, COVID-19, and how the infection may be associated to MIA and increased risk for neurodevelopmental disorders. Finally, we provide a critical overview of challenges and future opportunities to study how MIA may contribute to higher risk of developing neurodevelopmental disorders.

Immune Alterations in the Intrauterine Environment Shape Offspring Brain Development in a Sex-Specific Manner

Exposure to immune dysregulation in utero or in early life has been shown to increase risk for neuropsychiatric illness. The sources of inflammation can be varied, including acute exposures due to maternal infection or acute stress, or persistent exposures due to chronic stress, obesity, malnutrition, or autoimmune diseases. These exposures may cause subtle alteration in brain development, structure, and function that can become progressively magnified across the lifespan, potentially increasing the likelihood of developing a neuropsychiatric conditions. There is some evidence that males are more susceptible to early-life inflammatory challenges than females. In this review, we discuss the various sources of in utero or early-life immune alteration and the known effects on fetal development with a sex-specific lens. To do so, we leveraged neuroimaging, behavioral, cellular, and neurochemical findings. Gaining clarity about how the intrauterine environment affects offspring development is critically important for informing preventive and early intervention measures that may buffer against the effects of these early-life risk factors.

The Importance of Including Maternal Immune Activation in Animal Models of Hypoxic-Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is a perinatal brain injury that is the leading cause of cerebral palsy, developmental delay, and poor cognitive outcomes in children born at term, occurring in about 1.5 out of 1000 births. The only proven therapy for HIE is therapeutic hypothermia. However, despite this treatment, many children ultimately suffer disability, brain injury, and even death. Barriers to implementation including late diagnosis and lack of resources also lead to poorer outcomes. This demonstrates a critical need for additional treatments for HIE, and to facilitate this, we need translational models that accurately reflect risk factors and interactions present in HIE. Maternal or amniotic infection is a significant risk factor and possible cause of HIE in humans. Maternal immune activation (MIA) is a well-established model of maternal infection and inflammation that has significant developmental consequences largely characterized within the context of neurodevelopmental disorders such as autism spectrum disorder and schizophrenia. MIA can also lead to long-lasting changes within the neuroimmune system, which lead to compounding negative outcomes following a second insult. This supports the importance of understanding the interaction of maternal inflammation and hypoxic-ischemic outcomes. Animal models have been invaluable to understanding the pathophysiology of this injury and to the development of therapeutic hypothermia. However, each model system has its own limitations. Large animal models such as pigs may more accurately represent the brain and organ development and complexity in humans, while rodent models are more cost-effective and offer more possible molecular techniques. Recent studies have utilized MIA or direct inflammation prior to HIE insult. Investigators should thoughtfully consider the risk factors they wish to include in their HIE animal models. In the incorporation of MIA, investigators should consider the type, timing, and dose of the inflammatory stimulus, as well as the timing, severity, and type of hypoxic insult. Using a variety of animal models that incorporate the maternal-placental-fetal system of inflammation will most likely lead to a more robust understanding of the mechanisms of this injury that can guide future clinical decisions and therapies.

Mapping prenatal predictors and neurobehavioral outcomes of an epigenetic marker of neonatal inflammation - A longitudinal population-based study

BACKGROUND

DNA methylation levels at specific sites can be used to proxy C-reactive protein (CRP) levels, providing a potentially more stable and accurate indicator of sustained inflammation and associated health risk. However, its use has been primarily limited to adults or preterm infants, and little is known about determinants for - or offspring outcomes of - elevated levels of this epigenetic proxy in cord blood. The aim of this study was to comprehensively map prenatal predictors and long-term neurobehavioral outcomes of neonatal inflammation, as assessed with an epigenetic proxy of inflammation in cord blood, in the general pediatric population.

METHODS

Our study was embedded in the prospective population-based Generation R Study (n = 2,394). We created a methylation profile score of CRP (MPS-CRP) in cord blood as a marker of neonatal inflammation and validated it against serum CRP levels in mothers during pregnancy, as well as offspring at birth and in childhood. We then examined (i) which factors (previously associated with sustained inflammation) explain variability in MPS-CRP at birth, including a wide range of prenatal lifestyle and clinical conditions, pro-inflammatory exposures, as well as child genetic liability to elevated CRP levels; and (ii) whether MPS-CRP at birth associates with child neurobehavioral outcomes, including global structural MRI and DTI measures (child mean age 10 and 14 years) as well as psychiatric symptoms over time (Child Behavioral Checklist, at mean age 1.5, 3, 6, 10 and 14 years).

RESULTS

MPS-CRP at birth was validated with serum CRP in cord blood (cut-off > 1 mg/L) (AUC = 0.72). Prenatal lifestyle pro-inflammatory factors explained a small part (i.e., < 5%) of the variance in the MPS-CRP at birth. No other prenatal predictor or the polygenic score of CRP in the child explained significant variance in the MPS-CRP at birth. The MPS-CRP at birth prospectively associated with a reduction in global fractional anisotropy over time on mainly a nominal threshold (β = -0.014, SE = 0.007, p = 0.032), as well as showing nominal associations with structural differences (amygdala [(β = 0.016, SE = 0.006, p = 0.010], cerebellum [(β = -0.007, SE = 0.003, p = 0.036]). However, no associations with child psychiatric symptoms were observed.

CONCLUSION

Prenatal exposure to lifestyle-related pro-inflammatory factors was the only prenatal predictor that accounted for some of the individual variability in MPS-CRP levels at birth. Further, while the MPS-CRP prospectively associated with white matter alterations over time, no associations were observed at the behavioral level. Thus, the relevance and potential utility of using epigenetic data as a marker of neonatal inflammation in the general population remain unclear. In the future, the use of epigenetic proxies for a wider range of immune markers may lend further insights into the relationship between neonatal inflammation and adverse neurodevelopment within the general pediatric population.

Maternal prenatal immune activation associated with brain tissue microstructure and metabolite concentrations in newborn infants

Few human studies have assessed the association of prenatal maternal immune activation (MIA) with measures of brain development and psychiatric risk in newborn offspring. Our goal was to identify the effects of MIA during the 2nd and 3rd trimesters of pregnancy on newborn measures of brain metabolite concentrations, tissue microstructure, and motor development. This was a prospective longitudinal cohort study conducted with nulliparous pregnant women who were aged 14 to 19 years and recruited in their 2nd trimester, as well as their children who were followed through 14 months of age. MIA was indexed by maternal interleukin-6 (IL-6) and C-reactive protein (CRP) in both trimesters of pregnancy. Primary outcomes included: (1) newborn brain metabolite concentrations as ratios to creatine (N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr) measured using Magnetic Resonance Spectroscopy; (2) newborn fractional anisotropy and mean diffusivity, measured using Diffusion Tensor Imaging; and (3) indices of motor development, assessed prenatally and postnatally at ages 4- and 14-months. Maternal IL-6 and CRP levels associated significantly with both metabolites in the putamen, thalamus, insula, and the internal capsule. Maternal IL-6 associated significantly with fractional anisotropy in the putamen, caudate, thalamus, insula, and precuneus, and with mean diffusivity in the inferior parietal and middle temporal gyrus. CRP associated significantly with fractional anisotropy in the thalamus, insula, and putamen. Significant associations were found in common regions across imaging modalities, though the direction of associations differed by immune marker. In addition, both maternal IL-6 and CRP (in both trimesters) prenatally associated significantly with offspring motor development at 4- and 14-months of age. The left thalamus mediated effects of IL-6 on postnatal motor development. These findings demonstrate that levels of MIA in mid- to late pregnancy in a generally healthy sample associate with tissue characteristics in newborn brain regions that primarily support motor integration and coordination, as well as behavioral regulation. Those brain effects may contribute to differences in motor development.

The Complex World of Kynurenic Acid: Reflections on Biological Issues and Therapeutic Strategy

It has been unequivocally established that kynurenic acid has a number of actions in a variety of cells and tissues, raising, in principle, the possibility of targeting its generation, metabolism or sites of action to manipulate those effects to a beneficial therapeutic end. However, many basic aspects of the biology of kynurenic acid remain unclear, potentially leading to some confusion and misinterpretations of data. They include questions of the source, generation, targets, enzyme expression, endogenous concentrations and sites of action. This essay is intended to raise and discuss many of these aspects as a source of reference for more balanced discussion. Those issues are followed by examples of situations in which modulating and correcting kynurenic acid production or activity could bring significant therapeutic benefit, including neurological and psychiatric conditions, inflammatory diseases and cell protection. More information is required to obtain a clear overall view of the pharmacological environment relevant to kynurenic acid, especially with respect to the active concentrations of kynurenine metabolites in vivo and changed levels in disease. The data and ideas presented here should permit a greater confidence in appreciating the sites of action and interaction of kynurenic acid under different local conditions and pathologies, enhancing our understanding of kynurenic acid itself and the many clinical conditions in which manipulating its pharmacology could be of clinical value.

Prenatal psychological distress and 11β-HSD2 gene expression in human placentas: Systematic review and meta-analysis

BACKGROUND

The placenta acts as a buffer to regulate the degree of fetal exposure to maternal cortisol through the 11-Beta Hydroxysteroid Dehydrogenase isoenzyme type 2 (11-β HSD2) enzyme. We conducted a systematic review and meta-analysis to assess the effect of prenatal psychological distress (PPD) on placental 11-β HSD2 gene expression and explore the related mechanistic pathways involved in fetal neurodevelopment.

METHODS

We searched PubMed, Embase, Scopus, APA PsycInfo®, and ProQuest Dissertations for observational studies assessing the association between PPD and 11-β HSD2 expression in human placentas. Adjusted regression coefficients (β) and corresponding 95% confidence intervals (CIs) were pooled based on three contextual PPD exposure groups: prenatal depression, anxiety symptoms, and perceived stress.

RESULTS

Of 3159 retrieved records, sixteen longitudinal studies involving 1869 participants across seven countries were included. Overall, exposure to PPD disorders showed weak negative associations with the placental 11-β HSD2 gene expression as follows: prenatal depression (β -0.01, 95% CI 0.05-0.02, I2=0%), anxiety symptoms (β -0.02, 95% CI 0.06-0.01, I2=0%), and perceived stress (β -0.01 95% CI 0.06-0.04, I2=62.8%). Third-trimester PPD exposure was more frequently associated with lower placental 11-β HSD2 levels. PPD and placental 11-β HSD2 were associated with changes in cortisol reactivity and the development of adverse health outcomes in mothers and children. Female-offspring were more vulnerable to PPD exposures.

CONCLUSION

The study presents evidence of a modest role of prenatal psychological distress in regulating placental 11-β HSD2 gene expression. Future prospective cohorts utilizing larger sample sizes or advanced statistical methods to enhance the detection of small effect sizes should be planned. Additionally, controlling for key predictors such as the mother's ethnicity, trimester of PPD exposure, mode of delivery, and infant sex is crucial for valid exploration of PPD effects on fetal programming.

Maternal immune activation with toll-like receptor 7 agonist during mid-gestation alters juvenile and adult developmental milestones and behavior

Infections during pregnancy are associated with increased risk for adult neuropsychiatric disease, such as major depressive disorder, schizophrenia, and autism spectrum disorder. In mouse models of maternal immune activation (MIA), different toll-like receptors (TLRs) are stimulated to initiate inflammatory responses in mother and fetus. The goal of this study was to determine sex-dependent aspects of MIA using a TLR7/8 agonist, Resiquimod (RQ), on neurodevelopment. RQ was administered to timed-pregnant mice on embryonic day (E) 12.5. At E15, maternal/fetal plasma cytokines were measured by enzyme-linked immunosorbent assay (ELISA). Maternal cytokines interleukin (IL)-6 and IL-10 were higher while tumor necrosis factor (TNF)-α and IL-17 were lower in pregnant dams exposed to RQ. Fetal cytokines (E15) were altered at the same timepoint with fetal plasma IL-6 and IL-17 greater after RQ compared to vehicle, while IL-10 and TNF-α were higher in male fetuses but not female. Other timed-pregnant dams were allowed to give birth. MIA with RQ did not alter the female to male ratio of offspring born per litter. Body weights were reduced significantly in both sexes at birth, and over the next 5 weeks. Offspring from RQ-injected mothers opened their eyes 5 days later than controls. Similarly, female offspring from RQ-injected mothers exhibited pubertal delay based on vaginal opening 2-3 days later than control females. On the behavioral side, juvenile and adult male and female MIA offspring exhibited less social-like behavior in a social interaction test. Anhedonia-like behavior was greater in MIA adult female mice. This study provides support for sex-dependent influences of fetal antecedents for altered brain development and behavioral outputs that could be indicative of increased susceptibility for adult disorders through immune mechanisms. Future studies are needed to determine neural cellular and molecular mechanisms for such programming effects.

Examining longitudinal associations between prenatal exposure to infections and child brain morphology

BACKGROUND

Maternal infection during pregnancy has been identified as a prenatal risk factor for the later development of psychopathology in exposed offspring. Neuroimaging data collected during childhood has suggested a link between prenatal exposure to maternal infection and child brain structure and function, potentially offering a neurobiological explanation for the emergence of psychopathology. Additionally, preclinical studies utilizing repeated measures of neuroimaging data suggest that effects of prenatal maternal infection on the offspring's brain may normalize over time (i.e., catch-up growth). However, it remains unclear whether exposure to prenatal maternal infection in humans is related to long-term differential neurodevelopmental trajectories. Hence, this study aimed to investigate the association between prenatal exposure to infections on child brain development over time using repeated measures MRI data.

METHODS

We leveraged data from a population-based cohort, Generation R, in which we examined prospectively assessed self-reported infections at each trimester of pregnancy (N = 2,155). We further used three neuroimaging assessments (at mean ages 8, 10 and 14) to obtain cortical and subcortical measures of the offspring's brain morphology with MRI. Hereafter, we applied linear mixed-effects models, adjusting for several confounding factors, to estimate the association of prenatal maternal infection with child brain development over time.

RESULTS

We found that prenatal exposure to infection in the third trimester was associated with a slower decrease in volumes of the pars orbitalis, rostral anterior cingulate and superior frontal gyrus, and a faster increase in the middle temporal gyrus. In the temporal pole we observed a divergent pattern, specifically showing an increase in volume in offspring exposed to more infections compared to a decrease in volume in offspring exposed to fewer infections. We further observed associations in other frontal and temporal lobe structures after exposure to infections in any trimester, though these did not survive multiple testing correction.

CONCLUSIONS

Our results suggest that prenatal exposure to infections in the third trimester may be associated with slower age-related growth in the regions: pars orbitalis, rostral anterior cingulate and superior frontal gyrus, and faster age-related growth in the middle temporal gyrus across childhood, suggesting a potential sensitive period. Our results might be interpreted as an extension of longitudinal findings from preclinical studies, indicating that children exposed to prenatal infections could exhibit catch-up growth. However, given the lack of differences in brain volume between various infection groups at baseline, there may instead be either a longitudinal deviation or a subtle temporal deviation. Subsequent well-powered studies that extend into the period of full brain development (∼25 years) are needed to confirm whether the observed phenomenon is indeed catch-up growth, a longitudinal deviation, or a subtle temporal deviation.

Therapeutic potential of gamma entrainment using sensory stimulation for cognitive symptoms associated with schizophrenia

Schizophrenia is a complex neuropsychiatric disorder with significant morbidity. Treatment options that address the spectrum of symptoms are limited, highlighting the need for innovative therapeutic approaches. Gamma Entrainment Using Sensory Stimulation (GENUS) is an emerging treatment for neuropsychiatric disorders that uses sensory stimulation to entrain impaired oscillatory network activity and restore brain function. Aberrant oscillatory activity often underlies the symptoms experienced by patients with schizophrenia. We propose that GENUS has therapeutic potential for schizophrenia. This paper reviews the current status of schizophrenia treatment and explores the use of sensory stimulation as an adjunctive treatment, specifically through gamma entrainment. Impaired gamma frequency entrainment is observed in patients, particularly in response to auditory and visual stimuli. Thus, sensory stimulation, such as music listening, may have therapeutic potential for individuals with schizophrenia. GENUS holds novel therapeutic potential to improve the lives of individuals with schizophrenia, but further research is required to determine the efficacy of GENUS, optimize its delivery and therapeutic window, and develop strategies for its implementation in specific patient populations.

Giftedness and atypical sexual differentiation: enhanced perceptual functioning through estrogen deficiency instead of androgen excess

Syndromic autism spectrum conditions (ASC), such as Klinefelter syndrome, also manifest hypogonadism. Compared to the popular Extreme Male Brain theory, the Enhanced Perceptual Functioning model explains the connection between ASC, savant traits, and giftedness more seamlessly, and their co-emergence with atypical sexual differentiation. Overexcitability of primary sensory inputs generates a relative enhancement of local to global processing of stimuli, hindering the abstraction of communication signals, in contrast to the extraordinary local information processing skills in some individuals. Weaker inhibitory function through gamma-aminobutyric acid type A (GABAA) receptors and the atypicality of synapse formation lead to this difference, and the formation of unique neural circuits that process external information. Additionally, deficiency in monitoring inner sensory information leads to alexithymia (inability to distinguish one's own emotions), which can be caused by hypoactivity of estrogen and oxytocin in the interoceptive neural circuits, comprising the anterior insular and cingulate gyri. These areas are also part of the Salience Network, which switches between the Central Executive Network for external tasks and the Default Mode Network for self-referential mind wandering. Exploring the possibility that estrogen deficiency since early development interrupts GABA shift, causing sensory processing atypicality, it helps to evaluate the co-occurrence of ASC with attention deficit hyperactivity disorder, dyslexia, and schizophrenia based on phenotypic and physiological bases. It also provides clues for understanding the common underpinnings of these neurodevelopmental disorders and gifted populations.

Maternal immune activation and estrogen receptor modulation induce sex-specific dopamine-related behavioural and molecular alterations in adult rat offspring

Dopamine dysregulation contributes to psychosis and cognitive deficits in schizophrenia that can be modelled in rodents by inducing maternal immune activation (MIA). The selective estrogen receptor (ER) modulator, raloxifene, can improve psychosis and cognition in men and women with schizophrenia. However, few studies have examined how raloxifene may exert its therapeutic effects in mammalian brain in both sexes during young adulthood (age relevant to most prevalent age at diagnosis). Here, we tested the extent to which raloxifene alters dopamine-related behaviours and brain transcripts in young adult rats, both control and MIA-exposed females and males. We found that raloxifene increased amphetamine (AMPH)-induced locomotor activity in female controls, and in contrast, raloxifene reduced AMPH-induced locomotor activity in male MIA offspring. We did not detect overt prepulse inhibition (PPI) deficits in female or male MIA offspring, yet raloxifene enhanced PPI in male MIA offspring. Whereas, raloxifene ameliorated increased startle responsivity in female MIA offspring. In the substantia nigra (SN), we found reduced Drd2s mRNA in raloxifene-treated female offspring with or without MIA, and increased Comt mRNA in placebo-treated male MIA offspring relative to placebo-treated controls. These data demonstrate an underlying dopamine dysregulation in MIA animals that can become more apparent with raloxifene treatment, and may involve selective alterations in dopamine receptor levels and dopamine breakdown processes in the SN. Our findings support sex-specific, differential behavioural responses to ER modulation in MIA compared to control offspring, with beneficial effects of raloxifene treatment on dopamine-related behaviours relevant to schizophrenia found in male MIA offspring only.

Early-life immune activation is a vulnerability factor for adult epileptogenesis in neurofibromatosis type 1 in male mice

Introduction

Patients with Neurofibromatosis type 1 (NF1), the most common neurocutaneous disorder, can develop several neurological manifestations that include cognitive impairments and epilepsy over their lifetime. It is unclear why certain patients with NF1 develop these conditions while others do not. Early-life immune activation promotes later-life seizure susceptibility, neurocognitive impairments, and leads to spontaneous seizures in some animal models of neurodevelopmental disorders, but the central nervous system immune profile and the enduring consequences of early-life immune activation on the developmental trajectory of the brain in NF1 have not yet been explored. We tested the hypothesis that early-life immune activation promotes the development of spatial memory impairments and epileptogenesis in a mouse model of NF1.

Methods

Male wild-type (WT) and Nf1+/- mice received systemic lipopolysaccharide (LPS) or saline at post-natal day 10 and were assessed in adulthood for learning and memory deficits in the Barnes maze and underwent EEG recordings to look for spontaneous epileptiform abnormalities and susceptibility to challenge with pentylenetetrazole (PTZ).

Results

Whereas early-life immune activation by a single injection of LPS acutely elicited a comparable brain cytokine signature in WT and Nf1+/- mice, it promoted spontaneous seizure activity in adulthood only in the Nf1+/- mice. Early-life immune activation affected susceptibility to PTZ-induced seizures similarly in both WT and Nf1+/-mice. There was no effect on spatial learning and memory regardless of mouse genotype.

Discussion

Our findings suggest second-hit environmental events such as early-life immune activation may promote epileptogenesis in the Nf1+/- mouse and may be a risk-factor for NF1-associated epilepsy.

Congenital infectious encephalopathies from the intrapartum period to postnatal life

Congenital infections are a common but often underrecognized cause of fetal brain abnormalities, as well as fetal-neonatal morbidity and mortality, that should be considered by all healthcare professionals providing neurological care to fetuses and newborns. Maternal infection with various pathogens (cytomegalovirus, Toxoplasmosis, Rubella virus, Parvovirus B19, lymphocytic choriomeningitis virus, syphilis, Zika virus, varicella zoster virus) during pregnancy can be transmitted to the developing fetus, which can cause multisystem dysfunction and destructive or malformative central nervous system lesions. These can be recognized on fetal and neonatal imaging, including ultrasound and MRI. Imaging and clinical features often overlap, but some distinguishing features can help identify specific pathogens and guide subsequent testing strategies. Some pathogens can be specifically treated, and others can be managed with targeted interventions or symptomatic therapy based on expected complications. Neurological and neurodevelopmental complications related to congenital infections vary widely and are likely driven by a combination of pathophysiologic factors, alone or in combination. These include direct invasion of the fetal central nervous system by pathogens, inflammation of the maternal-placental-fetal triad in response to infection, and long-term effects of immunogenic and epigenetic changes in the fetus in response to maternal-fetal infection. Congenital infections and their neurodevelopmental impacts should be seen as an issue of public health policy, given that infection and the associated complications disproportionately affect woman and children from low- and middle-income countries and those with lower socio-economic status in high-income countries. Congenital infections may be preventable and treatable, which can improve long-term neurodevelopmental outcomes in children.

Impaired erythropoietin-producing hepatocellular B receptors signaling in the prefrontal cortex and hippocampus following maternal immune activation in male rats

An environmental risk factor for schizophrenia (SZ) is maternal infection, which exerts longstanding effects on the neurodevelopment of offspring. Accumulating evidence suggests that synaptic disturbances may contribute to the pathology of the disease, but the underlying molecular mechanisms remain poorly understood. Erythropoietin-producing hepatocellular B (EphB) receptor signaling plays an important role in synaptic plasticity by regulating the formation and maturation of dendritic spines and regulating excitatory neurotransmission. We examined whether EphB receptors and downstream associated proteins are susceptible to environmental risk factors implicated in the etiology of synaptic disturbances in SZ. Using an established rodent model, which closely imitates the characteristics of SZ, we observed the behavioral performance and synaptic structure of male offspring in adolescence and early adulthood. We then analyzed the expression of EphB receptors and associated proteins in the prefrontal cortex and hippocampus. Maternal immune activation offspring showed significantly progressive cognitive impairment and pre-pulse inhibition deficits together with an increase in the expression of EphB2 receptors and NMDA receptor subunits. We also found changes in EphB receptor downstream signaling, in particular, a decrease in phospho-cofilin levels which may explain the reduced dendritic spine density. Besides, we found that the AMPA glutamate, another glutamate ionic receptor associated with cofilin, decreased significantly in maternal immune activation offspring. Thus, alterations in EphB signaling induced by immune activation during pregnancy may underlie disruptions in synaptic plasticity and function in the prefrontal cortex and hippocampus associated with behavioral and cognitive impairment. These findings may provide insight into the mechanisms underlying SZ.

Altered Developmental Trajectory in Male and Female Rats in a Prenatal Valproic Acid Exposure Model of Autism Spectrum Disorder

Early motor and sensory developmental delays precede Autism Spectrum Disorder (ASD) diagnosis and may serve as early indicators of ASD. The literature on sensorimotor development in animal models is sparse, male centered, and has mixed findings. We characterized early development in a prenatal valproic acid (VPA) model of ASD and found sex-specific developmental delays in VPA rats. We created a developmental composite score combining 15 test readouts, yielding a reliable gestalt measure spanning physical, sensory, and motor development, that effectively discriminated between VPA and control groups. Considering the heterogeneity in ASD phenotype, the developmental composite offers a robust metric that can enable comparison across different animal models of ASD and can serve as an outcome measure for early intervention studies.

Arketamine for cognitive impairment in psychiatric disorders

Cognitive impairment has been observed in patients with various psychiatric disorders, including schizophrenia, major depressive disorder (MDD), and bipolar disorder (BD). Although modern therapeutic drugs can improve certain symptoms (i.e., psychosis, depression) in these patients, these drugs have not been found to improve cognitive impairment. The N-methyl-D-aspartate receptor antagonist (R,S)-ketamine has attracted attention as a rapidly acting antidepressant. In addition to its robust antidepressant effects, (R,S)-ketamine has been suggested to improve cognitive impairment in patients with MDD and BD, despite causing cognitive impairment in healthy control subjects. (R,S)-ketamine is a racemic mixture of equal amounts of (R)-ketamine (or arketamine) and (S)-ketamine (or esketamine). Arketamine has been found to have more potent antidepressant-like actions than esketamine in rodents. Interestingly, arketamine, but not esketamine, has been suggested to improve phencyclidine-induced cognitive deficits in mice. Furthermore, arketamine has been suggested to ameliorate cognitive deficits in rodent offspring after maternal immune activation. In the current article, it is proposed that arketamine has therapeutic potential for treating cognitive impairment in patients with psychiatric disorders. Additionally, the potential role of the gut-microbiome-brain axis in cognitive impairment in psychiatric disorders is discussed.

Extracellular free water elevations are associated with brain volume and maternal cytokine response in a longitudinal nonhuman primate maternal immune activation model

Maternal infection has emerged as an important environmental risk factor for neurodevelopmental disorders, including schizophrenia and autism spectrum disorders. Animal model systems of maternal immune activation (MIA) suggest that the maternal immune response plays a significant role in the offspring's neurodevelopment and behavioral outcomes. Extracellular free water is a measure of freely diffusing water in the brain that may be associated with neuroinflammation and impacted by MIA. The present study evaluates the brain diffusion characteristics of male rhesus monkeys (Macaca mulatta) born to MIA-exposed dams (n = 14) treated with a modified form of the viral mimic polyinosinic:polycytidylic acid at the end of the first trimester. Control dams received saline injections at the end of the first trimester (n = 10) or were untreated (n = 4). Offspring underwent diffusion MRI scans at 6, 12, 24, 36, and 45 months. Offspring born to MIA-exposed dams showed significantly increased extracellular free water in cingulate cortex gray matter starting as early as 6 months of age and persisting through 45 months. In addition, offspring gray matter free water in this region was significantly correlated with the magnitude of the maternal IL-6 response in the MIA-exposed dams. Significant correlations between brain volume and extracellular free water in the MIA-exposed offspring also indicate converging, multimodal evidence of the impact of MIA on brain development. These findings provide strong evidence for the construct validity of the nonhuman primate MIA model as a system of relevance for investigating the pathophysiology of human neurodevelopmental psychiatric disorders. Elevated free water in individuals exposed to immune activation in utero could represent an early marker of a perturbed or vulnerable neurodevelopmental trajectory.

Long-term effects of prophylactic MgSO4 in maternal immune activation rodent model at adolescence and adulthood

The effects of MgSO₄ as an anti-inflammatory agent in pregnant women have been investigated in the last few years. Infections can cause an inflammatory reaction involving the placenta membranes and amniotic cavity. They may have short-term effects on the mother and her fetuses, like preterm birth, cerebral palsy, and developmental delay. Despite the alleged advantages of MgSO₄ as a neuroprotective agent in the preterm brain, the long-term molecular and behavioral function of MgSO₄ has not been fully elucidated. Here, we investigated the long-term effect of antenatal MgSO₄ , during late gestation, on offspring's behavior focusing on cognitive function, motor activity, and social cognition in adolescence and adulthood, and explored its influence on brain gene expression (e.g., ErbB signaling, pro-inflammatory, and dopaminergic markers) in adulthood. A significant abnormal exploratory behavior of offspring of MgSO₄ -treated dams was found compared to the control group in both adolescence and adulthood. Furthermore, we found that adult females exposed to MgSO₄ under inflammation displayed working and recognition memory impairment. A reduction in IL-6 expression was detected in the prefrontal cortex, and hippocampus specimens derived from LPS-Mg-treated group. In contrast, an imbalanced expression of dopamine 1 and 2 receptors was detected only in prefrontal cortex specimens. Besides, we found that MgSO₄ ameliorated the overexpression of the Nrg1 and Erbb4 receptors induced by LPS in the hippocampus. Thus, MgSO₄ treatment for preventing brain injuries can adversely affect offspring cognition behavior later in life, depending on the sex and age of the offspring.

Investigating the "two-hit hypothesis": Effects of prenatal maternal immune activation and adolescent cannabis use on neurodevelopment in mice

Prenatal exposure to maternal immune activation (MIA) and chronic adolescent cannabis use are both risk factors for neuropsychiatric disorders. However, exposure to a single risk factor may not result in major mental illness, indicating that multiple exposures may be required for illness onset. Here, we examine whether combined exposure to prenatal MIA and adolescent delta-9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis, lead to enduring neuroanatomical and behavioural changes in adulthood. Mice were prenatally exposed to viral mimetic, poly I:C (5 mg/kg), or vehicle at gestational day (GD) 9, and postnatally exposed to chronic THC (5 mg/kg, intraperitoneal) or vehicle during adolescence (postnatal day [PND]28-45). Longitudinal magnetic resonance imaging (MRI) was performed pre-treatment, PND 25, post-treatment, PND 50, and in adulthood, PND85, followed by behavioural tests for anxiety-like, social, and sensorimotor gating. Post-mortem assessment of cannabinoid (CB)1 and 2 receptor expressing cells was performed in altered regions identified by MRI (anterior cingulate and somatosensory cortices, striatum, and hippocampus). Subtle deviations in neurodevelopmental trajectory and subthreshold anxiety-like behaviours were observed in mice exposed to both risk factors. Sex-dependent effects were observed in patterns of shared brain-behaviour covariation, indicative of potential sex differences in response to MIA and THC. Density of CB1 and CB2 receptor positive cells was significantly decreased in all mice exposed to MIA, THC, or both. These findings suggest that there may be a cumulative effect of risk factor exposure on gross neuroanatomical development, and that the endocannabinoid system may be sensitive to both prenatal MIA, adolescent THC, or the combination.

Maternal immune activation as an epidemiological risk factor for neurodevelopmental disorders: Considerations of timing, severity, individual differences, and sex in human and rodent studies

Epidemiological evidence suggests that one's risk of being diagnosed with a neurodevelopmental disorder (NDD)-such as autism, ADHD, or schizophrenia-increases significantly if their mother had a viral or bacterial infection during the first or second trimester of pregnancy. Despite this well-known data, little is known about how developing neural systems are perturbed by events such as early-life immune activation. One theory is that the maternal immune response disrupts neural processes important for typical fetal and postnatal development, which can subsequently result in specific and overlapping behavioral phenotypes in offspring, characteristic of NDDs. As such, rodent models of maternal immune activation (MIA) have been useful in elucidating neural mechanisms that may become dysregulated by MIA. This review will start with an up-to-date and in-depth, critical summary of epidemiological data in humans, examining the association between different types of MIA and NDD outcomes in offspring. Thereafter, we will summarize common rodent models of MIA and discuss their relevance to the human epidemiological data. Finally, we will highlight other factors that may interact with or impact MIA and its associated risk for NDDs, and emphasize the importance for researchers to consider these when designing future human and rodent studies. These points to consider include: the sex of the offspring, the developmental timing of the immune challenge, and other factors that may contribute to individual variability in neural and behavioral responses to MIA, such as genetics, parental age, the gut microbiome, prenatal stress, and placental buffering.

Neurodevelopmental patterns of early postnatal white matter maturation represent distinct underlying microstructure and histology

Cerebral white matter undergoes a rapid and complex maturation during the early postnatal period. Prior magnetic resonance imaging (MRI) studies of early postnatal development have often been limited by small sample size, single-modality imaging, and univariate analytics. Here, we applied nonnegative matrix factorization, an unsupervised multivariate pattern analysis technique, to T2w/T1w signal ratio maps from the Developing Human Connectome Project (n = 342 newborns) revealing patterns of coordinated white matter maturation. These patterns showed divergent age-related maturational trajectories, which were replicated in another independent cohort (n = 239). Furthermore, we showed that T2w/T1w signal variations in these maturational patterns are explained by differential contributions of white matter microstructural indices derived from diffusion-weighted MRI. Finally, we demonstrated how white matter maturation patterns relate to distinct histological features by comparing our findings with postmortem late fetal/early postnatal brain tissue staining. Together, these results delineate concise and effective representation of early postnatal white matter reorganization.

Impact of Maternal Immune Activation on Nonhuman Primate Prefrontal Cortex Development: Insights for Schizophrenia

Late adolescence is a period of dynamic change in the brain as humans learn to navigate increasingly complex environments. In particular, prefrontal cortical (PFC) regions undergo extensive remodeling as the brain is fine-tuned to orchestrate cognitive control over attention, reasoning, and emotions. Late adolescence also presents a uniquely vulnerable period as neurodevelopmental illnesses, such as schizophrenia, become evident and worsen into young adulthood. Challenges in early development, including prenatal exposure to infection, may set the stage for a cascade of maladaptive events that ultimately result in aberrant PFC connectivity and function before symptoms emerge. A growing body of research suggests that activation of the mother's immune system during pregnancy may act as a disease primer, in combination with other environmental and genetic factors, contributing to an increased risk of neurodevelopmental disorders, including schizophrenia. Animal models provide an invaluable opportunity to examine the course of brain and behavioral changes in offspring exposed to maternal immune activation (MIA). Although the vast majority of MIA research has been carried out in rodents, here we highlight the translational utility of the nonhuman primate (NHP) as a model species more closely related to humans in PFC structure and function. In this review, we consider the protracted period of brain and behavioral maturation in the NHP, describe emerging findings from MIA NHP offspring in the context of rodent preclinical models, and lastly explore the translational relevance of the NHP MIA model to expand understanding of the etiology and developmental course of PFC pathology in schizophrenia.

Inflammation and Autophagy: A Convergent Point between Autism Spectrum Disorder (ASD)-Related Genetic and Environmental Factors: Focus on Aluminum Adjuvants

Autism spectrum disorder (ASD), schizophrenia, and bipolar disorder are genetically complex and heterogeneous neurodevelopmental disorders (NDDs) resulting from genetic factors and gene-environment (GxE) interactions for which onset occurs in early brain development. Recent progress highlights the link between ASD and (i) immunogenetics, neurodevelopment, and inflammation, and (ii) impairments of autophagy, a crucial neurodevelopmental process involved in synaptic pruning. Among various environmental factors causing risk for ASD, aluminum (Al)-containing vaccines injected during critical periods have received special attention and triggered relevant scientific questions. The aim of this review is to discuss the current knowledge on the role of early inflammation, immune and autophagy dysfunction in ASD as well as preclinical studies which question Al adjuvant impacts on brain and immune maturation. We highlight the most recent breakthroughs and the lack of epidemiological, pharmacokinetic and pharmacodynamic data constituting a "scientific gap". We propose additional research, such as genetic studies that could contribute to identify populations at genetic risk, improving diagnosis, and potentially the development of new therapeutic tools.

Soluble Epoxide Hydrolase as a Therapeutic Target for Neuropsychiatric Disorders

It has been found that soluble epoxide hydrolase (sEH; encoded by the EPHX2 gene) in the metabolism of polyunsaturated fatty acids (PUFAs) plays a key role in inflammation, which, in turn, plays a part in the pathogenesis of neuropsychiatric disorders. Meanwhile, epoxy fatty acids such as epoxyeicosatrienoic acids (EETs), epoxyeicosatetraenoic acids (EEQs), and epoxyeicosapentaenoic acids (EDPs) have been found to exert neuroprotective effects in animal models of neuropsychiatric disorders through potent anti-inflammatory actions. Soluble expoxide hydrolase, an enzyme present in all living organisms, metabolizes epoxy fatty acids into the corresponding dihydroxy fatty acids, which are less active than the precursors. In this regard, preclinical findings using sEH inhibitors or Ephx2 knock-out (KO) mice have indicated that the inhibition or deficiency of sEH can have beneficial effects in several models of neuropsychiatric disorders. Thus, this review discusses the current findings of the role of sEH in neuropsychiatric disorders, including depression, autism spectrum disorder (ASD), schizophrenia, Parkinson’s disease (PD), and stroke, as well as the potential mechanisms underlying the therapeutic effects of sEH inhibitors.

Differential effects of early or late exposure to prenatal maternal immune activation on mouse embryonic neurodevelopment

Exposure to maternal immune activation (MIA) in utero is a risk factor for neurodevelopmental and psychiatric disorders. MIA-induced deficits in adolescent and adult offspring have been well characterized; however, less is known about the effects of MIA exposure on embryo development. To address this gap, we performed high-resolution ex vivo MRI to investigate the effects of early (gestational day [GD]9) and late (GD17) MIA exposure on embryo (GD18) brain structure. We identify striking neuroanatomical changes in the embryo brain, particularly in the late-exposed offspring. We further examined the putative neuroanatomical underpinnings of MIA timing in the hippocampus using electron microscopy and identified differential effects due to MIA timing. An increase in apoptotic cell density was observed in the GD9-exposed offspring, while an increase in the density of neurons and glia with ultrastructural features reflective of increased neuroinflammation and oxidative stress was observed in GD17-exposed offspring, particularly in females. Overall, our findings integrate imaging techniques across different scales to identify differential impact of MIA timing on the earliest stages of neurodevelopment.

Autism spectrum disorder and schizophrenia: An updated conceptual review

Autism spectrum disorder (ASD) and schizophrenia (SCZ) are separate disorders, with distinct clinical profiles and natural histories. ASD, typically diagnosed in childhood, is characterized by restricted or repetitive interests or behaviors and impaired social communication, and it tends to have a stable course. SCZ, typically diagnosed in adolescence or adulthood, is characterized by hallucinations and delusions, and tends to be associated with declining function. However, youth with ASD are three to six times more likely to develop SCZ than their neurotypical counterparts, and increasingly, research has shown that ASD and SCZ converge at several levels. We conducted a systematic review of studies since 2013 relevant to understanding this convergence, and present here a narrative synthesis of key findings, which we have organized into four broad categories: symptoms and behavior, perception and cognition, biomarkers, and genetic and environmental risk. We then discuss opportunities for future research into the phenomenology and neurobiology of overlap between ASD and SCZ. Understanding this overlap will allow for researchers, and eventually clinicians, to understand the factors that may make a child with ASD vulnerable to developing SCZ. LAY SUMMARY: Autism spectrum disorder and schizophrenia are distinct diagnoses, but people with autism and people with schizophrena share several characteristics. We review recent studies that have examined these areas of overlap, and discuss the kinds of studies we will need to better understand how these disorders are related. Understanding this will be important to help us identify which autistic children are at risk of developing schizophrenia.

Maternal Immune Activation during Pregnancy Alters Postnatal Brain Growth and Cognitive Development in Nonhuman Primate Offspring

Human epidemiological studies implicate exposure to infection during gestation in the etiology of neurodevelopmental disorders. Animal models of maternal immune activation (MIA) have identified the maternal immune response as the critical link between maternal infection and aberrant offspring brain and behavior development. Here we evaluate neurodevelopment of male rhesus monkeys (Macaca mulatta) born to MIA-treated dams (n = 14) injected with a modified form of the viral mimic polyinosinic:polycytidylic acid at the end of the first trimester. Control dams received saline injections at the same gestational time points (n = 10) or were untreated (n = 4). MIA-treated dams exhibited a strong immune response as indexed by transient increases in sickness behavior, temperature, and inflammatory cytokines. Although offspring born to control or MIA-treated dams did not differ on measures of physical growth and early developmental milestones, the MIA-treated animals exhibited subtle changes in cognitive development and deviated from species-typical brain growth trajectories. Longitudinal MRI revealed significant gray matter volume reductions in the prefrontal and frontal cortices of MIA-treated offspring at 6 months that persisted through the final time point at 45 months along with smaller frontal white matter volumes in MIA-treated animals at 36 and 45 months. These findings provide the first evidence of early postnatal changes in brain development in MIA-exposed nonhuman primates and establish a translationally relevant model system to explore the neurodevelopmental trajectory of risk associated with prenatal immune challenge from birth through late adolescence.SIGNIFICANCE STATEMENT Women exposed to infection during pregnancy have an increased risk of giving birth to a child who will later be diagnosed with a neurodevelopmental disorder. Preclinical maternal immune activation (MIA) models have demonstrated that the effects of maternal infection on fetal brain development are mediated by maternal immune response. Since the majority of MIA models are conducted in rodents, the nonhuman primate provides a unique system to evaluate the MIA hypothesis in a species closely related to humans. Here we report the first longitudinal study conducted in a nonhuman primate MIA model. MIA-exposed offspring demonstrate subtle changes in cognitive development paired with marked reductions in frontal gray and white matter, further supporting the association between prenatal immune challenge and alterations in offspring neurodevelopment.

Subtle alterations in neonatal neurodevelopment following early or late exposure to prenatal maternal immune activation in mice

Prenatal exposure to maternal immune activation (MIA) is a risk factor for a variety of neurodevelopmental and psychiatric disorders. The timing of MIA-exposure has been shown to affect adolescent and adult offspring neurodevelopment, however, less is known about these effects in the neonatal period. To better understand the impact of MIA-exposure on neonatal brain development in a mouse model, we assess neonate communicative abilities with the ultrasonic vocalization task, followed by high-resolution ex vivo magnetic resonance imaging (MRI) on the neonatal (postnatal day 8) mouse brain. Early exposed offspring displayed decreased communicative ability, while brain anatomy appeared largely unaffected, apart from some subtle alterations. By integrating MRI and behavioural assays to investigate the effects of MIA-exposure on neonatal neurodevelopment we show that offspring neuroanatomy and behaviour are only subtly affected by both early and late exposure. This suggests that the deficits often observed in later stages of life may be dormant, not yet developed in the neonatal period, or not as easily detectable using a cross-sectional approach.

Early or Late Gestational Exposure to Maternal Immune Activation Alters Neurodevelopmental Trajectories in Mice: An Integrated Neuroimaging, Behavioral, and Transcriptional Study

BACKGROUND

Exposure to maternal immune activation (MIA) in utero is a risk factor for neurodevelopmental disorders later in life. The impact of the gestational timing of MIA exposure on downstream development remains unclear.

METHODS

We characterized neurodevelopmental trajectories of mice exposed to the viral mimetic poly I:C (polyinosinic:polycytidylic acid) either on gestational day 9 (early) or on day 17 (late) using longitudinal structural magnetic resonance imaging from weaning to adulthood. Using multivariate methods, we related neuroimaging and behavioral variables for the time of greatest alteration (adolescence/early adulthood) and identified regions for further investigation using RNA sequencing.

RESULTS

Early MIA exposure was associated with accelerated brain volume increases in adolescence/early adulthood that normalized in later adulthood in the striatum, hippocampus, and cingulate cortex. Similarly, alterations in anxiety-like, stereotypic, and sensorimotor gating behaviors observed in adolescence normalized in adulthood. MIA exposure in late gestation had less impact on anatomical and behavioral profiles. Multivariate maps associated anxiety-like, social, and sensorimotor gating deficits with volume of the dorsal and ventral hippocampus and anterior cingulate cortex, among others. The most transcriptional changes were observed in the dorsal hippocampus, with genes enriched for fibroblast growth factor regulation, autistic behaviors, inflammatory pathways, and microRNA regulation.

CONCLUSIONS

Leveraging an integrated hypothesis- and data-driven approach linking brain-behavior alterations to the transcriptome, we found that MIA timing differentially affects offspring development. Exposure in late gestation leads to subthreshold deficits, whereas exposure in early gestation perturbs brain development mechanisms implicated in neurodevelopmental disorders.

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.

Interrelationships Between Oxidative Stress, Cytokines, and Psychotic Symptoms and Executive Functions in Patients With Chronic Schizophrenia

OBJECTIVE

Accumulating evidence has demonstrated that the pathophysiology of schizophrenia is involved in various abnormalities in oxidative stress markers and cytokines closely related to synaptic plasticity. However, the interactive effects among key cytokines, oxidative stress, and executive dysfunction and symptoms of schizophrenia have not been investigated yet.

METHODS

A total of 189 patients with chronic schizophrenia and 60 controls were recruited in the current study. Tumor necrosis factor α (TNF-α), interleukin (IL)-8, IL-6, and IL-2 levels; catalase, glutathione peroxidase, and superoxide dismutase (SOD) activities; and malondialdehyde (MDA) levels were determined in patients and controls. Executive function was evaluated by the Wisconsin card sorting tests, the verbal fluency tests, and the Stroop word-color test. Clinical symptoms were evaluated by the Positive and Negative Syndrome Scale.

RESULTS

Relative to the controls, the patients had lower activities of SOD and glutathione peroxidase and levels of TNF-α, but higher levels of MDA, IL-8, IL-6, and IL-2 (all p values < .05). A significant negative relationship between SOD activity and IL-8 levels was found only in patients (β = -0.44, p = .008). Furthermore, we found that an interactive effect of low TNF-α level and high MDA level was associated with negative symptoms (β = -0.02, p = .01). Moreover, the interactive effects of IL-8 and MDA or IL-8 and SOD were correlated with executive function only in patients (β = 0.23, p = .02; β = 0.09, p = .03).

CONCLUSIONS

Our findings suggest that the interrelationships between oxidative stress markers and cytokines occur in schizophrenia patients, which may be the basis of their pathological mechanisms underlying clinical symptoms and cognitive dysfunction.

Microbiota and Microglia Interactions in ASD

Autism spectrum disorders (ASD) are serious, highly variable neurodevelopmental disorders, commonly characterized by the manifestation of specific behavioral abnormalities, such as stereotypic behaviors and deficits in social skills, including communication. Although the neurobiological basis for ASD has attracted attention in recent decades, the role of microglial cells, which are the main resident myeloid cell population in the brain, is still controversial and underexplored. Microglia play several fundamental roles in orchestrating brain development and homeostasis. As such, alterations in the intrinsic functions of these cells could be one of the driving forces responsible for the development of various neurodevelopmental disorders, including ASD. Microglia are highly sensitive to environmental cues. Amongst the environmental factors known to influence their intrinsic functions, the gut microbiota has emerged as a central player, controlling both microglial maturation and activation. Strikingly, there is now compelling data suggesting that the intestinal microbiota can play a causative role in driving the behavioural changes associated with ASD. Not only is intestinal dysbiosis commonly reported in ASD patients, but therapies targeting the microbiome can markedly alleviate behavioral symptoms. Here we explore the emerging mechanisms by which altered microglial functions could contribute to several major etiological factors of ASD. We then demonstrate how pre- and postnatal environmental stimuli can modulate microglial cell phenotype and function, underpinning the notion that reciprocal interactions between microglia and intestinal microbes could play a crucial role in ASD aetiology.

Immunoceptive inference: why are psychiatric disorders and immune responses intertwined?

There is a steadily growing literature on the role of the immune system in psychiatric disorders. So far, these advances have largely taken the form of correlations between specific aspects of inflammation (e.g. blood plasma levels of inflammatory markers, genetic mutations in immune pathways, viral or bacterial infection) with the development of neuropsychiatric conditions such as autism, bipolar disorder, schizophrenia and depression. A fundamental question remains open: why are psychiatric disorders and immune responses intertwined? To address this would require a step back from a historical mind-body dualism that has created such a dichotomy. We propose three contributions of active inference when addressing this question: translation, unification, and simulation. To illustrate these contributions, we consider the following questions. Is there an immunological analogue of sensory attenuation? Is there a common generative model that the brain and immune system jointly optimise? Can the immune response and psychiatric illness both be explained in terms of self-organising systems responding to threatening stimuli in their external environment, whether those stimuli happen to be pathogens, predators, or people? Does false inference at an immunological level alter the message passing at a psychological level (or vice versa) through a principled exchange between the two systems?

Using cortical non-invasive neuromodulation as a potential preventive treatment in schizophrenia - A review

BACKGROUND

Evidence suggests that schizophrenia constitutes a neurodevelopmental disorder, characterized by a gradual emergence of behavioral and neurobiological abnormalities over time. Therefore, applying early interventions to prevent later manifestation of symptoms is appealing.

OBJECTIVE

This review focuses on the use of cortical neuromodulation in schizophrenia and its potential as a preventive treatment approach. We present clinical and preclinical findings investigating the use of neuromodulation in schizophrenia, including the current research focusing on cortical non-invasive stimulation and its possibility as a future preventive treatment.

METHODS

We performed a search in Medline (PubMed) in September 2020 using a combination of relevant medical subject headings (MeSH) and text words. The search included human and preclinical trials as well as existing systematic reviews and meta-analysis. There were no restrictions on language or the date of publication.

RESULTS

Neurodevelopmental animal models may be used to investigate how the disease progresses and thus which brain areas ideally should be targeted at a given time point. Here, abnormalities of the prefrontal cortex have been often identified as an early and persistent impairment in schizophrenia. Currently there is insufficient evidence to either support or refute the use of neuromodulation to the cortex in adult patients with already manifested symptoms. However, preclinical results show that early non-invasive neuromodulation to the prefrontal cortex of adolescent animals, sufficiently prevents later psychosis-relevant abnormalities in adulthood. This points to the promising potential of cortical non-invasive neuromodulation as a preventive treatment when applied early in the course of the disease.

CONCLUSION

Preclinical translational-oriented findings indicate, that neuromodulation to cortical areas offers the possibility of targeting early neuropathology and through this diminish the progression of a later schizophrenic profile. Further studies are needed to investigate whether such early cortical stimulation may serve as a future preventive treatment in schizophrenia.

A profile and review of findings from the Early Markers for Autism study: unique contributions from a population-based case-control study in California

BACKGROUND

The Early Markers for Autism (EMA) study is a population-based case-control study designed to learn more about early biologic processes involved in ASD.

METHODS

Participants were drawn from Southern California births from 2000 to 2003 with archived prenatal and neonatal screening specimens. Across two phases, children with ASD (n = 629) and intellectual disability without ASD (ID, n = 230) were ascertained from the California Department of Developmental Services (DDS), with diagnoses confirmed according to DSM-IV-TR criteria based on expert clinical review of abstracted records. General population controls (GP, n = 599) were randomly sampled from birth certificate files and matched to ASD cases by sex, birth month and year after excluding individuals with DDS records. EMA has published over 20 papers examining immune markers, endogenous hormones, environmental chemicals, and genetic factors in association with ASD and ID. This review summarizes the results across these studies, as well as the EMA study design and future directions.

RESULTS

EMA enabled several key contributions to the literature, including the examination of biomarker levels in biospecimens prospectively collected during critical windows of neurodevelopment. Key findings from EMA include demonstration of elevated cytokine and chemokine levels in maternal mid-pregnancy serum samples in association with ASD, as well as aberrations in other immune marker levels; suggestions of increased odds of ASD with prenatal exposure to certain endocrine disrupting chemicals, though not in mixture analyses; and demonstration of maternal and fetal genetic influence on prenatal chemical, and maternal and neonatal immune marker and vitamin D levels. We also observed an overall lack of association with ASD and measured maternal and neonatal vitamin D, mercury, and brain-derived neurotrophic factor (BDNF) levels.

LIMITATIONS

Covariate and outcome data were limited to information in Vital Statistics and DDS records. As a study based in Southern California, generalizability for certain environmental exposures may be reduced.

CONCLUSIONS

Results across EMA studies support the importance of the prenatal and neonatal periods in ASD etiology, and provide evidence for the role of the maternal immune response during pregnancy. Future directions for EMA, and the field of ASD in general, include interrogation of mechanistic pathways and examination of combined effects of exposures.

Cord Serum Cytokines at Birth and Children's Anxiety-Depression Trajectories From 3 to 8 Years: The EDEN Mother-Child Cohort

BACKGROUND

Recent research suggests that immune dysregulation in pregnancy could be a risk factor for anxiety and depression symptoms in offspring. Whereas animal studies have demonstrated the importance of the link between perinatal cytokines and abnormal behaviors in offspring, human epidemiological studies in this area remain limited. The objectives of the study were to describe the network of cord serum cytokines at birth and test whether they are associated with subsequent anxiety and depression symptom trajectories in offspring.

METHODS

We used data and biological samples from 871 mother-child pairs followed up from pregnancy to 8 years of age and participating in the French mother-child cohort EDEN (a study on the pre- and early postnatal determinants of child health and development). Cord serum cytokines were measured at birth. Children's symptoms of anxiety and depression were assessed with the emotional difficulties subscore of the Strength and Difficulties Questionnaire at ages 3, 5, and 8 years, from which trajectories of anxiety-depression symptoms were derived.

RESULTS

Results showed a significant association between cord serum interleukin-7 at birth and the trajectories of children's anxiety-depression symptoms between ages 3 to 8 years (adjusted odds ratio, 0.73; 95% confidence interval, 0.57-0.93). The associations considered relevant confounders, including prenatal maternal depressive symptoms.

CONCLUSIONS

Early immune changes may contribute to subsequent anxiety and depression symptoms in childhood. Beyond the understanding of mechanisms underlying the occurrence of emotional difficulties in children, our findings open avenues for future research in human and animals.

Altered circadian rhythms in a mouse model of neurodevelopmental disorders based on prenatal maternal immune activation

Individuals with neurodevelopmental disorders, such as schizophrenia and autism spectrum disorder, exhibit various sleep and circadian rhythm disturbances that often persist and worsen throughout the lifespan. To study the interaction between circadian rhythm disruption and neurodevelopmental disorders, we utilized a mouse model based on prenatal maternal immune activation (MIA). We hypothesized that MIA exposure would lead to impaired circadian locomotor activity rhythms in adult mouse offspring. We induced MIA by injecting pregnant dams with polyinosinic:polycytidylic acid (poly IC) at embryonic day 9.5, then aged resulting offspring to adulthood. We first confirmed that poly IC injection in pregnant dams elevated plasma levels of pro- and anti-inflammatory cytokines and chemokines. We then placed adult offspring in running wheels and subjected them to various lighting conditions. Overall, poly IC-exposed male offspring exhibited altered locomotor activity rhythms, reminiscent of individuals with neurodevelopmental disorders. In particular, we report increased (subjective) day activity across 3 different lighting conditions: 12 h of light, 12 h of dark (12:12LD), constant darkness (DD) and constant light. Further data analysis indicated that this was driven by increased activity in the beginning of the (subjective) day in 12:12LD and DD, and at the end of the day in 12:12LD. This effect was sex-dependent, as in utero poly IC exposure led overall to much milder alterations in locomotor activity rhythms in female offspring than in male offspring. We also confirmed that the observed behavioral impairments in adult poly IC-exposed offspring were not due to differences in maternal behavior. These data further our understanding of the link between circadian rhythm disruption and neurodevelopmental disorders and may have implications for mitigating risk to the disorders and/or informing the development of circadian-based therapies.

Maternal dietary omega-3 deficiency worsens the deleterious effects of prenatal inflammation on the gut-brain axis in the offspring across lifetime

Maternal immune activation (MIA) and poor maternal nutritional habits are risk factors for the occurrence of neurodevelopmental disorders (NDD). Human studies show the deleterious impact of prenatal inflammation and low n-3 polyunsaturated fatty acid (PUFA) intake on neurodevelopment with long-lasting consequences on behavior. However, the mechanisms linking maternal nutritional status to MIA are still unclear, despite their relevance to the etiology of NDD. We demonstrate here that low maternal n-3 PUFA intake worsens MIA-induced early gut dysfunction, including modification of gut microbiota composition and higher local inflammatory reactivity. These deficits correlate with alterations of microglia-neuron crosstalk pathways and have long-lasting effects, both at transcriptional and behavioral levels. This work highlights the perinatal period as a critical time window, especially regarding the role of the gut-brain axis in neurodevelopment, elucidating the link between MIA, poor nutritional habits, and NDD.

Neurodevelopmental insights into circuit dysconnectivity in schizophrenia

Schizophrenia is increasingly being recognized as a disorder of brain circuits of developmental origin. Animal models, however, have been technically limited in exploring the effects of early developmental circuit abnormalities on the maturation of the brain and associated behavioural outputs. This review discusses evidence of the developmental emergence of circuit abnormalities in schizophrenia, followed by a critical assessment on how animal models need to be adapted through optimized tools in order to spatially and temporally manipulate early developmental events, thereby providing insight into the causal contribution of developmental perturbations to schizophrenia.

Association Between Epidural Analgesia During Labor and Risk of Autism Spectrum Disorders in Offspring

IMPORTANCE

Although the safety of labor epidural analgesia (LEA) for neonates has been well documented, the long-term health effects of LEA on offspring remain to be investigated.

OBJECTIVE

To assess the association between maternal LEA exposure and risk of autism spectrum disorders (ASDs) in offspring.

DESIGN, SETTING, AND PARTICIPANTS

Data for this retrospective longitudinal birth cohort study were derived from electronic medical records from a population-based clinical birth cohort. A total of 147 895 singleton children delivered vaginally between January 1, 2008, and December 31, 2015, in a single integrated health care system were included. Children were followed up from the age of 1 year until the first date of the following occurrences: clinical diagnosis of ASD, last date of health plan enrollment, death, or the study end date of December 31, 2018.

EXPOSURES

Use and duration of LEA.

MAIN OUTCOMES AND MEASURES

The main outcome was clinical diagnosis of ASD. Cox proportional hazards regression analysis was used to estimate the hazard ratio (HR) of ASD associated with LEA exposure.

RESULTS

Among the cohort of 147 895 singleton children (74 425 boys [50.3%]; mean [SD] gestational age at delivery, 38.9 [1.5] weeks), 109 719 (74.2%) were exposed to maternal LEA. Fever during labor was observed in 13 055 mothers (11.9%) in the LEA group and 510 of 38 176 mothers (1.3%) in the non-LEA group. Autism spectrum disorders were diagnosed in 2039 children (1.9%) in the LEA group and 485 children (1.3%) in the non-LEA group. After adjusting for potential confounders, including birth year, medical center, maternal age at delivery, parity, race/ethnicity, educational level, household income, history of comorbidity, diabetes during pregnancy, smoking during pregnancy, preeclampsia or eclampsia, prepregnancy body mass index, gestational weight gain, gestational age at delivery, and birth weight, the HR associated with LEA vs non-LEA exposure was 1.37 (95% CI, 1.23-1.53). Relative to the unexposed group, the adjusted HR associated with LEA exposure of less than 4 hours was 1.33 (95% CI, 1.17-1.53), with LEA exposure of 4 to 8 hours was 1.35 (95% CI, 1.20-1.53), and with LEA exposure of more than 8 hours was 1.46 (95% CI, 1.27-1.69). Within the LEA group, there was a significant trend of ASD risk associated with increasing duration of LEA exposure after adjusting for covariates (HR for linear trend, 1.05 [95% CI, 1.01-1.09] per 4 hours). Adding fever to the model did not change the HR estimate associated with LEA exposure (adjusted HR for LEA vs non-LEA, 1.37 [95% CI, 1.22-1.53]).

CONCLUSIONS AND RELEVANCE

This study suggests that maternal LEA may be associated with increased ASD risk in children. The risk appears to not be directly associated with epidural-related maternal fever.

Enduring neuroimmunological consequences of developmental experiences: From vulnerability to resilience

The immune system is crucial for normal neuronal development and function (neuroimmune system). Both immune and neuronal systems undergo significant postnatal development and are sensitive to developmental programming by environmental experiences. Negative experiences from infection to psychological stress at a range of different time points (in utero to adolescence) can permanently alter the function of the neuroimmune system: given its prominent role in normal brain development and function this dysregulation may increase vulnerability to psychiatric illness. In contrast, positive experiences such as exercise and environmental enrichment are protective and can promote resilience, even restoring the detrimental effects of negative experiences on the neuroimmune system. This suggests the neuroimmune system is a viable therapeutic target for treatment and prevention of psychiatric illnesses, especially those related to stress. In this review we will summarise the main cells, molecules and functions of the immune system in general and with specific reference to central nervous system development and function. We will then discuss the effects of negative and positive environmental experiences, especially during development, in programming the long-term functioning of the neuroimmune system. Finally, we will review the sparse but growing literature on sex differences in neuroimmune development and response to environmental experiences.

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The immune system is essential for development and function of the central nervous system (neuroimmune system)

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Environmental experiences can permanently alter neuroimmune function and associated brain development

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Altered neuroimmune function following negative developmental experiences may play a role in psychiatric illnesses

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Positive experiences can promote resilience and rescue the effects of negative experiences on the neuroimmune system

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The neuroimmune system is therefore a viable therapeutic target for preventing and treating psychiatric illnesses