Maternal immune activation in neurodevelopmental disorders

The roles of immune factors in neurodevelopment

The development of the nervous system is a highly complex process orchestrated by a multitude of factors, including various immune elements. These immune components play a dual role, not only regulating the immune response but also actively influencing brain development under both physiological and pathological conditions. The brain's immune barrier includes microglia in the brain parenchyma, which act as resident macrophages, astrocytes that support neuronal function and contribute to the inflammatory response, as well as circulating immune cells that reside at the brain's borders, including the choroid plexus, meninges, and perivascular spaces. Cytokines-soluble signaling molecules released by immune cells-play a crucial role in mediating communication between immune cells and the developing nervous system. Cytokines regulate processes such as neurogenesis, synaptic pruning, and inflammation, helping to shape the neural environment. Dysregulation of these immune cells, astrocytes, or cytokine signaling can lead to alterations in neurodevelopment, potentially contributing to neurodevelopmental abnormalities. This article reviews the central role of microglia, astrocytes, cytokines, and other immune factors in neurodevelopment, and explores how neuroinflammation can lead to the onset of neurodevelopmental disorders, shedding new light on their pathogenesis.

Peripheral Blood Monocytes as Biomarkers of Neurodevelopmental Disorders: A Systematic Review and Meta-Analysis

Accumulating evidence implicates immune dysregulation and chronic inflammation in neurodevelopmental disorders (NDDs), often manifesting as abnormal alterations in peripheral blood immune cell levels. The mononuclear phagocyte system, including monocytes and microglia, has been increasingly recognized for its involvement in the pathogenesis of NDDs. However, due to inconsistent findings in the literature, whether monocytes can serve as a reliable biomarker for NDDs remains controversial. To address this issue, we conducted a systematic review and meta-analysis of studies examining monocyte counts in NDD individuals. A comprehensive search was conducted across PubMed, Web of Science, and Scopus databases. Variables extracted for analysis encompassed the author's name, year of study, sample size, patient's age, type of disease, mean, standard deviation of monocytes and sex ratio. A total of 2503 articles were found by searching the three databases. After removed duplicates and screening titles, abstracts, and full texts, 17 articles met the inclusion criteria, and 20 independent studies were included in the meta-analysis. The results indicated significantly increased monocyte counts in 5 type NDDs compared to Typical Development (TD) groups (g = 0.36, 95%CI [0.23, 0.49]). Subgroup analyses revealed no significant differences in monocyte counts across different NDD types, gender, or age. These findings suggest that aberrant alterations in monocyte counts are common in NDD cases, indicating their potential as biomarkers for these conditions. Future research should further investigate the role of monocyte in understanding the mechanisms, early detection, and clinical diagnosis of NDDs.

Understanding the potential impact of trimester-specific maternal immune activation due to SARS-CoV-2 on early human neurodevelopment and the role of cytokine balance

Purpose

The COVID-19 pandemic presents significant future health challenges. Its impact on pregnant women and their newborn is a particular area of concern. This study aims to examine the potential role of maternal immune activation (MIA), due to SARS-CoV-2 infection, on early neurodevelopment.

Methods

We analysed 107 mother-infant dyads from the COGESTCOV-19 study in Cantabria, Spain, which included 59 SARS-CoV-2 exposed (cases) and 48 unexposed (controls) mothers, recruited between December 2020 and February 2022. Cytokine levels (IL-6 and IL-10) were obtained from maternal blood and cord blood. Neurodevelopment was assessed using the Neonatal Behavioral Assessment Scale (NBAS) at six weeks of age. Trimester of infection was considered in the main analyses.

Results

Results showed no significant overall delays in early neurodevelopment due to maternal SARS-CoV-2 infection. Control infants performed better in some NBAS items. However, cases infants showed trimester-specific differences. First-trimester exposure was related to motor and reflex delays, second-trimester to poorer performances in motor tasks and autonomic stability, and third-trimester to weaker state organization, regulation, and reflexes. Some correlations between cytokine levels and NBAS performance showed moderate associations.

Conclusions

These findings highlight the need for ongoing neurodevelopmental monitoring of infants born during the COVID-19 pandemic. The study enhances our understanding of MIA's impact on early development, emphasizing the importance of addressing homeostatic mechanisms in mothers and newborns.

A pathway-based genetic score for inflammation: An indicator of vulnerability to phthalate-induced adverse neurodevelopment outcomes

INTRODUCTION

Phthalates, chemical additives used to enhance plastic products' flexibility, are easily released into the environment, and can harm the brain development through various mechanisms including inflammation. Genetic variation influencing an individual's susceptibility to inflammation may play a role in the effects of phthalate exposure on neurodevelopment however there is no summary measure developed for genetic susceptibility to inflammation.

METHODS

We developed a genetic pathway function score for inflammation (gPFSin), based on the transcriptional activity of the inflammatory response pathway in the brain and other tissues. Using the Barwon Infant Study (a birth cohort of n = 1074), we examined the connection between gPFSin and key neurodevelopmental outcomes, along with the interplay between prenatal phthalate levels, children's genetic susceptibility to inflammation (gPFSin), and adverse neurodevelopmental outcomes.

RESULTS

Regression techniques revealed consistent associations between gPFSin-phthalate combinations and key neurodevelopmental outcomes. A high gPFSin score was associated with an increased risk of doctor-diagnosed Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) by age 11.5 years, with adjusted odds ratios of 2.15(p = 0.039) and 2.42(p = 0.005), respectively. Furthermore, individuals with both high gPFSin and prenatal phthalate exposure exhibited more neurodevelopmental problems. This included associations of high gPFSin and bis(2-ethylhexyl) phthalate (DEHP) levels with parent-reported ASD traits and doctor-diagnosed ASD. The attributable proportions due to this interaction were 0.39 (p = 0.045) and 0.37 (p = 0.037), respectively.

CONCLUSION

These findings contribute to the evidence linking gestational phthalate exposure and inflammation to adverse neurodevelopment and underscoring increased risks in children with higher genetic susceptibility to inflammation.

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.

Potential key pathophysiological participant and treatment target in autism spectrum disorder: Microglia

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by social and communication deficits, as well as restricted or repetitive behaviors or interests. Although the etiology of ASD remains unclear, there is abundant evidence suggesting that microglial dysfunction is likely to be a significant factor in the pathophysiology of ASD. Microglia, the primary innate immune cells in the central nervous system (CNS), play a crucial role in brain development and homeostasis. Recently, numerous studies have shown that microglia in ASD models display various abnormalities including morphology, function, cellular interactions, genetic and epigenetic factors, as well as the expression of receptors, transcription factors, and cytokines. They impact normal neural development through various mechanisms contributing to ASD, such as neuroinflammation, and alterations in synaptic formation and pruning. The focus of this review is on recent studies regarding microglial abnormalities in ASD and their effects on the onset and progression of ASD at both cellular and molecular levels. It can provide insight into the specific contribution of microglia to ASD pathogenesis and help in designing potential therapeutic and preventative strategies targeting microglia.

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.

Gestational administration of Bifidobacterium dentium results in intergenerational modulation of inflammatory, metabolic, and social behavior

Prenatal stress (PNS) profoundly impacts maternal and offspring health, with enduring effects including microbiome alterations, neuroinflammation, and behavioral disturbances such as reductions in social behavior. Converging lines of evidence from preclinical and clinical studies suggest that PNS disrupts tryptophan (Trp) metabolic pathways and reduces gut Bifidobacteria, a known beneficial bacterial genus that metabolizes Trp. Specifically, previous work from our lab demonstrated that human prenatal mood disorders in mothers are associated with reduced Bifidobacterium dentium in infants at 13 months. Given that Bifidobacterium has been positively associated with neurodevelopmental and other health benefits and is depleted by PNS, we hypothesized that supplementing PNS-exposed pregnant dams with B. dentium would ameliorate PNS-induced health deficits. We measured inflammatory outputs, Trp metabolite levels and enzymatic gene expression in dams and fetal offspring, and social behavior in adult offspring. We determined that B. dentium reduced maternal systemic inflammation and fetal offspring neuroinflammation, while modulating tryptophan metabolism and increasing kynurenic acid and indole-3-propionic acid intergenerationally. Additional health benefits were demonstrated by the abrogation of PNS-induced reductions in litter weight. Finally, offspring of the B. dentium cohort demonstrated increased sociability in males primarily and increased social novelty primarily in females. Together these data illustrate that B. dentium can orchestrate interrelated host immune, metabolic and behavioral outcomes during and after gestation for both dam and offspring and may be a candidate for prevention of the negative sequelae of stress.

Synaptic proteome perturbations after maternal immune activation: Identification of embryonic and adult hippocampal changes

BACKGROUND

Maternal immune activation (MIA) triggers neurobiological changes in offspring, potentially reshaping the molecular synaptic landscape, with the hippocampus being particularly vulnerable. However, critical details regarding developmental timing of these changes and whether they differ between males and females remain unclear.

METHODS

We induced MIA in C57BL/6J mice on gestational day nine using the viral mimetic poly(I:C) and performed mass spectrometry-based proteomic analyses on hippocampal synaptoneurosomes of embryonic (E18) and adult (20 ± 1 weeks) MIA offspring.

RESULTS

In the embryonic synaptoneurosomes, MIA led to lipid, polysaccharide, and glycoprotein metabolism pathway disruptions. In the adult synaptic proteome, we observed a dynamic shift toward transmembrane trafficking, intracellular signalling cascades, including cell death and growth, and cytoskeletal organisation. In adults, many associated pathways overlapped between males and females. However, we found distinct sex-specific enrichment of dopaminergic and glutamatergic pathways. We identified 50 proteins altered by MIA in both embryonic and adult samples (28 with the same directionality), mainly involved in presynaptic structure and synaptic vesicle function. We probed human phenome-wide association study data in the cognitive and psychiatric domains, and 49 of the 50 genes encoding these proteins were significantly associated with the investigated phenotypes.

CONCLUSIONS

Our data emphasise the dynamic effects of viral-like MIA on developing and mature hippocampi and provide novel targets for study following prenatal immune challenges. The 22 proteins that changed directionality from the embryonic to adult hippocampus, suggestive of compensatory over-adaptions, are particularly attractive for future investigations.

Risk of Neurodevelopmental Disorders in Offspring of Parents with Major Depressive Disorder: A Birth Cohort Study

Studies have reported inconsistent results regarding associations between parental depression and offspring neurodevelopmental disorders, such as developmental delay and autism spectrum disorder (ASD). In all, 7,593 children who were born between 1996 and 2010 in Taiwan and had at least one parent with major depressive disorder and 75,930 birth-year- and sex-matched children of parents without major depressive disorder were followed from 1996 or time of birth to the end of 2011. Intergroup differences in neurodevelopmental conditions-including ASD, attention-deficit hyperactivity disorder (ADHD), tic disorder, developmental delay, and intellectual disability (ID)-were assessed. Compared with the children in the control group, the children of parents with major depression were more likely [hazard ratio (HR), 95% confidence interval (CI)] to develop ADHD (1.98, 1.80-2.18), ASD (1.52, 1.16-1.94), tic disorder (1.40, 1.08-1.81), developmental delay (1.32, 1.20-1.45), and ID (1.26, 1.02-1.55). Parental depression was associated with offspring neurodevelopmental disorders, specifically ASD, ADHD, developmental delay, ID, and tic disorder. Therefore, clinicians should closely monitor the neurodevelopmental conditions of children of parents with depression.

Mesenchymal Stem Cells and Purinergic Signaling in Autism Spectrum Disorder: Bridging the Gap between Cell-Based Strategies and Neuro-Immune Modulation

The prevalence of autism spectrum disorder (ASD) is still increasing, which means that this neurodevelopmental lifelong pathology requires special scientific attention and efforts focused on developing novel therapeutic approaches. It has become increasingly evident that neuroinflammation and dysregulation of neuro-immune cross-talk are specific hallmarks of ASD, offering the possibility to treat these disorders by factors modulating neuro-immunological interactions. Mesenchymal stem cell-based therapy has already been postulated as one of the therapeutic approaches for ASD; however, less is known about the molecular mechanisms of stem cell influence. One of the possibilities, although still underestimated, is the paracrine purinergic activity of MSCs, by which stem cells ameliorate inflammatory reactions. Modulation of adenosine signaling may help restore neurotransmitter balance, reduce neuroinflammation, and improve overall brain function in individuals with ASD. In our review article, we present a novel insight into purinergic signaling, including but not limited to the adenosinergic pathway and its role in neuroinflammation and neuro-immune cross-talk modulation. We anticipate that by achieving a greater understanding of the purinergic signaling contribution to ASD and related disorders, novel therapeutic strategies may be devised for patients with autism in the near future.

GABA system as the cause and effect in early development

GABA is the primary inhibitory neurotransmitter in the adult brain and through its actions on GABAARs, it protects against excitotoxicity and seizure activity, ensures temporal fidelity of neurotransmission, and regulates concerted rhythmic activity of neuronal populations. In the developing brain, the development of GABAergic neurons precedes that of glutamatergic neurons and the GABA system serves as a guide and framework for the development of other brain systems. Despite this early start, the maturation of the GABA system also continues well into the early postnatal period. In this review, we organize evidence around two scenarios based on the essential and protracted nature of GABA system development: 1) disruptions in the development of the GABA system can lead to large scale disruptions in other developmental processes (i.e., GABA as the cause), 2) protracted maturation of this system makes it vulnerable to the effects of developmental insults (i.e., GABA as the effect). While ample evidence supports the importance of GABA/GABAAR system in both scenarios, large gaps in existing knowledge prevent strong mechanistic conclusions.

Neurodevelopmental delay in children exposed to maternal SARS-CoV-2 in-utero

It is unclear if SARS CoV-2 infection during pregnancy is associated with adverse neurodevelopmental repercussions to infants. We assessed pediatric neurodevelopmental outcomes in children born to mothers with laboratory-confirmed SARS CoV-2 infection during pregnancy. Neurodevelopmental outcomes of in-utero exposed children were compared to that of pre-pandemic control children in Los Angeles (LA), CA, USA and Rio de Janeiro, Brazil. Bayley Scales of Infant and Toddler Development, 3rd edition (Bayley-III), the gold standard tool for evaluating neurodevelopment until 36 months of age and Ages and Stages Questionnaires (ASQ-3), a frequently used screening instrument for evaluating neurodevelopment in this same age group were the assessment tools used. Developmental delay (DD) was defined as having a score < - 2 SD below the norm (< 70) in at least one of three Bayley-III domains, (cognitive, motor or language) or a score below the cut-off (dark zone) in at least one of five ASQ-3 domains (communication, gross motor, fine motor, problem solving, personal-social). Exposed children were born between April 2020 and December 2022 while control children were born between January 2016 to December 2019. Neurodevelopmental testing was performed in 300 children total: 172 COVID-19 exposed children between 5-30 months of age and 128 control children between 6-38 months of age. Bayley-III results demonstrated that 12 of 128 exposed children (9.4%) had DD versus 2 of 128 controls (1.6%), p = 0.0007. Eight of 44 additional exposed children had DD on ASQ-3 testing. Fully, 20 of 172 exposed children (11.6%) and 2 of 128 control children (1.6%), p = 0.0006 had DD. In Rio, 12% of exposed children versus 2.6% of controls, p = 0.02 had DD. In LA, 5.7% of exposed children versus 0 controls, p = 0.12 had DD. Severe/critical maternal COVID-19 predicted below average neurodevelopment in the exposed cohort (OR 2.6, 95% CI 1.1-6.4). Children exposed to antenatal COVID-19 have a tenfold higher frequency of DD as compared to controls and should be offered neurodevelopmental follow-up.

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.

Maternal immune activation induces sex-dependent behavioral differences in a rat model of schizophrenia

Background

Maternal immune activation (MIA) is a mature means to construct a schizophrenia model. However, some preclinical studies have reported that a MIA-induced schizophrenia model seemed to have gender heterogeneity in behavioral phenotype. On the other hand, the MIA's paradigms were diverse in different studies, and many details could affect the effect of MIA. To some extent, it is not credible and scientific to directly compare the gender differences of different MIA programs. Therefore, it is necessary to study whether the sex of the exposed offspring leads to behavioral differences on the premise of maintaining a consistent MIA mode.

Methods

An animal model of schizophrenia was established by the administration of 10 mg/kg Poly (I: C) when dams were on day 9 of gestation. Then, a number of female and male offspring completed a series of behavioral tests during postnatal days 61-75.

Results

Compared with the female control group (n = 14), female MIA offspring (n = 12) showed a longer movement distance (d = 1.07, p < 0.05) and higher average speed (d = 1.08, p < 0.05) in the open field test (OFT). In the Y maze test, the percentage of entering the novel arm of female MIA offspring was lower (d = 0.92, p < 0.05). Compared with the male control group (n = 14), male MIA offspring (n = 13) displayed less movement distance (d = 0.93, p < 0.05) and a lower average speed (d = 0.94, p < 0.05) in the OFT. In the Y maze test, the proportion of exploration time in the novel arm of male MIA offspring was lower (d = 0.96, p < 0.05). In the EPM, male MIA offspring showed less time (d = 0.85, p < 0.05) and a lower percentage of time spent in the open arms (d = 0.85, p < 0.05). Male MIA offspring also had a lower PPI index (76 dB + 120 dB, d = 0.81, p < 0.05; 80 dB + 120 dB, d = 1.45, p < 0.01).

Conclusions

Our results showed that the behavioral phenotypes induced by prenatal immune activation were highly dependent on the sex of the offspring.

Maternal quercetin supplementation improved lipopolysaccharide-induced cognitive deficits and inflammatory response in a rat model of maternal immune activation

BACKGROUND

There is strong evidence that prenatal infection during a specific period of brain development increases the risk of neurodevelopmental disorders, partly through immune-inflammatory pathways. This suggests that anti-inflammatory agents could prevent these disorders by targeting the maternal inflammatory response. In the present study, we used a rat model of maternal immune activation (MIA) to examine whether maternal quercetin (QE) supplementation can alleviate behavioral deficits and inflammatory mediators in the prefrontal cortex (PFC) and hippocampus of adult male offspring.

METHODS

Pregnant rats were supplemented with QE (50 mg/kg) or vehicle throughout pregnancy and injected with either lipopolysaccharide (0.5 mg/kg) or saline on gestational days 15/16. At postnatal day 60, we evaluated the offspring's behavior, hippocampal and prefrontal cortex glial density, pro-inflammatory gene expression, and neuronal survival.

RESULTS

Our data showed that maternal QE supplementation can prevent working and recognition memory impairments in adult MIA offspring. This behavioral improvement correlates with the decrease in MIA-induced expression of pro-inflammatory genes, microglia, and astrocyte densities, without affecting neuronal survival, in both PFC and CA1 hippocampus areas.

CONCLUSION

Therefore, our study supports the potential preventive effect of QE on MIA-induced behavioral dysfunctions, at least in part, by suppressing the glial-mediated inflammatory response.

Inflammatory Conditions During Pregnancy and Risk of Autism and Other Neurodevelopmental Disorders

Background

Maternal inflammation can result from immune dysregulation and metabolic perturbations during pregnancy. Whether conditions associated with inflammation during pregnancy increase the likelihood of autism spectrum disorder (ASD) or other neurodevelopmental disorders (DDs) is not well understood.

Methods

We conducted a case-control study among children born in California from 2011 to 2016 to investigate maternal immune-mediated and cardiometabolic conditions during pregnancy and risk of ASD (n = 311) and DDs (n = 1291) compared with children from the general population (n = 967). Data on maternal conditions and covariates were retrieved from electronic health records. Maternal genetic data were used to assess a causal relationship.

Results

Using multivariable logistic regression, we found that mothers with asthma were more likely to deliver infants later diagnosed with ASD (odds ratio [OR] = 1.62, 95% CI: 1.15-2.29) or DDs (OR = 1.30, 95% CI: 1.02-1.64). Maternal obesity was also associated with child ASD (OR = 1.51, 95% CI: 1.07-2.13). Mothers with both asthma and extreme obesity had the greatest odds of delivering an infant later diagnosed with ASD (OR = 16.9, 95% CI: 5.13-55.71). These increased ASD odds were observed among female children only. Polygenic risk scores for obesity, asthma, and their combination showed no association with ASD risk. Mendelian randomization did not support a causal relationship between maternal conditions and ASD.

Conclusions

Inflammatory conditions during pregnancy are associated with risk for neurodevelopmental disorders in children. These risks do not seem to be due to shared genetic risk; rather, inflammatory conditions may share nongenetic risk factors with neurodevelopmental disorders. Children whose mothers have both asthma and obesity during pregnancy may benefit from earlier screening and intervention.

The impact of maternal immune activation on GABAergic interneuron development: A systematic review of rodent studies and their translational implications

Mothers exposed to infections during pregnancy disproportionally birth children who develop autism and schizophrenia, disorders associated with altered GABAergic function. The maternal immune activation (MIA) model recapitulates this risk factor, with many studies also reporting disruptions to GABAergic interneuron expression, protein, cellular density and function. However, it is unclear if there are species, sex, age, region, or GABAergic subtype specific vulnerabilities to MIA. Furthermore, to fully comprehend the impact of MIA on the GABAergic system a synthesised account of molecular, cellular, electrophysiological and behavioural findings was required. To this end we conducted a systematic review of GABAergic interneuron changes in the MIA model, focusing on the prefrontal cortex and hippocampus. We reviewed 102 articles that revealed robust changes in a number of GABAergic markers that present as gestationally-specific, region-specific and sometimes sex-specific. Disruptions to GABAergic markers coincided with distinct behavioural phenotypes, including memory, sensorimotor gating, anxiety, and sociability. Findings suggest the MIA model is a valid tool for testing novel therapeutics designed to recover GABAergic function and associated behaviour.

(R)-ketamine attenuates neurodevelopmental disease-related phenotypes in a mouse model of maternal immune activation

Infections during pregnancy are associated with an increased risk of neuropsychiatric disorders with developmental etiologies, such as schizophrenia and autism spectrum disorders (ASD). Studies have shown that the animal model of maternal immune activation (MIA) reproduces a wide range of phenotypes relevant to the study of neurodevelopmental disorders. Emerging evidence shows that (R)-ketamine attenuates behavioral, cellular, and molecular changes observed in animal models of neuropsychiatric disorders. Here, we investigate whether (R)-ketamine administration during adolescence attenuates some of the phenotypes related to neurodevelopmental disorders in an animal model of MIA. For MIA, pregnant Swiss mice received intraperitoneally (i.p.) lipopolysaccharide (LPS; 100 µg/kg/day) or saline on gestational days 15 and 16. The two MIA-based groups of male offspring received (R)-ketamine (20 mg/kg/day; i.p.) or saline from postnatal day (PND) 36 to 50. At PND 62, the animals were examined for anxiety-like behavior and locomotor activity in the open-field test (OFT), as well as in the social interaction test (SIT). At PND 63, the prefrontal cortex (PFC) was collected for analysis of oxidative balance and gene expression of the cytokines IL-1β, IL-6, and TGF-β1. We show that (R)-ketamine abolishes anxiety-related behavior and social interaction deficits induced by MIA. Additionally, (R)-ketamine attenuated the increase in lipid peroxidation and the cytokines in the PFC of the offspring exposed to MIA. The present work suggests that (R)-ketamine administration may have a long-lasting attenuation in deficits in emotional behavior induced by MIA, and that these effects may be attributed to its antioxidant and anti-inflammatory activity in the PFC.

The Ferritin, Hepcidin and Cytokines Link in the Diagnoses of Iron Deficiency Anaemia during Pregnancy: A Review

Following a diagnosis of iron deficiency anaemia in pregnancy, iron supplements are prescribed using UK guidelines; however, despite this, the condition remains highly prevalent, affecting up to 30% of pregnant women in the UK. According to the World Health Organisation, it globally accounts for 45% in the most vulnerable groups of pregnant women and infants (<5 years old). Recently, the efficacy of iron replacement therapy and the effectiveness of current standard testing of iron parameters have been reviewed in order to evaluate whether a more accurate diagnosis can be made using alternative and/or supplementary markers. Furthermore, many questions remain about the mechanisms involved in iron metabolism during pregnancy. The most recent studies have shed more light on serum hepcidin and raised questions on the significance of pregnancy related inflammatory markers including cytokines in iron deficiency anaemia. However, research into this is still scarce, and this review aims to contribute to further understanding and elucidating these areas.

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.

Maternal Chronic Ultrasound Stress Provokes Immune Activation and Behavioral Deficits in the Offspring: A Mouse Model of Neurodevelopmental Pathology

Neurodevelopmental disorders stemming from maternal immune activation can significantly affect a child's life. A major limitation in pre-clinical studies is the scarcity of valid animal models that accurately mimic these challenges. Among the available models, administration of lipopolysaccharide (LPS) to pregnant females is a widely used paradigm. Previous studies have reported that a model of 'emotional stress', involving chronic exposure of rodents to ultrasonic frequencies, induces neuroinflammation, aberrant neuroplasticity, and behavioral deficits. In this study, we explored whether this model is a suitable paradigm for maternal stress and promotes neurodevelopmental abnormalities in the offspring of stressed females. Pregnant dams were exposed to ultrasound stress for 21 days. A separate group was injected with LPS on embryonic days E11.5 and E12.5 to mimic prenatal infection. The behavior of the dams and their female offspring was assessed using the sucrose test, open field test, and elevated plus maze. Additionally, the three-chamber sociability test and Barnes maze were used in the offspring groups. ELISA and qPCR were used to examine pro-inflammatory changes in the blood and hippocampus of adult females. Ultrasound-exposed adult females developed a depressive-like syndrome, hippocampal overexpression of GSK-3β, IL-1β, and IL-6 and increased serum concentrations of IL-1β, IL-6, IL-17, RANTES, and TNFα. The female offspring also displayed depressive-like behavior, as well as cognitive deficits. These abnormalities were comparable to the behavioral changes induced by LPS. The ultrasound stress model can be a promising animal paradigm of neurodevelopmental pathology associated with prenatal 'emotional stress'.

Changes in cytokine and cytokine receptor levels during postnatal development of the human dorsolateral prefrontal cortex

In addition to their traditional roles in immune cell communication, cytokines regulate brain development. Cytokines are known to influence neural cell generation, differentiation, maturation, and survival. However, most work on the role of cytokines in brain development investigates rodents or focuses on prenatal events. Here, we investigate how mRNA and protein levels of key cytokines and cytokine receptors change during postnatal development of the human prefrontal cortex. We find that most cytokine transcripts investigated (IL1B, IL18, IL6, TNF, IL13) are lowest at birth and increase between 1.5 and 5 years old. After 5 years old, transcriptional patterns proceeded in one of two directions: decreased expression in teens and young adults (IL1B, p = 0.002; and IL18, p = 0.004) or increased mean expression with maturation, particularly in teenagers (IL6, p = 0.004; TNF, p = 0.002; IL13, p < 0.001). In contrast, cytokine proteins tended to remain elevated after peaking significantly around 3 years of age (IL1B, p = 0.012; IL18, p = 0.026; IL6, p = 0.039; TNF, p < 0.001), with TNF protein being highest in teenagers. An mRNA-only analysis of cytokine receptor transcripts found that early developmental increases in cytokines were paralleled by increases in their ligand-binding receptor subunits, such as IL1R1 (p = 0.033) and IL6R (p < 0.001) transcripts. In contrast, cytokine receptor-associated signaling subunits, IL1RAP and IL6ST, did not change significantly between age groups. Of the two TNF receptors, the 'pro-death' TNFRSF1A and 'pro-survival' TNFRSF1B, only TNFRSF1B was significantly changed (p = 0.028), increasing first in toddlers and again in young adults. Finally, the cytokine inhibitor, IL13, was elevated first in toddlers (p = 0.006) and again in young adults (p = 0.053). While the mean expression of interleukin-1 receptor antagonist (IL1RN) was highest in toddlers, this increase was not statistically significant. The fluctuations in cytokine expression reported here support a role for increases in specific cytokines at two different stages of human cortical development. The first is during the toddler/preschool period (IL1B, IL18, and IL13), and the other occurs at adolescence/young adult maturation (IL6, TNF and IL13).

Maternal immune activation and role of placenta in the prenatal programming of neurodevelopmental disorders

Maternal infection during pregnancy, leading to maternal immune activation (mIA) and cytokine release, increases the offspring risk of developing a variety of neurodevelopmental disorders (NDDs), including schizophrenia. Animal models have provided evidence to support these mechanistic links, with placental inflammatory responses and dysregulation of placental function implicated. This leads to changes in fetal brain cytokine balance and altered epigenetic regulation of key neurodevelopmental pathways. The prenatal timing of such mIA-evoked changes, and the accompanying fetal developmental responses to an altered in utero environment, will determine the scope of the impacts on neurodevelopmental processes. Such dysregulation can impart enduring neuropathological changes, which manifest subsequently in the postnatal period as altered neurodevelopmental behaviours in the offspring. Hence, elucidation of the functional changes that occur at the molecular level in the placenta is vital in improving our understanding of the mechanisms that underlie the pathogenesis of NDDs. This has notable relevance to the recent COVID-19 pandemic, where inflammatory responses in the placenta to SARS-CoV-2 infection during pregnancy and NDDs in early childhood have been reported. This review presents an integrated overview of these collective topics and describes the possible contribution of prenatal programming through placental effects as an underlying mechanism that links to NDD risk, underpinned by altered epigenetic regulation of neurodevelopmental pathways.

Neural crest E-cadherin loss drives cleft lip/palate by epigenetic modulation via pro-inflammatory gene-environment interaction

Gene-environment interactions are believed to play a role in multifactorial phenotypes, although poorly described mechanistically. Cleft lip/palate (CLP), the most common craniofacial malformation, has been associated with both genetic and environmental factors, with little gene-environment interaction experimentally demonstrated. Here, we study CLP families harbouring CDH1/E-Cadherin variants with incomplete penetrance and we explore the association of pro-inflammatory conditions to CLP. By studying neural crest (NC) from mouse, Xenopus and humans, we show that CLP can be explained by a 2-hit model, where NC migration is impaired by a combination of genetic (CDH1 loss-of-function) and environmental (pro-inflammatory activation) factors, leading to CLP. Finally, using in vivo targeted methylation assays, we demonstrate that CDH1 hypermethylation is the major target of the pro-inflammatory response, and a direct regulator of E-cadherin levels and NC migration. These results unveil a gene-environment interaction during craniofacial development and provide a 2-hit mechanism to explain cleft lip/palate aetiology.

Altered Purinergic Signaling in Neurodevelopmental Disorders: Focus on P2 Receptors

With the umbrella term 'neurodevelopmental disorders' (NDDs) we refer to a plethora of congenital pathological conditions generally connected with cognitive, social behavior, and sensory/motor alterations. Among the possible causes, gestational and perinatal insults have been demonstrated to interfere with the physiological processes necessary for the proper development of fetal brain cytoarchitecture and functionality. In recent years, several genetic disorders caused by mutations in key enzymes involved in purine metabolism have been associated with autism-like behavioral outcomes. Further analysis revealed dysregulated purine and pyrimidine levels in the biofluids of subjects with other NDDs. Moreover, the pharmacological blockade of specific purinergic pathways reversed the cognitive and behavioral defects caused by maternal immune activation, a validated and now extensively used rodent model for NDDs. Furthermore, Fragile X and Rett syndrome transgenic animal models as well as models of premature birth, have been successfully utilized to investigate purinergic signaling as a potential pharmacological target for these diseases. In this review, we examine results on the role of the P2 receptor signaling in the etiopathogenesis of NDDs. On this basis, we discuss how this evidence could be exploited to develop more receptor-specific ligands for future therapeutic interventions and novel prognostic markers for the early detection of these conditions.

P2 receptor-mediated signaling in the physiological and pathological brain: From development to aging and disease

The purinergic pathway mediates both pro-inflammatory and anti-inflammatory responses, whereas the breakdown of adenosine triphosphate (ATP) is in a critical equilibrium. Under physiological conditions, extracellular ATP is maintained at a nanomolar concentration. Whether released into the medium following tissue damage, inflammation, or hypoxia, ATP is considered a clear indicator of cell damage and a marker of pathological conditions. In this overview, we provide an update on the participation of P2 receptor-mediated purinergic signaling in normal and pathological brain development, with special emphasis on neurodevelopmental psychiatric disorders. Since purinergic signaling is ubiquitous, it is not surprising that it plays a prominent role in developmental processes and pathological alterations. The main aim of this review is to conceptualize the time-dependent dynamic changes in the participation of different players in the purinome in shaping the normal and aberrant developmental patterns and diseases of the central nervous system over one's lifespan.

Maternal Inflammation with Elevated Kynurenine Metabolites Is Related to the Risk of Abnormal Brain Development and Behavioral Changes in Autism Spectrum Disorder

Several studies show that genetic and environmental factors contribute to the onset and progression of neurodevelopmental disorders. Maternal immune activation (MIA) during gestation is considered one of the major environmental factors driving this process. The kynurenine pathway (KP) is a major route of the essential amino acid L-tryptophan (Trp) catabolism in mammalian cells. Activation of the KP following neuro-inflammation can generate various endogenous neuroactive metabolites that may impact brain functions and behaviors. Additionally, neurotoxic metabolites and excitotoxicity cause long-term changes in the trophic support, glutamatergic system, and synaptic function following KP activation. Therefore, investigating the role of KP metabolites during neurodevelopment will likely promote further understanding of additional pathophysiology of neurodevelopmental disorders, including autism spectrum disorder (ASD). In this review, we describe the changes in KP metabolism in the brain during pregnancy and represent how maternal inflammation and genetic factors influence the KP during development. We overview the patients with ASD clinical data and animal models designed to verify the role of perinatal KP elevation in long-lasting biochemical, neuropathological, and behavioral deficits later in life. Our review will help shed light on new therapeutic strategies and interventions targeting the KP for neurodevelopmental disorders.

Sex and gender in neurodevelopmental conditions

Health-related conditions often differ qualitatively or quantitatively between individuals of different birth-assigned sexes and gender identities, and/or with different gendered experiences, requiring tailored care. Studying the moderating and mediating effects of sex-related and gender-related factors on impairment, disability, wellbeing and health is of paramount importance especially for neurodivergent individuals, who are diagnosed with neurodevelopmental conditions with uneven sex/gender distributions. Researchers have become aware of the myriad influences that sex-related and gender-related variables have on the manifestations of neurodevelopmental conditions, and contemporary work has begun to investigate the mechanisms through which these effects are mediated. Here we describe topical concepts of sex and gender science, summarize current knowledge, and discuss research and clinical challenges related to autism, attention-deficit/hyperactivity disorder and other neurodevelopmental conditions. We consider sex and gender in the context of epidemiology, behavioural phenotypes, neurobiology, genetics, endocrinology and neighbouring disciplines. The available evidence supports the view that sex and gender are important contributors to the biological and behavioural variability in neurodevelopmental conditions. Methodological caveats such as frequent conflation of sex and gender constructs, inappropriate measurement of these constructs and under-representation of specific demographic groups (for example, female and gender minority individuals and people with intellectual disabilities) limit the translational potential of research so far. Future research and clinical implementation should integrate sex and gender into next-generation diagnostics, mechanistic investigations and support practices.

Haemorrhage of human foetal cortex associated with SARS-CoV-2 infection

Maternal viral infection and immune response are known to increase the risk of altered development of the foetal brain. Given the ongoing global pandemic of coronavirus disease 2019 (COVID-19), investigating the impact of SARS-CoV-2 on foetal brain health is of critical importance. Here, we report the presence of SARS-CoV-2 in first and second trimester foetal brain tissue in association with cortical haemorrhages. SARS-CoV-2 spike protein was sparsely detected within progenitors and neurons of the cortex itself, but was abundant in the choroid plexus of haemorrhagic samples. SARS-CoV-2 was also sparsely detected in placenta, amnion and umbilical cord tissues. Cortical haemorrhages were linked to a reduction in blood vessel integrity and an increase in immune cell infiltration into the foetal brain. Our findings indicate that SARS-CoV-2 infection may affect the foetal brain during early gestation and highlight the need for further study of its impact on subsequent neurological development.

Dual Role of the P2X7 Receptor in Dendritic Outgrowth during Physiological and Pathological Brain Development

At high levels, extracellular ATP operates as a "danger" molecule under pathologic conditions through purinergic receptors, including the ionotropic P2X7 receptor (P2X7R). Its endogenous activation is associated with neurodevelopmental disorders; however, its function during early embryonic stages remains largely unclear. Our objective was to determine the role of P2X7R in the regulation of neuronal outgrowth. For this purpose, we performed Sholl analysis of dendritic branches on primary hippocampal neurons and in acute hippocampal slices from WT mice and mice with genetic deficiency or pharmacological blockade of P2X7R. Because abnormal dendritic branching is a hallmark of certain neurodevelopmental disorders, such as schizophrenia, a model of maternal immune activation (MIA)-induced schizophrenia, was used for further morphologic investigations. Subsequently, we studied MIA-induced behavioral deficits in young adult mice females and males. Genetic deficiency or pharmacological blockade of P2X7R led to branching deficits under physiological conditions. Moreover, pathologic activation of the receptor led to deficits in dendritic outgrowth on primary neurons from WT mice but not those from P2X7R KO mice exposed to MIA. Likewise, only MIA-exposed WT mice displayed schizophrenia-like behavioral and cognitive deficits. Therefore, we conclude that P2X7R has different roles in the development of hippocampal dendritic arborization under physiological and pathologic conditions.SIGNIFICANCE STATEMENT Our main finding is a novel role for P2X7R in neuronal branching in the early stages of development under physiological conditions. We show how a decrease in the expression of P2X7R during brain development causes the receptor to play pathologic roles in adulthood. Moreover, we studied a neurodevelopmental model of schizophrenia and found that, at higher ATP concentrations, endogenous activation of P2X7R is necessary and sufficient for the development of positive and cognitive symptoms.

Maternal Immune Activation Induced by Prenatal Lipopolysaccharide Exposure Leads to Long-Lasting Autistic-like Social, Cognitive and Immune Alterations in Male Wistar Rats

Several studies have supported the association between maternal immune activation (MIA) caused by exposure to pathogens or inflammation during critical periods of gestation and an increased susceptibility to the development of various psychiatric and neurological disorders, including autism and other neurodevelopmental disorders (NDDs), in the offspring. In the present work, we aimed to provide extensive characterization of the short- and long-term consequences of MIA in the offspring, both at the behavioral and immunological level. To this end, we exposed Wistar rat dams to Lipopolysaccharide and tested the infant, adolescent and adult offspring across several behavioral domains relevant to human psychopathological traits. Furthermore, we also measured plasmatic inflammatory markers both at adolescence and adulthood. Our results support the hypothesis of a deleterious impact of MIA on the neurobehavioral development of the offspring: we found deficits in the communicative, social and cognitive domains, together with stereotypic-like behaviors and an altered inflammatory profile at the systemic level. Although the precise mechanisms underlying the role of neuroinflammatory states in neurodevelopment need to be clarified, this study contributes to a better understanding of the impact of MIA on the risk of developing behavioral deficits and psychiatric illness in the offspring.

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.

Intrauterine Inflammation Leads to Select Sex- and Age-Specific Behavior and Molecular Differences in Mice

Sex-specific differences in behavior have been observed in anxiety and learning in children exposed to prenatal inflammation; however, whether these behaviors manifest differently by age is unknown. This study assesses possible behavioral changes due to in utero inflammation as a function of age in neonatal, juvenile, and adult animals and presents potential molecular targets for observed differences. CD-1 timed pregnant dams were injected in utero with lipopolysaccharide (LPS, 50 μg/animal) or saline at embryonic day 15. No differences in stress responses were measured by neonatal ultrasonic vocalizations between LPS- and saline-exposed groups of either sex. By contrast, prenatal inflammation caused a male-specific increase in anxiety in mature but not juvenile animals. Juvenile LPS-exposed females had decreased movement in open field testing that was not present in adult animals. We additionally observed improved memory retrieval after in utero LPS in the juvenile animals of both sexes, which in males may be related to a perseverative phenotype. However, there was an impairment of long-term memory in only adult LPS-exposed females. Finally, gene expression analyses revealed that LPS induced sex-specific changes in genes involved in hippocampal neurogenesis. In conclusion, intrauterine inflammation has age- and sex-specific effects on anxiety and learning that may correlate to sex-specific disruption of gene expression associated with neurogenesis in the hippocampus.

Dynamic changes in spatiotemporal transcriptome reveal maternal immune dysregulation of autism spectrum disorder

Maternal immune activation (MIA) during pregnancy is known to be an environmental risk factor for neurodevelopment and autism spectrum disorder (ASD). However, it is unclear at which fetal brain developmental windows and regions MIA induces ASD-related neurodevelopmental transcriptional abnormalities. The non-chasm differentially expressed genes (DEGs) involved in MIA inducing ASD during fetal brain developmental windows were identified by performing the differential expression analysis and comparing the common DEGs among MIA at four different gestational development windows, ASD with multiple brain regions from human patients and mouse models, and human and mouse embryonic brain developmental trajectory. The gene set and functional enrichment analyses were performing to identify MIA dysregulated ASD-related the fetal neurodevelopmental windows and brain regions and function annotations. Additionally, the networks were constructed using Cytoscape for visualization. MIA at E12.5 and E14.5 increased the risk of distinct brain regions for ASD. MIA-driven transcriptional alterations of non-chasm DEGs, during the coincidence brain developmental windows between human and mice, involving ASD-relevant synaptic components, as well as immune- and metabolism-related functions and pathways. Furthermore, a great number of non-chasm brain development-, immune-, and metabolism-related DEGs were overlapped in at least two existing ASD-associated databases, suggesting that the others could be considered as the candidate targets to construct the model mice for explaining the pathological changes of ASD when environmental factors (MIA) and gene mutation effects co-occur. Overall, our search supported that transcriptome-based MIA dysregulated the brain development-, immune-, and metabolism-related non-chasm DEGs at specific embryonic brain developmental window and region, leading to abnormal embryonic neurodevelopment, to induce the increasing risk of ASD.

A Possible Causal Involvement of Neuroinflammatory, Purinergic P2X7 Receptors in Psychiatric Disorders

P2X7 receptors (Rs) are prominent members of the P2XR family, which after binding ATP, open non-selective cationic channels, thereby allowing the transmembrane passage of Na+, Ca²⁺, and K+. Long-lasting and repetitive stimulation of the receptor by its agonist leads to the formation of large membrane pores permeable for organic cations of up to 900 Da molecular size. These pores are believed to play a role in apoptosis and inflammation. P2X7Rs are located primarily at peripheral macrophages and microglial cells, the resident macrophages of the CNS. The coactivation of toll-like receptors 4 (TLR4) by lipopolysaccharide, a constituent of the cell membrane of gram-negative bacteria, and the P2X7R by ATP leads to the generation and release of the proinflammatory cytokines interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α. Together with the microglial release of chemokines, reactive oxygen and nitrogen species, proteases, and excitotoxic glutamate, these cytokines result in neurodegeneration. P2X7Rs were found not only to amplify various neurodegenerative illnesses, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis, but also to participate in a range of psychiatric diseases, such as major depression, bipolar disorder, schizophrenia, and autism spectrum disorder. Based on the prevention/reversal of neuroinflammation, pharmacological antagonists of P2X7Rs and their genetic deletion in animal experiments counteract these deleterious psychiatric conditions. Hence, brain penetrant P2X7R antagonists are potential therapeutics for psychiatric diseases, although the available evidence still needs to be extended and validated by further clinical data.

Maternal pregnancy-related infections and autism spectrum disorder-the genetic perspective

Autism spectrum disorder (ASD) refers to a group of neurodevelopmental disorders which include deficits in behavior, social interaction and communication. ASD has a complex genetic architecture, and it is also influenced by certain environmental exposures. Both types of predisposing factors may be related to immunological mechanisms, involving, for example, immune system genes and infections. Past studies have shown an association between infections occurring during the pregnancy in the mother and increased risk of ASD in the child, an observation which has received recent support from experimental animal studies of ASD-like behavior. The aim of this study was to study the genetic contribution to this effect. We employed genetic correlation analyses across potential ASD subtypes stratified on the basis of maternal pregnancy-related infections within the iPSYCH ASD case-cohort sample, as well as a case-case GWAS. We validated the trends of the genetic correlation analyses observed in our sample using GWAS summary statistics from the PGC ASD study (excluding iPSYCH). The genetic correlation between ASD with a history of maternal pregnancy-related infections and ASD without a history of maternal infections in iPSYCH was rg = 0.3811. We obtained a similar estimate between the former and the PGC ASD phenotype (rg = 0.3997). Both estimates are lower compared to the genetic correlation between ASD without a history of maternal infections and the PGC ASD phenotype (rg = 0.6735), and between ASD with a history of maternal infections occurring only more than 2 months following childbirth and the PGC ASD phenotype (rg = 0.6293). Additionally, we observed genetic variance between the two main ASD phenotypes using summary statistics from the case-case GWAS in iPSYCH (h2cc = 0.1059), indicating genome-wide differences between the phenotypes. Our results suggest potentially different etiologies of ASD based on a history of maternal pregnancy-related infections, which may, in part, be genetic. This highlights the relevance of maternal pregnancy-related infections to genetic studies of ASD and provides new insights into the molecular underpinnings of ASD.

Interleukin 15 modulates the effects of poly I:C maternal immune activation on offspring behaviour

Maternal infections during pregnancy are linked with an increased risk for disorders like Autism Spectrum Disorder and schizophrenia in the offspring. Although precise mechanisms are still unclear, clinical and preclinical evidence suggest a strong role for maternal immune activation (MIA) in the neurodevelopmental disruptions caused by maternal infection. Previously, studies using the Polyinosinic:Polycytidylic (Poly I:C) MIA preclinical model showed that cytokines like Interleukin 6 (Il6) are important mediators of MIA's effects. In this study, we hypothesized that Il15 may similarly act as a mediator of Poly I:C MIA, given its role in the antiviral immune response. To test this hypothesis, we induced Poly I:C MIA at gestational day 9.5 in wildtype (WT) and Il15^−/− rat dams and tested their offspring in adolescence and adulthood. Poly I:C MIA and Il15 knockout produced both independent and synergistic effects on offspring behaviour. Poly I:C MIA decreased startle reactivity in adult WT offspring but resulted in increased adolescent anxiety and decreased adult locomotor activity in Il15^−/− offspring. In addition, Poly I:C MIA led to genotype-independent effects on locomotor activity and prepulse inhibition. Finally, we showed that Il15^−/− offspring exhibit distinct phenotypes that were unrelated to Poly I:C MIA including altered startle reactivity, locomotion and signal transduction in the auditory brainstem. Overall, our findings indicate that the lack of Il15 can leave offspring either more or less susceptible to Poly I:C MIA, depending on the phenotype in question. Future studies should examine the contribution of fetal versus maternal Il15 in MIA to determine the precise developmental mechanisms underlying these changes.

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Poly I:C MIA decreases startle reactivity in adult WT but not Il15^−/− offspring.

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Il15^−/− offspring exposed to Poly I:C MIA show altered PPI and open field exploration.

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Il15^−/− rats exhibit distinct behavioural phenotypes independent from MIA.

Association of Birth During the COVID-19 Pandemic With Neurodevelopmental Status at 6 Months in Infants With and Without In Utero Exposure to Maternal SARS-CoV-2 Infection

Importance

Associations between in utero exposure to maternal SARS-CoV-2 infection and neurodevelopment are speculated, but currently unknown.

Objective

To examine the associations between maternal SARS-CoV-2 infection during pregnancy, being born during the COVID-19 pandemic regardless of maternal SARS-CoV-2 status, and neurodevelopment at age 6 months.

Design, Setting, and Participants

A cohort of infants exposed to maternal SARS-CoV-2 infection during pregnancy and unexposed controls was enrolled in the COVID-19 Mother Baby Outcomes Initiative at Columbia University Irving Medical Center in New York City. All women who delivered at Columbia University Irving Medical Center with a SARS-CoV-2 infection during pregnancy were approached. Women with unexposed infants were approached based on similar gestational age at birth, date of birth, sex, and mode of delivery. Neurodevelopment was assessed using the Ages & Stages Questionnaire, 3rd Edition (ASQ-3) at age 6 months. A historical cohort of infants born before the pandemic who had completed the 6-month ASQ-3 were included in secondary analyses.

Exposures

Maternal SARS-CoV-2 infection during pregnancy and birth during the COVID-19 pandemic.

Main Outcomes and Measures

Outcomes were scores on the 5 ASQ-3 subdomains, with the hypothesis that maternal SARS-CoV-2 infection during pregnancy would be associated with decrements in social and motor development at age 6 months.

Results

Of 1706 women approached, 596 enrolled; 385 women were invited to a 6-month assessment, of whom 272 (70.6%) completed the ASQ-3. Data were available for 255 infants enrolled in the COVID-19 Mother Baby Outcomes Initiative (114 in utero exposed, 141 unexposed to SARS-CoV-2; median maternal age at delivery, 32.0 [IQR, 19.0-45.0] years). Data were also available from a historical cohort of 62 infants born before the pandemic. In utero exposure to maternal SARS-CoV-2 infection was not associated with significant differences on any ASQ-3 subdomain, regardless of infection timing or severity. However, compared with the historical cohort, infants born during the pandemic had significantly lower scores on gross motor (mean difference, -5.63; 95% CI, -8.75 to -2.51; F1,267 = 12.63; P<.005), fine motor (mean difference, -6.61; 95% CI, -10.00 to -3.21; F1,267 = 14.71; P < .005), and personal-social (mean difference, -3.71; 95% CI, -6.61 to -0.82; F1,267 = 6.37; P<.05) subdomains in fully adjusted models.

Conclusions and Relevance

In this study, birth during the pandemic, but not in utero exposure to maternal SARS-CoV-2 infection, was associated with differences in neurodevelopment at age 6 months. These early findings support the need for long-term monitoring of children born during the COVID-19 pandemic.

Sex Differences in Autism Spectrum Disorder: Diagnostic, Neurobiological, and Behavioral Features

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental disorder with a worldwide prevalence of about 1%, characterized by impairments in social interaction, communication, repetitive patterns of behaviors, and can be associated with hyper- or hypo-reactivity of sensory stimulation and cognitive disability. ASD comorbid features include internalizing and externalizing symptoms such as anxiety, depression, hyperactivity, and attention problems. The precise etiology of ASD is still unknown and it is undoubted that the disorder is linked to some extent to both genetic and environmental factors. It is also well-documented and known that one of the most striking and consistent finding in ASD is the higher prevalence in males compared to females, with around 70% of ASD cases described being males. The present review looked into the most significant studies that attempted to investigate differences in ASD males and females thus trying to shade some light on the peculiar characteristics of this prevalence in terms of diagnosis, imaging, major autistic-like behavior and sex-dependent uniqueness. The study also discussed sex differences found in animal models of ASD, to provide a possible explanation of the neurological mechanisms underpinning the different presentation of autistic symptoms in males and females.

Neurodevelopmental disorders, immunity, and cancer are connected

Immunity could be viewed as the common factor in neurodevelopmental disorders and cancer. The immune and nervous systems coevolve as the embryo develops. Immunity can release cytokines that activate MAPK signaling in neural cells. In specific embryonic brain cell types, dysregulated signaling that results from germline or embryonic mutations can promote changes in chromatin organization and gene accessibility, and thus expression levels of essential genes in neurodevelopment. In cancer, dysregulated signaling can emerge from sporadic somatic mutations during human life. Neurodevelopmental disorders and cancer share similarities. In neurodevelopmental disorders, immunity, and cancer, there appears an almost invariable involvement of small GTPases (e.g., Ras, RhoA, and Rac) and their pathways. TLRs, IL-1, GIT1, and FGFR signaling pathways, all can be dysregulated in neurodevelopmental disorders and cancer. Although there are signaling similarities, decisive differentiating factors are timing windows, and cell type specific perturbation levels, pointing to chromatin reorganization. Finally, we discuss drug discovery.

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.

Maternal inflammation and its ramifications on fetal neurodevelopment

Exposure to heightened inflammation in pregnancy caused by infections or other inflammatory insults has been associated with the onset of neurodevelopmental and psychiatric disorders in children. Rodent models have provided unique insights into how this maternal immune activation (MIA) disrupts brain development. Here, we discuss the key immune factors involved, highlight recent advances in determining the molecular and cellular pathways of MIA, and review how the maternal immune system affects fetal development. We also examine the roles of microbiomes in shaping maternal immune function and the development of autism-like phenotypes. A comprehensive understanding of the gut bacteria-immune-neuro interaction in MIA is essential for developing diagnostic and therapeutic measures for high-risk pregnant women and identifying targets for treating inflammation-induced neurodevelopmental disorders.

Timing of maternal immune activation and sex influence schizophrenia-relevant cognitive constructs and neuregulin and GABAergic pathways

Maternal immune activation (MIA) during pregnancy is an established environmental risk factor for schizophrenia. Timing of immune activation exposure as well as sex of the exposed offspring are critical factors in defining the effects of MIA. However, the specificity of MIA on the component structure of schizophrenia, especially cognition, has been difficult to assess due to a lack of translational validity of maze-like testing paradigms. We aimed to assess cognitive domains relevant to schizophrenia using highly translational touchscreen-based tasks in male and female mice exposed to the viral mimetic, poly(I:C) (5 mg/k, i.p.), during early (gestational day (GD) 9-11) and late (GD13-15) gestational time points. Gene expression of schizophrenia candidate pathways were assessed in fetal brain immediately following poly(I:C) exposure and in adulthood to identify its influence on neurodevelopmental processes. Sex and window specific alterations in cognitive performance were found with the early window of MIA exposure causing female-specific disruptions to working memory and reduced perseverative behaviour, while late MIA exposure caused male-specific changes to working memory and deficits in reversal learning. GABAergic specification marker, Nkx2.1 gene expression was reduced in fetal brains and reelin expression was reduced in adult hippocampus of both early and late poly(I:C) exposed mice. Neuregulin and EGF signalling were initially upregulated in the fetal brain, but were reduced in the adult hippocampus, with male mice exposed in the late window showing reduced Nrg3 expression. Serine racemase was reduced in both fetal and adult brain, but again, adult reductions were specific to male mice exposed at the late time point. Overall, we show that cognitive constructs relevant to schizophrenia are altered by in utero exposure to maternal immune activation, but are highly dependent on the timing of infection and the sex of the offspring. Glutamatergic and epidermal growth factor pathways were similarly altered by MIA in a timing and sex dependent manner, while MIA-induced GABAergic deficits were independent of timing or sex.

Emerging evidence of Toll-like receptors as a putative pathway linking maternal inflammation and neurodevelopmental disorders in human offspring: A systematic review

Inflammation is increasingly recognised to play a major role in gene-environment interactions in neurodevelopmental disorders (NDDs). The effects of aberrant immune responses to environmental stimuli in the mother and in the child can affect neuroimmune signalling that is central to brain development. Toll-like receptors (TLR) are the best known innate immune pattern and danger recognition sensors to various environmental threats. In animal models, maternal immune activation (MIA), secondary to inflammatory factors including maternal gestational infection, obesity, diabetes, and stress activate the TLR pathway in maternal blood, placenta, and fetal brain, which correlate with offspring neurobehavioral abnormalities. Given the central role of TLR activation in animal MIA models, we systematically reviewed the human evidence for TLR activation and response to stimulation across the maternal-fetal interface. Firstly, we included 59 TLR studies performed in peripheral blood of adults in general population (outside of pregnancy) with six chronic inflammatory factors which have epidemiological evidence for increased risk of offspring NDDs, namely, obesity, diabetes mellitus, depression, low socio-economic status, autoimmune diseases, and asthma. Secondly, eight TLR studies done in human pregnancies with chronic inflammatory factors, involving maternal blood, placenta, and cord blood, were reviewed. Lastly, ten TLR studies performed in peripheral blood of individuals with NDDs were included. Despite these studies, there were no studies which examined TLR function in both the pregnant mother and their offspring. Increased TLR2 and TLR4 mRNA and/or protein levels in peripheral blood were common in obesity, diabetes mellitus, depression, autoimmune thyroid disease, and rheumatoid arthritis. To a lesser degree, TLR 3, 7, 8, and 9 activation were found in peripheral blood of humans with autoimmune diseases and depression. In pregnancy, increased TLR4 mRNA levels were found in the peripheral blood of women with diabetes mellitus and systemic lupus erythematosus. Placental TLR activation was found in mothers with obesity or diabetes. Postnatally, dysregulated TLR response to stimulation was found in peripheral blood of individuals with NDDs. This systematic review found emerging evidence that TLR activation may represent a mechanistic link between maternal inflammation and offspring NDD, however the literature is incomplete and longitudinal outcome studies are lacking. Identification of pathogenic mechanisms in MIA could create preventive and therapeutic opportunities to mitigate NDD prevalence and severity.

Double trouble: Prenatal immune activation in stress sensitive offspring

Viral infections during pregnancy are associated with increased incidence of psychiatric disorders in offspring. The pathological outcomes of viral infection appear to be caused by the deleterious effects of innate immune response-associated factors on development of the fetus, which predispose the offspring to pathological conditions in adulthood. The negative impact of viral infections varies substantially between pregnancies. Here, we explored whether differential stress sensitivity underlies the high heterogeneity of immune reactivity and whether this may influence the pathological consequences of maternal immune activation. Using mouse models of social dominance (Dom) and submissiveness (Sub), which possess innate features of stress resilience and vulnerability, respectively, we identified differential immune reactivity to the synthetic analogue of viral double-stranded RNA, Poly(I:C), in Sub and Dom nulliparous and pregnant females. More specifically, we found that Sub females showed an exacerbated pro- and anti-inflammatory cytokine response to Poly(I:C) as compared with Dom females. Sub offspring born to Sub mothers (stress sensitive offspring) showed enhanced locomotory response to the non-competitive NMDA antagonist, MK-801, which was potentiated by prenatal Poly(I:C) exposure. Our findings suggest that inherited stress sensitivity may lead to functional changes in glutamatergic signaling, which in turn is further exacerbated by prenatal exposure to viral-like infection. The maternal immunome seems to play a crucial role in these observed phenomena.