Effects of early or late prenatal immune activation in mice on behavioral and neuroanatomical abnormalities relevant to schizophrenia in the adulthood

[Research progress on the mechanism of the impact of maternal childhood trauma on intergenerational transmission]

Childhood trauma refers to trauma experiences encountered during childhood and adolescence. Maternal childhood trauma experiences have a lasting impact on the next generation, affecting their physical and mental well-being. The mechanisms involved include the hypothalamic-pituitary-adrenal axis, inflammatory factors, brain structure and function, gene interactions, and parenting styles. This paper systematically reviews the mechanisms of the impact of maternal childhood trauma on intergenerational transmission, providing insights for the prevention of intergenerational transmission of childhood trauma.

Investigating behavioral phenotypes related to autism spectrum disorder in a gene-environment interaction model of Cntnap2 deficiency and Poly I:C maternal immune activation

Introduction

Autism Spectrum Disorder (ASD) has been associated with a wide variety of genetic and environmental risk factors in both human and preclinical studies. Together, findings support a gene-environment interaction hypothesis whereby different risk factors independently and synergistically impair neurodevelopment and lead to the core symptoms of ASD. To date, this hypothesis has not been commonly investigated in preclinical ASD models. Mutations in the Contactin-associated protein-like 2 (Cntnap2) gene and exposure to maternal immune activation (MIA) during pregnancy have both been linked to ASD in humans, and preclinical rodent models have shown that both MIA and Cntnap2 deficiency lead to similar behavioral deficits.

Methods

In this study, we tested the interaction between these two risk factors by exposing Wildtype, Cntnap2+/–, and Cntnap2–/– rats to Polyinosinic: Polycytidylic acid (Poly I:C) MIA at gestation day 9.5.

Results

Our findings showed that Cntnap2 deficiency and Poly I:C MIA independently and synergistically altered ASD-related behaviors like open field exploration, social behavior, and sensory processing as measured through reactivity, sensitization, and pre-pulse inhibition (PPI) of the acoustic startle response. In support of the double-hit hypothesis, Poly I:C MIA acted synergistically with the Cntnap2–/– genotype to decrease PPI in adolescent offspring. In addition, Poly I:C MIA also interacted with the Cntnap2+/– genotype to produce subtle changes in locomotor hyperactivity and social behavior. On the other hand, Cntnap2 knockout and Poly I:C MIA showed independent effects on acoustic startle reactivity and sensitization.

Discussion

Together, our findings support the gene-environment interaction hypothesis of ASD by showing that different genetic and environmental risk factors could act synergistically to exacerbate behavioral changes. In addition, by showing the independent effects of each risk factor, our findings suggest that ASD phenotypes could be caused by different underlying mechanisms.

Adolescent raloxifene treatment in females prevents cognitive deficits in a neurodevelopmental rodent model of schizophrenia

The existence of sex differences in schizophrenia is a well documented phenomenon which led to the hypothesis that female sex hormones are neuroprotective and hence responsible for the more favorable disease characteristics seen in women. The current study sought to investigate the effects of estrogen-like agents administered during early adolescence on behavioral outcomes in adulthood using the neurodevelopmental maternal immune activation (MIA) rodent model of schizophrenia. Female MIA offspring were administered during the asymptomatic period of adolescence with either 17β-estradiol, raloxifene or saline and were tested in late adolescence and adulthood for schizophrenia-related behavioral performance. We report here that whereas adult female MIA offspring exhibited cognitive deficits in the form of retarded spatial learning, the administration of raloxifene during adolescence was sufficient in preventing these deficits and resulted in intact performance in the MIA group.

The Poly I:C maternal immune stimulation model shows unique patterns of brain metabolism, morphometry, and plasticity in female rats

Introduction: Prenatal infections are associated with an increased risk of the onset of schizophrenia. Rodent models of maternal immune stimulation (MIS) have been extensively used in preclinical studies. However, many of these studies only include males, omitting pathophysiological features unique to females. The aim of this study is to characterize the MIS model in female rats using positron emission tomography (PET), structural magnetic resonance imaging (MR), and neuroplasticiy studies. Methods: In gestational day 15, Poly I:C (or Saline) was injected into pregnant Wistar rats to induce the MIS model. Imaging studies: [¹⁸F]-fluoro-2-deoxy-D-glucose-PET scans of female-offspring were acquired at post-natal day (PND) 35 and PND100. Furthermore, T2-MR brain images were acquired in adulthood. Differences in FDG uptake and morphometry between groups were assessed with SPM12 and Regions of Interest (ROI) analyses. Ex vivo study: The density of parvalbumin expressing interneurons (PV), perineuronal nets (PNN), and parvalbumin expressing interneurons surrounded by perineuronal nets (PV-PNN) were evaluated in the prelimbic cortex and basolateral amygdala using confocal microscopy. ROIs and neuroplasticity data were analyzed by 2-sample T-test and 2-way-ANOVA analyses, respectively. Results: A significant increase in brain metabolism was found in all animals at adulthood compared to adolescence. MIS hardly modified brain glucose metabolism in females, highlighting a significant hypometabolism in the thalamus at adulthood. In addition, MIS induced gray matter (GM) enlargements in the pituitary, hippocampus, substantia nigra, and cingulate cortex, and GM shrinkages in some thalamic nuclei, cerebelar areas, and brainstem. Moreover, MIS induced white matter shrinkages in the cerebellum, brainstem and corpus callosum, along with cerebrospinal fluid enlargements in the lateral and 4th ventricles. Finally, MIS reduced the density of PV, PNN, and PV-PNN in the basolateral amygdala. Conclusion: Our work showed in vivo the differential pattern of functional and morphometric affectation in the MIS model in females, as well as the deficits caused at the synaptic level according to sex. The differences obtained highlight the relevance of including both sexes in psychiatric research in order to consider their pathophysiological particularities and successfully extend the benefits obtained to the entire patient population.

Systemic Inflammation Causes Microglial Dysfunction With a Vascular AD phenotype

Background

Studies in rodents and humans have indicated that inflammation outside CNS (systemic inflammation) affects brain homeostasis contributing to neurodevelopmental disorders. Itis becoming increasingly evident that such early insults may also belinked to neurodegenerative diseases like late-onset Alzheimer's disease (AD). Importantly, lifestyle and stress, such as viral or bacterial infection causing chronic inflammation, may contribute to neurodegenerative dementia. Systemic inflammatory response triggers a cascade of neuroinflammatory responses, altering brain transcriptome, cell death characteristic of AD, and vascular dementia. Our study aimed to assess the temporal evolution of the pathological impact of systemic inflammation evoked by prenatal and early postnatal peripheral exposure of viral mimetic Polyinosinic:polycytidylic acid (PolyI:C) and compare the hippocampal transcriptomic changes with the profiles of human post-mortem AD and vascular dementia brain specimens.

Methods

We have engineered the PolyI:C sterile infection model in wildtype C57BL6 mice to achieve chronic low-grade systemic inflammation. We have conducted a cross-sectional analysis of aging PolyI:C and Saline control mice (3 months, 6 months, 9 months, and 16 months), taking the hippocampus as a reference brain region, and compared the brain aging phenotype to AD progression in humans with mild AD, severe AD, and Controls (CTL), in parallel to Vascular dementia (VaD) patients' specimens.

Results

We found that PolyI:C mice display both peripheral and central inflammation with a peak at 6 months, associated with memory deficits. The hippocampus is characterized by a pronounced and progressive tauopathy. In PolyI:C brains, microglia undergo aging-dependent morphological shifts progressively adopting a phagocytic phenotype. Transcriptomic analysis reveals a profound change in gene expression throughout aging, with a peak in differential expression at 9 months. We show that the proinflammatory marker Lcn2 is one of the genes with the strongest upregulation in PolyI:C mice upon aging. Validation in brains from patients with increasing severity of AD and VaD shows the reproducibility of some gene targets in vascular dementia specimens as compared to AD ones.

Conclusions

The PolyI:C model of sterile infection demonstrates that peripheral chronic inflammation causes progressive tau hyperphosphorylation, changes in microglia morphology, astrogliosis and gene reprogramming reflecting increased neuroinflammation, vascular remodeling, and the loss of neuronal functionality seen to some extent in human AD and Vascular dementia suggesting early immune insults could be crucial in neurodegenerative diseases.

The instrumental role of operant paradigms in translational psychiatric research: Insights from a maternal immune activation model of schizophrenia risk

Rigorous behavioral analysis is essential to the translation of research conducted using animal models of neuropsychiatric disease. Here we discuss the use of operant paradigms within our lab as a powerful approach for exploring the biobehavioral bases of disease in the maternal immune activation rat model of schizophrenia. We have investigated a range of disease features in schizophrenia including abnormal perception of time, cognition, learning, motivation, and internal state (psychosis), providing complex insights into brain and behavior. Beyond simple phenotyping, implementing sophisticated operant procedures has been effective in delineating aspects of pathological behavior, identifying interacting pathologies, and isolating contributing mechanisms of disease. We provide comment on the strengths of operant techniques to support high-quality behavioral investigations in fundamental neuropsychiatric research.

LPS vs. Poly I:C Model: Comparison of Long-Term Effects of Bacterial and Viral Maternal Immune Activation (MIA) on the Offspring

A prominent health issue nowadays is the COVID-19 pandemic, which poses acute risks to human health. However, the long-term health consequences are largely unknown and cannot be neglected. An especially vulnerable period for infection is pregnancy, when infections could have long-term health effect on the child. Evidence suggests that maternal immune activation (MIA) induced by either bacteria or viruses presents various effects on the offspring, leading to adverse phenotypes in many organ systems. This review compares the mechanisms of bacterial and viral MIA and the possible long-term outcomes for the offspring by summarizing the outcome in animal LPS and Poly I:C models. Both models are activated immune responses mediated by Toll-like receptors. The outcomes for MIA offspring include neurodevelopment, immune response, circulation, metabolism, and reproduction. Some of these changes continue to exist until later life. Besides different doses and batches of LPS and Poly I:C, the injection day, administration route, and also different animal species influence the outcomes. Here, we specifically aim to support colleagues when choosing their animal models for future studies.

Effects of maternal psychological stress during pregnancy on offspring brain development: Considering the role of inflammation and potential for preventive intervention

Heightened psychological stress during pregnancy has repeatedly been associated with increased risk for offspring development of behavior problems and psychiatric disorders. This review covers a rapidly growing body of research with the potential to advance a mechanistic understanding of these associations grounded in knowledge about maternal-placental-fetal stress biology and fetal brain development. Specifically, we highlight research employing magnetic resonance imaging to examine the infant brain soon after birth in relation to maternal psychological stress during pregnancy to increase capacity to identify specific alterations in brain structure and function and to differentiate between effects of pre- versus postnatal exposures. We then focus on heightened maternal inflammation during pregnancy as a mechanism through which maternal stress influences the developing fetal brain based on extensive preclinical literature and emerging research in humans. We place these findings in the context of recent work identifying psychotherapeutic interventions found to be effective for reducing psychological stress among pregnant individuals, which also show promise for reducing inflammation. We argue that a focus on inflammation, among other mechanistic pathways, has the potential to lead to a productive and necessary integration of research focused on the effects of maternal psychological stress on offspring brain development and prevention and intervention studies aimed at reducing maternal psychological stress during pregnancy. In addition to increasing capacity for common measurements and understanding potential mechanisms of action relevant to maternal mental health and fetal neurodevelopment, this focus can inform and broaden thinking about prevention and intervention strategies.

An Examination of the Long-Term Neurodevelopmental Impact of Prenatal Zika Virus Infection in a Rat Model Using a High Resolution, Longitudinal MRI Approach

Since Zika virus (ZIKV) first emerged as a public health concern in 2015, our ability to identify and track the long-term neurological sequelae of prenatal Zika virus (ZIKV) infection in humans has been limited. Our lab has developed a rat model of maternal ZIKV infection with associated vertical transmission to the fetus that results in significant brain malformations in the neonatal offspring. Here, we use this model in conjunction with longitudinal magnetic resonance imaging (MRI) to expand our understanding of the long-term neurological consequences of prenatal ZIKV infection in order to identify characteristic neurodevelopmental changes and track them across time. We exploited both manual and automated atlas-based segmentation of MR images in order to identify long-term structural changes within the developing rat brain following inoculation. The paradigm involved scanning three cohorts of male and female rats that were prenatally inoculated with 10⁷ PFU ZIKV, 10⁷ UV-inactivated ZIKV (iZIKV), or diluent medium (mock), at 4 different postnatal day (P) age points: P2, P16, P24, and P60. Analysis of tracked brain structures revealed significantly altered development in both the ZIKV and iZIKV rats. Moreover, we demonstrate that prenatal ZIKV infection alters the growth of brain regions throughout the neonatal and juvenile ages. Our findings also suggest that maternal immune activation caused by inactive viral proteins may play a role in altered brain growth throughout development. For the very first time, we introduce manual and automated atlas-based segmentation of neonatal and juvenile rat brains longitudinally. Experimental results demonstrate the effectiveness of our novel approach for detecting significant changes in neurodevelopment in models of early-life infections.

Behavioral Tasks Evaluating Schizophrenia-like Symptoms in Animal Models: A Recent Update

BACKGROUND

Schizophrenia is a serious mental illness that affects more than 21 million people worldwide. Both genetics and the environment play a role in its etiology and pathogenesis. Symptoms of schizophrenia are mainly categorized into positive, negative, and cognitive. One major approach to identify and understand these diverse symptoms in humans has been to study behavioral phenotypes in a range of animal models of schizophrenia.

OBJECTIVE

We aimed to provide a comprehensive review of the behavioral tasks commonly used for measuring schizophrenia-like behaviors in rodents together with an update of the recent study findings.

METHODS

Articles describing phenotypes of schizophrenia-like behaviors in various animal models were collected through a literature search in Google Scholar, PubMed, Web of Science, and Scopus, with a focus on advances over the last 10 years.

RESULTS

Numerous studies have used a range of animal models and behavioral paradigms of schizophrenia to develop antipsychotic drugs for improved therapeutics. In establishing animal models of schizophrenia, the candidate models were evaluated for schizophrenia-like behaviors using several behavioral tasks for positive, negative, and cognitive symptoms designed to verify human symptoms of schizophrenia. Such validated animal models were provided as rapid preclinical avenues for drug testing and mechanistic studies.

CONCLUSION

Based on the most recent advances in the field, it is apparent that a myriad of behavior tests are needed to confirm and evaluate the congruency of animal models with the numerous behaviors and clinical signs exhibited by patients with schizophrenia.

What Does Immunology Have to Do With Normal Brain Development and the Pathophysiology Underlying Tourette Syndrome and Related Neuropsychiatric Disorders?

Objective: The goal of this article is to review the past decade's literature and provide a critical commentary on the involvement of immunological mechanisms in normal brain development, as well as its role in the pathophysiology of Tourette syndrome, other Chronic tic disorders (CTD), and related neuropsychiatric disorders including Obsessive-compulsive disorder (OCD) and Attention deficit hyperactivity disorder (ADHD). Methods: We conducted a literature search using the Medline/PubMed and EMBASE electronic databases to locate relevant articles and abstracts published between 2009 and 2020, using a comprehensive list of search terms related to immune mechanisms and the diseases of interest, including both clinical and animal model studies. Results: The cellular and molecular processes that constitute our "immune system" are crucial to normal brain development and the formation and maintenance of neural circuits. It is also increasingly evident that innate and adaptive systemic immune pathways, as well as neuroinflammatory mechanisms, play an important role in the pathobiology of at least a subset of individuals with Tourette syndrome and related neuropsychiatric disorders In the conceptual framework of the holobiont theory, emerging evidence points also to the importance of the "microbiota-gut-brain axis" in the pathobiology of these neurodevelopmental disorders. Conclusions: Neural development is an enormously complex and dynamic process. Immunological pathways are implicated in several early neurodevelopmental processes including the formation and refinement of neural circuits. Hyper-reactivity of systemic immune pathways and neuroinflammation may contribute to the natural fluctuations of the core behavioral features of CTD, OCD, and ADHD. There is still limited knowledge of the efficacy of direct and indirect (i.e., through environmental modifications) immune-modulatory interventions in the treatment of these disorders. Future research also needs to focus on the key molecular pathways through which dysbiosis of different tissue microbiota influence neuroimmune interactions in these disorders, and how microbiota modification could modify their natural history. It is also possible that valid biomarkers will emerge that will guide a more personalized approach to the treatment of these disorders.

Brain Structural and Functional Alterations in Mice Prenatally Exposed to LPS Are Only Partially Rescued by Anti-Inflammatory Treatment

Aberrant immune activity during neurodevelopment could participate in the generation of neurological dysfunctions characteristic of several neurodevelopmental disorders (NDDs). Numerous epidemiological studies have shown a link between maternal infections and NDDs risk; animal models of maternal immune activation (MIA) have confirmed this association. Activation of maternal immune system during pregnancy induces behavioral and functional alterations in offspring but the biological mechanisms at the basis of these effects are still poorly understood. In this study, we investigated the effects of prenatal lipopolysaccharide (LPS) exposure in peripheral and central inflammation, cortical cytoarchitecture and behavior of offspring (LPS-mice). LPS-mice reported a significant increase in interleukin-1β (IL-1β) serum level, glial fibrillary acidic protein (GFAP)- and ionized calcium-binding adapter molecule 1 (Iba1)-positive cells in the cortex. Furthermore, cytoarchitecture analysis in specific brain areas, showed aberrant alterations in minicolumns’ organization in LPS-mice adult brain. In addition, we demonstrated that LPS-mice presented behavioral alterations throughout life. In order to better understand biological mechanisms whereby LPS induced these alterations, dams were treated with meloxicam. We demonstrated for the first time that exposure to LPS throughout pregnancy induces structural permanent alterations in offspring brain. LPS-mice also present severe behavioral impairments. Preventive treatment with meloxicam reduced inflammation in offspring but did not rescue them from structural and behavioral alterations.

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

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

Neuropsychiatric consequences of childhood group A streptococcal infection: A systematic review of preclinical models

In recent years, clinical studies have shown strong epidemiological evidence of an increased risk of developing neuropsychiatric disorders after childhood exposure to streptococcal infection, including the Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infection (PANDAS). New preclinical studies on group A streptococcus (GAS) exposure investigate how to disentangle the influences of immune activation to induce long-term neurobehavioral effects associated with neuropsychiatric disorders such as obsessive-compulsive disorder, schizophrenia or autism. The present systematic review collects neurobehavioral evidence regarding the use of GAS exposure in animal models to study the vulnerability to different neuropsychiatric disorders, improving our understanding of its possible causes and consequences, and compares its contribution with other preclinical models of immune activation in a variety of paradigms. Specifically, we reviewed the effects of postnatal GAS exposure, in comparison with post- and prenatal exposure to Lipopolysaccharide (LPS) and Polyinosinic:polycytidylic acid (Poly I:C), on the long-term effects concerning psychomotor, cognition and socioemotional outcomes in rodents. GAS exposure in animal models has revealed different behavioral alterations such as reduced locomotion and motor coordination, a deficit in sensorimotor gating, learning, working memory, altered social behavior, and increased anxiety and stereotyped behavior. Most of the results found are in accordance with other immune activation models -LPS and Poly I:C-, with some discrepancies. The systematic review of the literature supports the preclinical model of GAS exposure as a valid model for studying the neurobehavioral consequences of streptococcal infections. Future studies on streptococcal infection could contribute increasing our knowledge on preventive actions or treatments for neuropsychiatric disorders.

Maternal Immune Activation by Poly I:C as a preclinical Model for Neurodevelopmental Disorders: A focus on Autism and Schizophrenia

Maternal immune activation (MIA) in response to a viral infection during early and mid-gestation has been linked through various epidemiological studies to a higher risk for the child to develop autism or schizophrenia-related symptoms.. This has led to the establishment of the pathogen-free poly I:C-induced MIA animal model for neurodevelopmental disorders, which shows relatively high construct and face validity. Depending on the experimental variables, particularly the timing of poly I:C administration, different behavioural and molecular phenotypes have been described that relate to specific symptoms of neurodevelopmental disorders such as autism spectrum disorder and/or schizophrenia. We here review and summarize epidemiological evidence for the effects of maternal infection and immune activation, as well as major findings in different poly I:C MIA models with a focus on poly I:C exposure timing, behavioural and molecular changes in the offspring, and characteristics of the model that relate it to autism spectrum disorder and schizophrenia.

Maternal Immune Activation and the Development of Dopaminergic Neurotransmission of the Offspring: Relevance for Schizophrenia and Other Psychoses

Prenatal infections have been linked to the development of schizophrenia (SCZ) and other neurodevelopmental disorders in the offspring, and work in animal models indicates that this is to occur through the maternal inflammatory response triggered by infection. Several studies in animal models demonstrated that acute inflammatory episodes are sufficient to trigger brain alterations in the adult offspring, especially in the mesolimbic dopamine (DA) system, involved in the pathophysiology of SCZ and other disorders involving psychosis. In the current review, we synthesize the literature on the clinical studies implicating prenatal infectious events in the development of SCZ. Then, we summarize evidence from animal models of maternal immune activation (MIA) and the behavioral and molecular alterations relevant for the function of the DAergic system. Furthermore, we discuss the evidence supporting the involvement of maternal cytokines, such as interleukin 6 (IL-6) and leptin (a hormone with effects on inflammation) in mediating the effects of MIA on the fetal brain, leading to the long-lasting effects on the offspring. In particular, IL-6 has been involved in mediating the effects of MIA animal models in the offspring through actions on the placenta, induction of IL-17a, or triggering the decrease in non-heme iron (hypoferremia). Maternal infection is very likely interacting with additional genetic and environmental risk factors in the development of SCZ; systematically investigating how these interactions produce specific phenotypes is the next step in understanding the etiology of complex psychiatric disorders.

The Potential Role of Dysfunctions in Neuron-Microglia Communication in the Pathogenesis of Brain Disorders

The bidirectional communication between neurons and microglia is fundamental for the proper functioning of the central nervous system (CNS). Chemokines and clusters of differentiation (CD) along with their receptors represent ligand-receptor signalling that is uniquely important for neuron - microglia communication. Among these molecules, CX3CL1 (fractalkine) and CD200 (OX-2 membrane glycoprotein) come to the fore because of their cell-type-specific localization. They are principally expressed by neurons when their receptors, CX3CR1 and CD200R, respectively, are predominantly present on the microglia, resulting in the specific axis which maintains the CNS homeostasis. Disruptions to this balance are suggested as contributors or even the basis for many neurological diseases. In this review, we discuss the roles of CX3CL1, CD200 and their receptors in both physiological and pathological processes within the CNS. We want to underline the critical involvement of these molecules in controlling neuron - microglia communication, noting that dysfunctions in their interactions constitute a key factor in severe neurological diseases, such as schizophrenia, depression and neurodegeneration-based conditions.

Maternal immune activation during pregnancy impacts on brain structure and function in the adult offspring

Gestational infection constitutes a risk factor for the occurrence of psychiatric disorders in the offspring. Activation of the maternal immune system (MIA) with subsequent impact on the development of the fetal brain is considered to form the neurobiological basis for aberrant neural wiring and the psychiatric manifestations later in offspring life. The examination of validated animal models constitutes a premier resource for the investigation of the neural underpinnings. Here we used a mouse model of MIA based upon systemic treatment of pregnant mice with Poly(I:C) (polyriboinosinic-polyribocytidilic acid), for the unbiased and comprehensive analysis of the impact of MIA on adult offspring brain activity, morphometry, connectivity and function by a magnetic resonance imaging (MRI) approach. Overall lower neural activity, smaller brain regions and less effective fiber structure were observed for Poly(I:C) offspring compared to the control group. The corpus callosum was significantly smaller and presented with a disruption in myelin/ fiber structure in the MIA progeny. Subsequent resting-state functional MRI experiments demonstrated a paralleling dysfunctional interhemispheric connectivity. Additionally, while the overall flow of information was intact, cortico-limbic connectivity was hampered and limbic circuits revealed hyperconnectivity in Poly(I:C) offspring. Our study sheds new light on the impact of maternal infection during pregnancy on the offspring brain and identifies aberrant resting-state functional connectivity patterns as possible correlates of the behavioral phenotype with relevance for psychiatric disorders.

In-depth characterization of congenital Zika syndrome in immunocompetent mice: Antibody-dependent enhancement and an antiviral peptide therapy

BACKGROUND

Zika virus (ZIKV) infection during pregnancy may cause major congenital defects, including microcephaly, ocular, articular and muscle abnormalities, which are collectively defined as Congenital Zika Syndrome. Here, we performed an in-depth characterization of the effects of congenital ZIKV infection (CZI) in immunocompetent mice.

METHODS

Pregnant dams were inoculated with ZIKV on embryonic day 5.5 in the presence or absence of a sub-neutralizing dose of a pan-flavivirus monoclonal antibody (4G2) to evaluate the potential role of antibody-dependent enhancement phenomenon (ADE) during short and long outcomes of CZI.

FINDINGS

ZIKV infection induced maternal immune activation (MIA), which was associated with occurrence of foetal abnormalities and death. Therapeutic administration of AH-D antiviral peptide during the early stages of pregnancy prevented ZIKV replication and death of offspring. In the post-natal period, CZI was associated with a decrease in whole brain volume, ophthalmologic abnormalities, changes in testicular morphology, and disruption in bone microarchitecture. Some alterations were enhanced in the presence of 4G2 antibody.

INTERPRETATION

Our results reveal that early maternal ZIKV infection causes several birth defects in immunocompetent mice, which can be potentiated by ADE phenomenon and are associated with MIA. Additionally, antiviral treatment with AH-D peptide may be beneficial during early maternal ZIKV infection. FUND: This work was supported by the Brazilian National Science Council (CNPq, Brazil), Minas Gerais Foundation for Science (FAPEMIG), Funding Authority for Studies and Projects (FINEP), Coordination of Superior Level Staff Improvement (CAPES), National Research Foundation of Singapore and Centre for Precision Biology at Nanyang Technological University.

Neuroinflammation as a risk factor for attention deficit hyperactivity disorder

Attention Deficit Hyperactivity Disorder (ADHD) is a persistent, and impairing pediatric-onset neurodevelopmental condition. Its high prevalence, and recurrent controversy over its widespread identification and treatment, drive strong interest in its etiology and mechanisms. Emerging evidence for a role for neuroinflammation in ADHD pathophysiology is of great interest. This evidence includes 1) the above-chance comorbidity of ADHD with inflammatory and autoimmune disorders, 2) initial studies indicating an association with ADHD and increased serum cytokines, 3) preliminary evidence from genetic studies demonstrating associations between polymorphisms in genes associated with inflammatory pathways and ADHD, 4) emerging evidence that early life exposure to environmental factors may increase risk for ADHD via an inflammatory mechanism, and 5) mechanistic evidence from animal models of maternal immune activation documenting behavioral and neural outcomes consistent with ADHD. Prenatal exposure to inflammation is associated with changes in offspring brain development including reductions in cortical gray matter volume and the volume of certain cortical areas -parallel to observations associated with ADHD. Alterations in neurotransmitter systems, including the dopaminergic, serotonergic and glutamatergic systems, are observed in ADHD populations. Animal models provide strong evidence that development and function of these neurotransmitters systems are sensitive to exposure to in utero inflammation. In summary, accumulating evidence from human studies and animal models, while still incomplete, support a potential role for neuroinflammation in the pathophysiology of ADHD. Confirmation of this association and the underlying mechanisms have become valuable targets for research. If confirmed, such a picture may be important in opening new intervention routes.

The adaptive immune and stress responses of adult female CD1 mice following exposure to a viral mimetic

Exposure to a bacterial endotoxin during puberty induces long-term changes to reproductive and non-reproductive behaviours. While the underlying mechanisms remain unknown, we have recently shown that there are age and sex differences in acute immune and stress responses following immune challenge. Given that it is unclear whether viral infections result in similar age and sex differences, the objective of this study was to examine the acute immune and stress responses following exposure to polyinosinic:polycytidylic acid (poly(I:C)), a viral mimetic, in CD1 mice and to investigate the role of gonadal hormones in these responses. CD1 male and female mice underwent sham-surgery or gonadectomy at 5 or 9 weeks of age. Following one week of recovery, at 6 (pubertal group) or 10 (adult group) weeks of age, mice were treated with either saline or poly(I:C). Poly(I:C) treatment induced greater sickness behaviour in males compared to females and increased peripheral corticosterone in adult mice relative to their pubertal counterparts. Changes in body temperature and central c-Fos expression were more prominent in adult females. Gonadectomy worsened poly(I:C)-induced sickness behaviour and altered body temperature in both sexes. The results demonstrate that adult females display the most pronounced acute changes in body temperature, corticosterone release, and c-Fos expression but show the fastest recovery in sickness behavior, indicating that, compared to males, females display an adaptive physiological response following immune stress due to higher circulating estradiol and progesterone.

Hypersynchronicity in the default mode-like network in a neurodevelopmental animal model with relevance for schizophrenia

BACKGROUND

Immune activation during pregnancy is an important risk factor for schizophrenia. Brain dysconnectivity and NMDA receptor (NMDAR) hypofunction have been postulated to be central to schizophrenia pathophysiology. The aim of this study was to investigate resting-state functional connectivity (resting-state functional MRI-rsfMRI), microstructure (diffusion tension imaging-DTI) and response to NMDAR antagonist (pharmacological fMRI-phMRI) using multimodal MRI in offspring of pregnant dams exposed to immune challenge (maternal immune activation-MIA model), and determine whether these neuroimaging readouts correlate with schizophrenia-related behaviour.

METHODS

Pregnant rats were injected with Poly I:C or saline on gestational day 15. The maternal weight response was assessed. Since previous research has shown behavioural deficits can differ between MIA offspring dependent on the maternal response to immune stimulus, offspring were divided into three groups: controls (saline, n = 11), offspring of dams that gained weight (Poly I:C WG, n = 12) and offspring of dams that lost weight post-MIA (Poly I:C WL, n = 16). Male adult offspring were subjected to rsfMRI, DTI, phMRI with NMDAR antagonist, behavioural testing and histological assessment.

RESULTS

Poly I:C WL offspring exhibited increased functional connectivity in default mode-like network (DMN). Poly I:C WG offspring showed the most pronounced attenuation in NMDAR antagonist response versus controls. DTI revealed no differences in Poly I:C offspring versus controls. Poly I:C offspring exhibited anxiety.

CONCLUSIONS

MIA offspring displayed a differential pathophysiology depending on the maternal response to immune challenge. While Poly I:C WL offspring displayed hypersynchronicity in the DMN, altered NMDAR antagonist response was most pronounced in Poly I:C WG offspring.

Brain changes in a maternal immune activation model of neurodevelopmental brain disorders

The developing brain is sensitive to a variety of insults. Epidemiological studies have identified prenatal exposure to infection as a risk factor for a range of neurological disorders, including autism spectrum disorder and schizophrenia. Animal models corroborate this association and have been used to probe the contribution of gene-environment interactions to the etiology of neurodevelopmental disorders. Here we review the behavior and brain phenotypes that have been characterized in MIA offspring, including the studies that have looked at the interaction between maternal immune activation and genetic risk factors for autism spectrum disorder or schizophrenia. These phenotypes include behaviors relevant to autism, schizophrenia, and other neurological disorders, alterations in brain anatomy, and structural and functional neuronal impairments. The link between maternal infection and these phenotypic changes is not fully understood, but there is increasing evidence that maternal immune activation induces prolonged immune alterations in the offspring's brain which could underlie epigenetic alterations which in turn may mediate the behavior and brain changes. These concepts will be discussed followed by a summary of the pharmacological interventions that have been tested in the maternal immune activation model.

Maternal prenatal depression predicts infant negative affect via maternal inflammatory cytokine levels

Maternal depressive symptoms during pregnancy are associated with risk for offspring emotional and behavioral problems, but the mechanisms by which this association occurs are not known. Infant elevated negative affect (increased crying, irritability, fearfulness, etc.) is a key risk factor for future psychopathology, so understanding its determinants has prevention and early intervention potential. An understudied yet promising hypothesis is that maternal mood affects infant mood via maternal prenatal inflammatory mechanisms, but this has not been prospectively examined in humans. Using data from a pilot study of women followed from the second trimester of pregnancy through six months postpartum (N = 68) our goal was to initiate a prospective study as to whether maternal inflammatory cytokines mediate the association between maternal depressive symptoms and infant offspring negative affect. The study sample was designed to examine a broad range of likely self-regulation and mood-regulation problems in offspring; to that end we over-selected women with a family history or their own history of elevated symptoms of attention-deficit/hyperactivity disorder. Results supported the hypothesis: maternal pro-inflammatory cytokines during the third trimester (indexed using a latent variable that included plasma interleukin-6, tumor necrosis factor-alpha and monocyte chemoattractant protein-1 concentrations as indicators) mediated the effect, such that higher maternal depressive symptoms were associated with higher maternal inflammation, and this mediated the effect on maternal report of infant negative affect (controlling for maternal affect during the infant period). This is the first human study to demonstrate that maternal inflammatory cytokines mediate the association between prenatal depression and infant outcomes, and the first to demonstrate a biological mechanism through which depressive symptoms impact infant temperament.

Active HHV-6 Infection of Cerebellar Purkinje Cells in Mood Disorders

Early-life infections and associated neuroinflammation is incriminated in the pathogenesis of various mood disorders. Infection with human roseoloviruses, HHV-6A and HHV-6B, allows viral latency in the central nervous system and other tissues, which can later be activated causing cognitive and behavioral disturbances. Hence, this study was designed to evaluate possible association of HHV-6A and HHV-6B activation with three different groups of psychiatric patients. DNA qPCR, immunofluorescence and FISH studies were carried out in post-mortem posterior cerebellum from 50 cases each of bipolar disorder (BPD), schizophrenia, 15 major depressive disorder (MDD) and 50 appropriate control samples obtained from two well-known brain collections (Stanley Medical Research Institute). HHV-6A and HHV-6B late proteins (indicating active infection) and viral DNA were detected more frequently (p < 0.001 for each virus) in human cerebellum in MDD and BPD relative to controls. These roseolovirus proteins and DNA were found less frequently in schizophrenia cases. Active HHV-6A and HHV-6B infection in cerebellar Purkinje cells were detected frequently in BPD and MDD cases. Furthermore, we found a significant association of HHV-6A infection with reduced Purkinje cell size, suggesting virus-mediated abnormal Purkinje cell function in these disorders. Finally, gene expression analysis of cerebellar tissue revealed changes in pathways reflecting an inflammatory response possibly to HHV-6A infection. Our results provide molecular evidence to support a role for active HHV-6A and HHV-6B infection in BPD and MDD.

Maternal Immune Activation Delays Excitatory-to-Inhibitory Gamma-Aminobutyric Acid Switch in Offspring

BACKGROUND

The association between maternal infection and neurodevelopmental defects in progeny is well established, although the biological mechanisms and the pathogenic trajectories involved have not been defined.

METHODS

Pregnant dams were injected intraperitoneally at gestational day 9 with polyinosinic:polycytidylic acid. Neuronal development was assessed by means of electrophysiological, optical, and biochemical analyses.

RESULTS

Prenatal exposure to polyinosinic:polycytidylic acid causes an imbalanced expression of the Na+-K+-2Cl- cotransporter 1 and the K+-Cl- cotransporter 2 (KCC2). This results in delayed gamma-aminobutyric acid switch and higher susceptibility to seizures, which endures up to adulthood. Chromatin immunoprecipitation experiments reveal increased binding of the repressor factor RE1-silencing transcription (also known as neuron-restrictive silencer factor) to position 509 of the KCC2 promoter that leads to downregulation of KCC2 transcription in prenatally exposed offspring. Interleukin-1 receptor type I knockout mice, which display braked immune response and no brain cytokine elevation upon maternal immune activation, do not display KCC2/Na+-K+-2Cl- cotransporter 1 imbalance when implanted in a wild-type dam and prenatally exposed. Notably, pretreatment of pregnant dams with magnesium sulfate is sufficient to prevent the early inflammatory state and the delay in excitatory-to-inhibitory switch associated to maternal immune activation.

CONCLUSIONS

We provide evidence that maternal immune activation hits a key neurodevelopmental process, the excitatory-to-inhibitory gamma-aminobutyric acid switch; defects in this switch have been unequivocally linked to diseases such as autism spectrum disorder or epilepsy. These data open the avenue for a safe pharmacological treatment that may prevent the neurodevelopmental defects caused by prenatal immune activation in a specific pregnancy time window.

Maternal immune activation in neurodevelopmental disorders

Converging lines of evidence from basic science and clinical studies suggest a relationship between maternal immune activation (MIA) and neurodevelopmental disorders such as autism spectrum disorder (ASD) and schizophrenia. The mechanisms through which MIA increases the risk of neurodevelopmental disorders have become a subject of intensive research. This review aims to describe how dysregulation of microglial function and immune mechanisms may link MIA and neurodevelopmental pathologies. We also summarize the current evidence in animal models of MIA. Developmental Dynamics 247:588-619, 2018. © 2017 Wiley Periodicals, Inc.

Activation of EP2 receptor suppresses poly(I: C) and LPS-mediated inflammation in primary microglia and organotypic hippocampal slice cultures: Contributing role for MAPKs

Brain inflammation is a critical factor involved in neurodegeneration. Recently, the prostaglandin E₂ (PGE₂ ) downstream members were suggested to modulate neuroinflammatory responses accompanying neurodegenerative diseases. In this study, we investigated the protective effects of prostaglandin E₂ receptor 2 (EP₂ ) during TLR3 and TLR4-driven inflammatory response using in vitro primary microglia and ex vivo organotypic hippocampal slice cultures (OHSCs). Depletion of microglia from OHSCs differentially affected TLR3 and TLR4 receptor expression. Poly(I:C) induced the production of prostaglandin E₂ in OHSCs by increasing cyclooxygenase (COX-2) and microsomal prostaglandin E synthase (mPGES)-1. Besides, stimulation of OHSCs and microglia with Poly(I:C) upregulated EP₂ receptor expression. Co-stimulation of OHSCs and microglia with the EP₂ agonist butaprost reduced inflammatory mediators induced by LPS and Poly(I:C). In Poly(I:C) challenged OHSCs, butaprost almost restored microglia ramified morphology and reduced Iba1 immunoreactivity. Importantly, microglia depletion prevented the induction of inflammatory mediators following Poly(I:C) or LPS challenge in OHSCs. Activation of EP₂ receptor reversed the Poly(I:C)/LPS-induced phosphorylation of the mitogen activated protein kinases (MAPKs) ERK, p38 MAPK and c-Jun N-terminal kinase (JNK) in microglia. Collectively, these data identify an anti-inflammatory function for EP₂ signaling in diverse innate immune responses, through a mechanism that involves the mitogen-activated protein kinases pathway.