Maternal infection and fever during late gestation are associated with altered synaptic transmission in the hippocampus of juvenile offspring rats

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

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

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

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

Maternal Immune Activation Affects Hippocampal Excitatory and Inhibitory Synaptic Transmission in Offspring From an Early Developmental Period to Adulthood

One of the risk factors for schizophrenia is maternal infection. We have previously shown that Polyriboinosinic-polyribocytidylic acid (poly I:C) induced maternal immune activation in mice caused histological changes in the hippocampal CA1 area of offspring during the developmental period and impaired sensorimotor gating in offspring during adulthood, resulting in behavioral changes. However, it remains unclear how maternal immune activation functionally impacts the hippocampal neuronal activity of offspring. We studied the effect of prenatal poly I:C treatment on synaptic transmission of hippocampal CA1 pyramidal cells in postnatal and adult offspring. Treatment with poly I:C diminished excitatory and enhanced inhibitory (GABAergic) synaptic transmission on pyramidal cells in adult offspring. During the early developmental period, we still observed that treatment with poly I:C decreased excitatory synaptic transmission and potentially increased GABAergic synaptic transmission, which was uncovered under a condition of high extracellular potassium-activated neurons. In conclusion, we demonstrate that maternal immune activation decreased excitatory and increased inhibitory synaptic transmission on hippocampal pyramidal cells from an early developmental period to adulthood, which could result in net inhibition in conjunction with poor functional organization and integration of hippocampal circuits.

A Systematic Review of Magnesium Sulfate for Perinatal Neuroprotection: What Have We Learnt From the Past Decade?

There is an important unmet need to improve long term outcomes of encephalopathy for preterm and term infants. Meta-analyses of large controlled trials suggest that maternal treatment with magnesium sulfate (MgSO₄) is associated with a reduced risk of cerebral palsy and gross motor dysfunction after premature birth. However, to date, follow up to school age has found an apparent lack of long-term clinical benefit. Because of this inconsistency, it remains controversial whether MgSO₄ offers sustained neuroprotection. We systematically reviewed preclinical and clinical studies reported from January 1 2010, to January 31 2020 to evaluate the most recent advances and knowledge gaps relating to the efficacy of MgSO₄ for the treatment of perinatal brain injury. The outcomes of MgSO₄ in preterm and term-equivalent animal models of perinatal encephalopathy were highly inconsistent between studies. None of the perinatal rodent studies that suggested benefit directly controlled body or brain temperature. The majority of the studies did not control for sex, study long term histological and functional outcomes or use pragmatic treatment regimens and many did not report controlling for potential study bias. Finally, most of the recent preterm or term human studies that tested the potential of MgSO₄ for perinatal neuroprotection were relatively underpowered, but nevertheless, suggest that any improvements in neurodevelopment were at best modest or absent. On balance, these data suggest that further rigorous testing in translational preclinical models of perinatal encephalopathy is essential to ensure safety and best regimens for optimal preterm neuroprotection, and before further clinical trials of MgSO₄ for perinatal encephalopathy at term are undertaken.

Lipopolysaccharide exposure during late embryogenesis triggers and drives Alzheimer-like behavioral and neuropathological changes in CD-1 mice

INTRODUCTION

Infections could contribute to Alzheimer's disease (AD) neuropathology in human. However, experimental evidence for a causal relationship between infections during the prenatal phase and the onset of AD is lacking.

METHODS

CD-1 mothers were intraperitoneally received lipopolysaccharide (LPS) with two doses (25 and 50 μg/kg) or normal saline every day during gestational days 15-17. A battery of behavioral tasks was used to assess the species-typical behavior, sensorimotor capacity, anxiety, locomotor activity, recognition memory, and spatial learning and memory in 1-, 6-, 12-, 18-, and 22-month-old offspring mice. An immunohistochemical technology was performed to detect neuropathological indicators consisting of amyloid-β (Aβ), phosphorylated tau (p-tau), and glial fibrillary acidic protein (GFAP) in the hippocampus.

RESULTS

Compared to the same-aged controls, LPS-treated offspring had similar behavioral abilities and the levels of Aβ42, p-tau, and GFAP at 1 and 6 months old. From 12 months onward, LPS-treated offspring gradually showed decreased species-typical behavior, sensorimotor ability, locomotor activity, recognition memory, and spatial learning and memory, and increased anxieties and the levels of Aβ42, p-tau, and GFAP relative to the same-aged controls. Moreover, this damage effect (especially cognitive decline) persistently progressed onwards. The changes in these neuropathological indicators significantly correlated with impaired spatial learning and memory.

CONCLUSIONS

Prenatal exposure to low doses of LPS caused AD-related features including behavioral and neuropathological changes from midlife to senectitude.

Effects of inflammation on the developing respiratory system: Focus on hypoglossal (XII) neuron morphology, brainstem neurochemistry, and control of breathing

Breathing is fundamental to life and any adverse change in respiratory function can endanger the health of an organism or even be fatal. Perinatal inflammation is known to adversely affect breathing in preterm babies, but lung infection/inflammation impacts all stages of life from birth to death. Little is known about the role of inflammation in respiratory control, neuronal morphology, or neural function during development. Animal models of inflammation can provide understanding and insight into respiratory development and how inflammatory processes alter developmental phenotype in addition to providing insight into new treatment modalities. In this review, we focus on recent work concerning the development of neurons, models of perinatal inflammation with an emphasis on two common LPS-based models, inflammation and its impact on development, and current and potential treatments for inflammation within the respiratory control circuitry of the mammalian brainstem. We have also discussed models of inflammation in adults and have specifically focused on hypoglossal motoneurons (XII) and neurons of the nucleus tractus solitarii (nTS) as these nuclei have been studied more extensively than other brainstem nuclei participating in breathing and airway control. Understanding the impact of inflammation on the developmental aspects of respiratory control and breathing pattern is critical to addressing problems of cardiorespiratory dysregulation in disease and this overview points out many gaps in our current knowledge.

Neuroimmunology of the female brain across the lifespan: Plasticity to psychopathology

The female brain is highly dynamic and can fundamentally remodel throughout the normal ovarian cycle as well as in critical life stages including perinatal development, pregnancy and old-age. As such, females are particularly vulnerable to infections, psychological disorders, certain cancers, and cognitive impairments. We will present the latest evidence on the female brain; how it develops through the neonatal period; how it changes through the ovarian cycle in normal individuals; how it adapts to pregnancy and postpartum; how it responds to illness and disease, particularly cancer; and, finally, how it is shaped by old age. Throughout, we will highlight female vulnerability to and resilience against disease and dysfunction in the face of environmental challenges.

Maternal immune activation-induced PPARγ-dependent dysfunction of microglia associated with neurogenic impairment and aberrant postnatal behaviors in offspring

Maternal infection during pregnancy is an important factor involved in the pathogenesis of brain disorders in the offspring. Mounting evidence from maternal immune activation (MIA) animals indicates that microglial priming may contribute to neurodevelopmental abnormalities in the offspring. Because peroxisome proliferator-activated receptor gamma (PPARγ) activation exerts neuroprotective effects by regulating neuroinflammatory response, it is a pharmacological target for treating neurogenic disorders. We investigated the effect of PPARγ-dependent microglial activation on neurogenesis and consequent behavioral outcomes in male MIA-offspring. Pregnant dams on gestation day 18 received Poly(I:C) (1, 5, or 10 mg/kg; i.p.) or the vehicle. The MIA model that received 10 mg/kg Poly(I:C) showed significantly increased inflammatory responses in the maternal serum and fetal hippocampus, followed by cognitive deficits, which were highly correlated with hippocampal neurogenesis impairment in prepubertal male offspring. The microglial population in hippocampus increased, displayed decreased processes and larger soma, and had a higher expression of the CD11b, which is indicative of the M1 phenotype (classical activation). Activation of the PPARγ pathway by pioglitazone in the MIA offspring rescued the imbalance of the microglial activation and ameliorated the MIA-induced suppressed neurogenesis and cognitive impairments and anxiety behaviors. In an in vitro experiment, PPARγ-induced M2 microglia (alternative activation) promoted the proliferation and differentiation of neural precursor cells. These results indicated that the MIA-induced long-term changes in microglia phenotypes were associated with hippocampal neurogenesis and neurobehavioral abnormalities in offspring. Modulation of the microglial phenotypes was associated with a PPARγ-mediated neuroprotective mechanism in the MIA offspring and may serve as a potential therapeutic approach for prenatal immune activation-induced neuropsychiatric disorders.

Dietary omega-3 deficiency exacerbates inflammation and reveals spatial memory deficits in mice exposed to lipopolysaccharide during gestation

Maternal immune activation (MIA) is a common environmental insult on the developing brain and represents a risk factor for neurodevelopmental disorders. Animal models of in utero inflammation further revealed a causal link between maternal inflammatory activation during pregnancy and behavioural impairment relevant to neurodevelopmental disorders in the offspring. Accumulating evidence point out that proinflammatory cytokines produced both in the maternal and fetal compartments are responsible for social, cognitive and emotional behavioral deficits in the offspring. Polyunsaturated fatty acids (PUFAs) are essential fatty acids with potent immunomodulatory activities. PUFAs and their bioactive derivatives can promote or inhibit many aspects of the immune and inflammatory response. PUFAs of the n-3 series ('n-3 PUFAs', also known as omega-3) exhibit anti-inflammatory/pro-resolution properties and promote immune functions, while PUFAs of the n-6 series ('n-6 PUFAs' or omega-6) favor pro-inflammatory responses. The present study aimed at providing insight into the effects of n-3 PUFAs on the consequences of MIA on brain development. We hypothesized that a reduction in n-3 PUFAs exacerbates both maternal and fetal inflammatory responses to MIA and later-life defects in memory in the offspring. Based on a lipopolysaccharide (LPS) model of MIA (LPS injection at embryonic day 17), we showed that n-3 PUFA deficiency 1) alters fatty acid composition of the fetal and adult offspring brain; 2) exacerbates maternal and fetal inflammatory processes with no significant alteration of microglia phenotype, and 3) induces spatial memory deficits in the adult offspring. We also showed a strong negative correlation between brain content in n-3 PUFA and cytokine production in MIA-exposed fetuses. Overall, our study is the first to address the deleterious effects of n-3 PUFA deficiency on brain lipid composition, inflammation and memory performances in MIA-exposed animals and indicates that it should be considered as a potent environmental risk factor for the apparition of neurodevelopmental disorders.

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.

Chorioamnionitis, IL-17A, and fetal origins of neurologic disease

The Centers for Disease Control and Prevention estimate that 1 in 323 infants have cerebral palsy. Highly correlated to intrauterine infection and inflammation, the incidence of cerebral palsy has remained constant over the last few decades despite significant advances in neonatal intensive care including improved ventilator techniques, surfactant therapy, maternal steroid administration, and use of intrapartum empiric antimicrobials. Recent advances in our understanding of immune responses to infection and inflammation have identified the cytokine IL-17A as a crucial component of early proinflammatory mediators that cause brain injury associated with neurologic impairment. Remarkably, maternal inflammatory responses to in utero inflammation and infection can also lead to potentially debilitating neurologic conditions in the offspring, which often become clinically apparent during childhood and/or early adulthood. This review details the role of IL-17A in fetal and maternal proinflammatory responses that lead to fetal brain injury and neurologic sequelae, including cerebral palsy. Recent findings regarding the role of maternal inflammatory responses in the development of childhood and adult neurologic conditions, such as autism, schizophrenia, and multiple sclerosis, will also be highlighted.

Tumour necrosis factor-mediated homeostatic synaptic plasticity in behavioural models: testing a role in maternal immune activation

The proinflammatory cytokine tumour necrosis factor-alpha (TNFα) has long been characterized for its role in the innate immune system, but more recently has been found to have a distinct role in the nervous system that does not overlap with other proinflammatory cytokines. Through regulation of neuronal glutamate and GABA receptor trafficking, TNF mediates a homeostatic form of synaptic plasticity, but plays no direct role in Hebbian forms of plasticity. As yet, there is no evidence to suggest that this adaptive plasticity plays a significant role in normal development, but it does maintain neuronal circuit function in the face of several types of disruption. This includes developmental plasticity in primary sensory cortices, as well as modulating the response to antidepressants, chronic antipsychotics and drugs of abuse. TNF is also a prominent component of the neuroinflammation occurring in most neuropathologies, but the role of TNF-mediated synaptic plasticity in this context remains to be determined. We tested this in a maternal immune activation (MIA) model of neurodevelopmental disorders. Using TNF^-/- mice, we observed that TNF is not required for the expression of abnormal social or anxious behaviour in this model. This indicates that TNF does not uniquely contribute to the development of neuronal dysfunction in this model, and suggests that during neuroinflammatory events, compensation between the various proinflammatory cytokines is the norm.This article is part of the themed issue 'Integrating Hebbian and homeostatic plasticity'.

Sex-specific gene-environment interactions underlying ASD-like behaviors

The male bias in the incidence of autism spectrum disorders (ASDs) is one of the most notable characteristics of this group of neurodevelopmental disorders. The etiology of this sex bias is far from known, but pivotal for understanding the etiology of ASDs in general. Here we investigate whether a "three-hit" (genetic load × environmental factor × sex) theory of autism may help explain the male predominance. We found that LPS-induced maternal immune activation caused male-specific deficits in certain social responses in the contactin-associated protein-like 2 (Cntnap2) mouse model for ASD. The three "hits" had cumulative effects on ultrasonic vocalizations at postnatal day 3. Hits synergistically affected social recognition in adulthood: only mice exposed to all three hits showed deficits in this aspect of social behavior. In brains of the same mice we found a significant three-way interaction on corticotropin-releasing hormone receptor-1 (Crhr1) gene expression, in the left hippocampus specifically, which co-occurred with epigenetic alterations in histone H3 N-terminal lysine 4 trimethylation (H3K4me3) over the Crhr1 promoter. Although it is highly likely that multiple (synergistic) interactions may be at work, change in the expression of genes in the hypothalamic-pituitary-adrenal/stress system (e.g., Crhr1) is one of them. The data provide proof-of-principle that genetic and environmental factors interact to cause sex-specific effects that may help explain the male bias in ASD incidence.

Blood borne: bacterial components in mother's blood influence fetal development

Bacterial or viral infection of the mother during the course of pregnancy can cross the placenta and actively infect the fetus. However, especially for bacteria, it is more common for mothers to experience an infection that can be treated without overt fetal infection. In this setting, it is less well understood what the risk to fetal development is, particularly in terms of neurological development. This research highlight reviews recent findings indicating that bacterial components generated during infection of the mother can cross the placenta and activate the fetal innate immune system resulting in changes in the course of brain development and subsequent progression to postnatal cognitive disorders. Bacterial cell wall is a ubiquitous bacterial PAMP (pathogen-associated molecular pattern) known to activate inflammation through the stimulation of TLR2. Cell wall is released from bacteria during antibiotic treatment and new work shows that embryos exposed to cell wall from the mother demonstrate anomalous proliferation of neuronal precursor cells in a TLR2 dependent manner. Such proliferation increases the neuronal density of the cortical plate and alters brain architecture. Although there is no fetal death, subsequent cognitive development is significantly impaired. This model system suggests that bacterial infection of the mother and its treatment can impact fetal brain development and requires greater understanding to potentially eliminate a risk factor for cognitive disorders such as autism.

Environmental enrichment rescues the effects of early life inflammation on markers of synaptic transmission and plasticity

Environmental enrichment (EE) has been successful at rescuing the brain from a variety of early-life psychogenic stressors. However, its ability to reverse the behavioral and neural alterations induced by a prenatal maternal infection model of schizophrenia is less clear. Moreover, the specific interactions between the components (i.e. social enhancement, novelty, physical activity) of EE that lead to its success as a supportive intervention have not been adequately identified. In the current study, standard housed female Sprague-Dawley rats were administered either the inflammatory endotoxin lipopolysaccharide (LPS; 100μg/kg) or pyrogen-free saline (equivolume) on gestational day 15. On postnatal day 50, offspring were randomized into one of three conditions: EE (group housed in a large multi-level cage with novel toys, tubes and ramps), Colony Nesting (CN; socially-housed in a larger style cage), or Standard Care (SC; pair-housed in standard cages). Six weeks later we scored social engagement and performance in the object-in-place task. Afterwards hippocampus and prefrontal cortex (n=7-9) were collected and evaluated for excitatory amino acid transporter (EAAT) 1-3, brain-derived neurotrophic factor (BDNF), and neurotrophic tyrosine kinase, receptor type 2 (TrkB) gene expression (normalized to GAPDH) using qPCR methods. Overall, we show that gestational inflammation downregulates genes critical to synaptic transmission and plasticity, which may underlie the pathogenesis of neurodevelopmental disorders such as schizophrenia and autism. Additionally, we observed disruptions in both social engagement and spatial discrimination. Importantly, behavioral and neurophysiological effects were rescued in an experience dependent manner. Given the evidence that schizophrenia and autism may be associated with infection during pregnancy, these data have compelling implications for the prevention and reversibility of the consequences that follow immune activation in early in life.

Bacterial Peptidoglycan Traverses the Placenta to Induce Fetal Neuroproliferation and Aberrant Postnatal Behavior

Maternal infection during pregnancy is associated with adverse outcomes for the fetus, including postnatal cognitive disorders. However, the underlying mechanisms are obscure. We find that bacterial cell wall peptidoglycan (CW), a universal PAMP for TLR2, traverses the murine placenta into the developing fetal brain. In contrast to adults, CW-exposed fetal brains did not show any signs of inflammation or neuronal death. Instead, the neuronal transcription factor FoxG1 was induced, and neuroproliferation leading to a 50% greater density of neurons in the cortical plate was observed. Bacterial infection of pregnant dams, followed by antibiotic treatment, which releases CW, yielded the same result. Neuroproliferation required TLR2 and was recapitulated in vitro with fetal neuronal precursor cells and TLR2/6, but not TLR2/1, ligands. The fetal neuroproliferative response correlated with abnormal cognitive behavior in CW-exposed pups following birth. Thus, the bacterial CW-TLR2 signaling axis affects fetal neurodevelopment and may underlie postnatal cognitive disorders.

Maternal immune activation alters glutamic acid decarboxylase-67 expression in the brains of adult rat offspring

Activation of the maternal innate immune system, termed "maternal immune activation" (MIA), represents a common environmental risk factor for schizophrenia. Whereas evidence suggests dysregulation of GABA systems may underlie the pathophysiology of schizophrenia, a role for MIA in alteration of GABAergic systems is less clear. Here, pregnant rats received either the viral mimetic polyriboinosinic-polyribocytidilic acid or vehicle injection on gestational day 14. Glutamic acid decarboxylase-67 (GAD67) mRNA expression was examined in male offspring at postnatal day (P)14, P30 and P60. At P60, GAD67 mRNA was elevated in hippocampus and thalamus and decreased in prefrontal cortex of MIA offspring. MIA-induced alterations in GAD expression could contribute to the pathophysiology of schizophrenia.

Maternal immune activation produces neonatal excitability defects in offspring hippocampal neurons from pregnant rats treated with poly I:C

Maternal immune activation (MIA) resulting from prenatal exposure to infectious pathogens or inflammatory stimuli is increasingly recognized to play an important etiological role in neuropsychiatric disorders with neurodevelopmental features. MIA in pregnant rodents induced by injection of the synthetic double-stranded RNA, Poly I:C, a mimic of viral infection, leads to a wide spectrum of behavioral abnormalities as well as structural and functional defects in the brain. Previous MIA studies using poly I:C prenatal treatment suggested that neurophysiological alterations occur in the hippocampus. However, these investigations used only juvenile or adult animals. We postulated that MIA-induced alterations could occur earlier at neonatal/early postnatal stages. Here we examined the neurophysiological properties of cultured pyramidal-like hippocampal neurons prepared from neonatal (P0-P2) offspring of pregnant rats injected with poly I:C. Offspring neurons from poly I:C-treated mothers exhibited significantly lower intrinsic excitability and stronger spike frequency adaptation, compared to saline. A similar lower intrinsic excitability was observed in CA1 pyramidal neurons from hippocampal slices of two weeks-old poly I:C offspring. Cultured hippocampal neurons also displayed lower frequency of spontaneous firing, higher charge transfer of IPSCs and larger amplitude of miniature IPSCs. Thus, maternal immune activation leads to strikingly early neurophysiological abnormalities in hippocampal neurons.

Disrupted Circadian Rhythm as a Common Player in Developmental Models of Neuropsychiatric Disorders

The environment in which individuals develop and mature is critical for their physiological and psychological outcome; in particular, the intrauterine environment has reached far more clinical relevance given its potential influence on shaping brain function and thus mental health. Gestational stress and/or maternal infection during pregnancy has been related with an increased incidence of neuropsychiatric disorders, including depression and schizophrenia. In this framework, the use of animal models has allowed a formal and deep investigation of causal determinants. Despite disruption of circadian clocks often represents a hallmark of several neuropsychiatric disorders, the relationship between disruption of brain development and the circadian system has been scarcely investigated. Nowadays, there is an increasing amount of studies suggesting a link between circadian system malfunction, early-life insults and the appearance of neuropsychiatric diseases at adulthood. Here, we briefly review evidence from clinical literature and animal models suggesting that the exposure to prenatal insults, i.e. severe gestational stress or maternal immune activation, changes the foetal hormonal milieu increasing the circulating levels of both glucocorticoids and pro-inflammatory cytokines. These two biological events have been reported to affect genes expression in experimental models and critically interfere with brain development triggering and/or exacerbating behavioural anomalies in the offspring. Herein, we highlight the importance to unravel the individual components of the body circadian system that might also be altered by prenatal insults and that may be causally associated with the disruption of neural and endocrine developmental programming.

Maturation- and sex-sensitive depression of hippocampal excitatory transmission in a rat schizophrenia model

Schizophrenia is associated with behavioral and brain structural abnormalities, of which the hippocampus appears to be one of the most consistent region affected. Previous studies performed on the poly I:C model of schizophrenia suggest that alterations in hippocampal synaptic transmission and plasticity take place in the offspring. However, these investigations yielded conflicting results and the neurophysiological alterations responsible for these deficits are still unclear. Here we performed for the first time a longitudinal study examining the impact of prenatal poly I:C treatment and of gender on hippocampal excitatory neurotransmission. In addition, we examined the potential preventive/curative effects of risperidone (RIS) treatment during the peri-adolescence period. Excitatory synaptic transmission was determined by stimulating Schaffer collaterals and monitoring fiber volley amplitude and slope of field-EPSP (fEPSP) in CA1 pyramidal neurons in male and female offspring hippocampal slices from postnatal days (PNDs) 18-20, 34, 70 and 90. Depression of hippocampal excitatory transmission appeared at juvenile age in male offspring of the poly I:C group, while it expressed with a delay in female, manifesting at adulthood. In addition, a reduced hippocampal size was found in both adult male and female offspring of poly I:C treated dams. Treatment with RIS at the peri-adolescence period fully restored in males but partly repaired in females these deficiencies. A maturation- and sex-dependent decrease in hippocampal excitatory transmission occurs in the offspring of poly I:C treated pregnant mothers. Pharmacological intervention with RIS during peri-adolescence can cure in a gender-sensitive fashion early occurring hippocampal synaptic deficits.

Maternal immune activation evoked by polyinosinic:polycytidylic acid does not evoke microglial cell activation in the embryo

Several studies have indicated that inflammation during pregnancy increases the risk for the development of neuropsychiatric disorders in the offspring. Morphological brain abnormalities combined with deviations in the inflammatory status of the brain can be observed in patients of both autism and schizophrenia. It was shown that acute infection can induce changes in maternal cytokine levels which in turn are suggested to affect fetal brain development and increase the risk on the development of neuropsychiatric disorders in the offspring. Animal models of maternal immune activation reproduce the etiology of neurodevelopmental disorders such as schizophrenia and autism. In this study the poly (I:C) model was used to mimic viral immune activation in pregnant mice in order to assess the activation status of fetal microglia in these developmental disorders. Because microglia are the resident immune cells of the brain they were expected to be activated due to the inflammatory stimulus. Microglial cell density and activation level in the fetal cortex and hippocampus were determined. Despite the presence of a systemic inflammation in the pregnant mice, there was no significant difference in fetal microglial cell density or immunohistochemically determined activation level between the control and inflammation group. These data indicate that activation of the fetal microglial cells is not likely to be responsible for the inflammation induced deficits in the offspring in this model.

Mechanisms of fever production and lysis: lessons from experimental LPS fever

Fever is a cardinal symptom of infectious or inflammatory insults, but it can also arise from noninfectious causes. The fever-inducing agent that has been used most frequently in experimental studies designed to characterize the physiological, immunological and neuroendocrine processes and to identify the neuronal circuits that underlie the manifestation of the febrile response is lipopolysaccharide (LPS). Our knowledge of the mechanisms of fever production and lysis is largely based on this model. Fever is usually initiated in the periphery of the challenged host by the immediate activation of the innate immune system by LPS, specifically of the complement (C) cascade and Toll-like receptors. The first results in the immediate generation of the C component C5a and the subsequent rapid production of prostaglandin E2 (PGE2). The second, occurring after some delay, induces the further production of PGE2 by induction of its synthesizing enzymes and transcription and translation of proinflammatory cytokines. The Kupffer cells (Kc) of the liver seem to be essential for these initial processes. The subsequent transfer of the pyrogenic message from the periphery to the brain is achieved by neuronal and humoral mechanisms. These pathways subserve the genesis of early (neuronal signals) and late (humoral signals) phases of the characteristically biphasic febrile response to LPS. During the course of fever, counterinflammatory factors, "endogenous antipyretics," are elaborated peripherally and centrally to limit fever in strength and duration. The multiple interacting pro- and antipyretic signals and their mechanistic effects that underlie endotoxic fever are the subjects of this review.

Aberrant NMDA-dependent LTD after perinatal ethanol exposure in young adult rat hippocampus

Irreversible cognitive deficits induced by ethanol exposure during fetal life have been ascribed to a lower NMDA-dependent synaptic long-term potentiation (LTP) in the hippocampus. Whether NMDA-dependent long-term depression (LTD) may also play a critical role in those deficits remains unknown. Here, we show that in vitro LTD induced with paired-pulse low frequency stimulation is enhanced in CA1 hippocampus field of young adult rats exposed to ethanol during brain development. Furthermore, single pulse low frequency stimulation, ineffective at this age (LFS600), induced LTD after ethanol exposure accompanied with a stronger response than controls during LFS600, thus revealing an aberrant form of activity-dependent plasticity at this age. Blocking NMDA receptor or GluN2B containing NMDA receptor prevented both the stronger response during LFS600 and LTD whereas Zinc, an antagonist of GluN2A containing NMDA receptor, was ineffective on both responses. In addition, LFS600-induced LTD was revealed in controls only with a reduced-Mg(2+) medium. In whole dissected hippocampus CA1 field, perinatal ethanol exposure increased GluN2B subunit expression in the synaptic compartment whereas GluN2A was unaltered. Using pharmacological tools, we suggest that LFS600 LTD was of synaptic origin. Altogether, we describe a new mechanism by which ethanol exposure during fetal life induces a long-term alteration of synaptic plasticity involving NMDA receptors, leading to an aberrant LTD. We suggest this effect of ethanol may reflect a delayed maturation of the synapse and that aberrant LTD may also participates to long-lasting cognitive deficits in fetal alcohol spectrum disorder.

Toward an immune-mediated subtype of autism spectrum disorder

A role for immunological involvement in autism spectrum disorder (ASD) has long been hypothesized. This review includes four sections describing (1) evidence for a relationship between familial autoimmune disorders and ASD; (2) results from post-mortem and neuroimaging studies that investigated aspects of neuroinflammation in ASD; (3) findings from animal model work in ASD involving inflammatory processes; and (4) outcomes from trials of anti-inflammatory/immune-modulating drugs in ASD that have appeared in the literature. Following each section, ideas are provided for future research, suggesting paths forward in the continuing effort to define the role of immune factors and inflammation in the pathophysiology of a subtype of ASD. This article is part of a Special Issue entitled SI: Neuroimmunology in Health And Disease.

Effect of sustained postnatal systemic inflammation on hippocampal volume and function in mice

BACKGROUND

Premature infants are at risk for persistent neurodevelopmental impairment. Children born preterm often exhibit reduced hippocampal volumes that correlate with deficits in working memory. Perinatal inflammation is associated with preterm birth and brain abnormalities. Here we examine the effects of postnatal systemic inflammation on the developing hippocampus in mice.

METHODS

Pups received daily intraperitoneal injections of lipopolysaccharide (LPS) or saline between days 3 and 13. Ex vivo magnetic resonance imaging (MRI) and microscopic analysis of brain tissue was performed on day 14. Behavioral testing was conducted at 8-9 wk of age.

RESULTS

MR and microscopic analysis revealed a 15-20% reduction in hippocampal volume in LPS-treated mice compared with controls. Behavioral testing revealed deficits in hippocampal-related tasks in LPS-treated animals. Adult mice exposed to LPS during the postnatal period were unable to select a novel environment when re-placed within a 1-min delay, were less able to remember a familiar object after a 1-h delay, and had impaired retention of associative fear learning after 24 h.

CONCLUSION

Systemic inflammation sustained during the postnatal period contributes to reduced hippocampal volume and deficits in hippocampus-dependent working memory. These findings support the novel and emerging concept that sustained systemic inflammation contributes to neurodevelopmental impairment among preterm infants.

Relationship between Interleukin-6 gene polymorphism and hippocampal volume in antipsychotic-naïve schizophrenia: evidence for differential susceptibility?

Background

Various lines of evidence including epidemiological, genetic and foetal pathogenetic models suggest a compelling role for Interleukin-6 (IL-6) in the pathogenesis of schizophrenia. IL-6 mediated inflammatory response triggered by maternal infection or stress induces disruption of prenatal hippocampal development which might contribute towards psychopathology during adulthood. There is a substantial lack of knowledge on how genetic predisposition to elevated IL-6 expression effects hippocampal structure in schizophrenia patients. In this first-time study, we evaluated the relationship between functional polymorphism rs1800795 of IL-6 and hippocampal gray matter volume in antipsychotic-naïve schizophrenia patients in comparison with healthy controls.

Methodology

We examined antipsychotic-naïve schizophrenia patients [N = 28] in comparison with healthy controls [N = 37] group matched on age, sex and handedness. Using 3 Tesla – MRI, bilateral hippocampi were manually segmented by blinded raters with good inter-rater reliability using a valid method. Additionally, Voxel-based Morphometry (VBM) analysis was performed using hippocampal mask. The IL-6 level was measured in blood plasma using ELISA technique. SNP rs1800795 was genotyped using PCR and DNA sequencing. Psychotic symptoms were assessed using Scale for Assessment of Positive Symptoms and Scale for Assessment of Negative Symptoms.

Results

Schizophrenia patients had significantly deficient left and right hippocampal volumes after controlling for the potential confounding effects of age, sex and total brain volume. Plasma IL-6 levels were significantly higher in patients than controls. There was a significant diagnosis by rs1800795 genotype interaction involving both right and left hippocampal volumes. Interestingly, this effect was significant only in men but not in women.

Conclusion

Our first time observations suggest a significant relationship between IL-6 rs1800795 and reduced hippocampal volume in antipsychotic-naïve schizophrenia. Moreover, this relationship was antithetical in healthy controls and this effect was observed in men but not in women. Together, these observations support a “differential susceptibility” effect of rs1800795 in schizophrenia pathogenesis mediated through hippocampal volume deficit that is of possible neurodevelopmental origin.

Heat shock alters the expression of schizophrenia and autism candidate genes in an induced pluripotent stem cell model of the human telencephalon

Schizophrenia (SZ) and autism spectrum disorders (ASD) are highly heritable neuropsychiatric disorders, although environmental factors, such as maternal immune activation (MIA), play a role as well. Cytokines mediate the effects of MIA on neurogenesis and behavior in animal models. However, MIA stimulators can also induce a febrile reaction, which could have independent effects on neurogenesis through heat shock (HS)-regulated cellular stress pathways. However, this has not been well-studied. To help understand the role of fever in MIA, we used a recently described model of human brain development in which induced pluripotent stem cells (iPSCs) differentiate into 3-dimensional neuronal aggregates that resemble a first trimester telencephalon. RNA-seq was carried out on aggregates that were heat shocked at 39°C for 24 hours, along with their control partners maintained at 37°C. 186 genes showed significant differences in expression following HS (p<0.05), including known HS-inducible genes, as expected, as well as those coding for NGFR and a number of SZ and ASD candidates, including SMARCA2, DPP10, ARNT2, AHI1 and ZNF804A. The degree to which the expression of these genes decrease or increase during HS is similar to that found in copy loss and copy gain copy number variants (CNVs), although the effects of HS are likely to be transient. The dramatic effect on the expression of some SZ and ASD genes places HS, and perhaps other cellular stressors, into a common conceptual framework with disease-causing genetic variants. The findings also suggest that some candidate genes that are assumed to have a relatively limited impact on SZ and ASD pathogenesis based on a small number of positive genetic findings, such as SMARCA2 and ARNT2, may in fact have a much more substantial role in these disorders - as targets of common environmental stressors.

Prenatal immune activation interacts with stress and corticosterone exposure later in life to modulate N-methyl-D-aspartate receptor synaptic function and plasticity

Prenatal infection is an environmental risk factor for schizophrenia while later in life, stressful events have been associated with the onset and severity of psychosis. Recent findings on the impact of stress on the N-methyl-d-aspartate receptor (NMDAR), of which hypofunctioning is implicated in schizophrenia, suggest changes in stress-induced regulation of the glutamatergic system may be related to the pathogenesis of schizophrenia. Our study aimed to test whether prenatal immune activation could interact with stress at adolescence to alter NMDAR function. We used offspring from rat dams administered bacterial lipopolysaccharide (LPS) during pregnancy (gestational days 15 and 16), an animal model expressing schizophrenia-related behavioural phenotypes. Using electrophysiological techniques, we investigated effects of stress and the stress hormone corticosterone (Cort) on NMDAR-mediated synaptic function and long-term depression (LTD) in hippocampal CA1 slices from these adolescent (aged 28-39 d) male offspring. In prenatal LPS offspring, NMDAR-mediated synaptic function and LTD were reduced and abolished, respectively, compared to prenatal saline controls. Notably, in vivo stress and in vitro Cort treatment facilitated LTD in slices from prenatal LPS rats but not prenatal saline controls. Finally, Cort enhanced NMDAR-mediated synaptic function in slices from prenatal LPS rats only. We conclude that prenatal immune activation results in NMDAR hypofunction in the hippocampus of adolescent rats but also increases responsiveness of NMDAR-mediated synaptic function and LTD towards stress. Prenatal infection could confer susceptibility to schizophrenia through modification of hippocampal NMDAR function, with hypofunction in resting conditions and heightened responsiveness to stress, thus impacting the development of the disorder.

Perinatal complications and schizophrenia: involvement of the immune system

The neurodevelopmental hypothesis of schizophrenia suggests that, at least in part, events occurring within the intrauterine or perinatal environment at critical times of brain development underlies emergence of the psychosis observed during adulthood, and brain pathologies that are hypothesized to be from birth. All potential risks stimulate activation of the immune system, and are suggested to act in parallel with an underlying genetic liability, such that an imperfect regulation of the genome mediates these prenatal or early postnatal environmental effects. Epidemiologically based animal models looking at environment and with genes have provided us with a wealth of knowledge in the understanding of the pathophysiology of schizophrenia, and give us the best possibility for interventions and treatments for schizophrenia.

Developmental neuroinflammation and schizophrenia

There is increasing interest in and evidence for altered immune factors in the etiology and pathophysiology of schizophrenia. Stimulated by various epidemiological findings reporting elevated risk of schizophrenia following prenatal exposure to infection, one line of current research aims to explore the potential contribution of immune-mediated disruption of early brain development in the precipitation of long-term psychotic disease. Since the initial formulation of the "prenatal cytokine hypothesis" more than a decade ago, extensive epidemiological research and remarkable advances in modeling prenatal immune activation effects in animal models have provided strong support for this hypothesis by underscoring the critical role of cytokine-associated inflammatory events, together with downstream pathophysiological processes such as oxidative stress, hypoferremia and zinc deficiency, in mediating the short- and long-term neurodevelopmental effects of prenatal infection. Longitudinal studies in animal models further indicate that infection-induced developmental neuroinflammation may be pathologically relevant beyond the antenatal and neonatal periods, and may contribute to disease progression associated with the gradual development of full-blown schizophrenic disease. According to this scenario, exposure to prenatal immune challenge primes early pre- and postnatal alterations in peripheral and central inflammatory response systems, which in turn may disrupt the normal development and maturation of neuronal systems from juvenile to adult stages of life. Such developmental neuroinflammation may adversely affect processes that are pivotal for normal brain maturation, including myelination, synaptic pruning, and neuronal remodeling, all of which occur to a great extent during postnatal brain maturation. Undoubtedly, our understanding of the role of developmental neuroinflammation in progressive brain changes relevant to schizophrenia is still in infancy. Identification of these mechanisms would be highly warranted because they may represent a valuable target to attenuate or even prevent the emergence of full-blown brain and behavioral pathology, especially in individuals with a history of prenatal complications such as in-utero exposure to infection and/or inflammation.

Maternal exposure to lipopolysaccharide leads to transient motor dysfunction in neonatal rats

Epidemiological and experimental data implicate maternal infection and inflammation in the etiology of brain white matter injury, which may lead to cerebral palsy in preterm newborns. Our aim was to investigate motor development of the offspring after maternal administration of lipopolysaccharide (LPS). Wistar rats were intraperitoneally injected with Escherichia coli LPS or saline on gestational days 19 and 20. From birth to 3 weeks, pups were tested for neurobehavioral development, neurological signs and reflexes. From 3 to 6 weeks, motor coordination was investigated. At 4 months, animals were tested for locomotion. Brain myelination was assessed by myelin basic protein immunohistochemistry. Days of appearance of several neurological reflexes were significantly delayed, and neonate LPS pups displayed retarded performance in righting, gait and negative geotaxis. At the juvenile stage, LPS animals showed important impairment in coordination. However, although the LPS group performed worse in most tests, they reached vehicle levels by 5 weeks. At 4 months, LPS animals did not show variations in locomotion performances compared to vehicle. No myelination differences have been observed in the brains at adulthood. Maternal LPS administration results in delayed motor development even though these alterations fade to reach control level by 5 weeks. Motor impairments observed at the early stage in this study could be linked to previously reported hypomyelination of the white matter induced by maternal LPS challenge in the neonates. Finally, the normal myelination shown here at adulthood may explain the functional recovery of the animals and suggest either a potential remyelination of the brain or a delayed myelination in LPS pups.

Prenatal activation of Toll-like receptors-3 by administration of the viral mimetic poly(I:C) changes synaptic proteins, N-methyl-D-aspartate receptors and neurogenesis markers in offspring

Background

There is mounting evidence for a neurodevelopmental basis for disorders such as autism and schizophrenia, in which prenatal or early postnatal events may influence brain development and predispose the young to develop these and related disorders. We have now investigated the effect of a prenatal immune challenge on brain development in the offspring. Pregnant rats were treated with the double-stranded RNA polyinosinic:polycytidylic acid (poly(I:C); 10 mg/kg) which mimics immune activation occurring after activation of Toll-like receptors-3 (TLR3) by viral infection. Injections were made in late gestation (embryonic days E14, E16 and E18), after which parturition proceeded naturally and the young were allowed to develop up to the time of weaning at postnatal day 21 (P21). The brains of these animals were then removed to assess the expression of 13 different neurodevelopmental molecules by immunoblotting.

Results

Measurement of cytokine levels in the maternal blood 5 hours after an injection of poly(I:C) showed significantly increased levels of monocyte chemoattractant protein-1 (MCP-1), confirming immune activation. In the P21 offspring, significant changes were detected in the expression of GluN1 subunits of NMDA receptors, with no difference in GluN2A or GluN2B subunits or the postsynaptic density protein PSD-95 and no change in the levels of the related small GTPases RhoA or RhoB, or the NMDA receptor modulator EphA4. Among presynaptic molecules, a significant increase in Vesicle Associated Membrane Protein-1 (VAMP-1; synaptobrevin) was seen, with no change in synaptophysin or synaptotagmin. Proliferating Cell Nuclear Antigen (PCNA), as well as the neurogenesis marker doublecortin were unchanged, although Sox-2 levels were increased, suggesting possible changes in the rate of new cell differentiation.

Conclusions

The results reveal the induction by prenatal poly(I:C) of selective molecular changes in the brains of P21 offspring, affecting primarily molecules associated with neuronal development and synaptic transmission. These changes may contribute to the behavioural abnormalities that have been reported in adult animals after exposure to poly(I:C) and which resemble symptoms seen in schizophrenia and related disorders.

A lifespan approach to neuroinflammatory and cognitive disorders: a critical role for glia

Cognitive decline is a common problem of aging. Whereas multiple neural and glial mechanisms may account for these declines, microglial sensitization and/or dystrophy has emerged as a leading culprit in brain aging and dysfunction. However, glial activation is consistently observed in normal brain aging as well, independent of frank neuroinflammation or functional impairment. Such variability suggests the existence of additional vulnerability factors that can impact neuronal-glial interactions and thus overall brain and cognitive health. The goal of this review is to elucidate our working hypothesis that an individual's risk or resilience to neuroinflammatory disorders and poor cognitive aging may critically depend on their early life experience, which can change immune reactivity within the brain for the remainder of the lifespan. For instance, early-life infection in rats can profoundly disrupt memory function in young adulthood, as well as accelerate age-related cognitive decline, both of which are linked to enduring changes in glial function that occur in response to the initial infection. We discuss these findings within the context of the growing literature on the role of immune molecules and neuroimmune crosstalk in normal brain development. We highlight the intrinsic factors (e.g., chemokines, hormones) that regulate microglial development and their colonization of the embryonic and postnatal brain, and the capacity for disruption or "re-programming" of this crucial process by external events (e.g., stress, infection). An impact on glia, which in turn alters neural development, has the capacity to profoundly impact cognitive and mental health function at all stages of life.

Association of GRIN1 and GRIN2A-D with schizophrenia and genetic interaction with maternal herpes simplex virus-2 infection affecting disease risk

N-methyl-D-aspartate (NMDA) receptors are very important for proper brain development and several lines of evidence support that hypofunction of the NMDA receptors are involved in the pathophysiology of schizophrenia. Gene variation and gene-environmental interactions involving the genes encoding the NMDA receptors are therefore likely to influence the risk of schizophrenia. The aim of this study was to determine (1) whether SNP variation in the genes (GRIN1, GRIN2A, GRIN2B, GRIN2C, and GRIN2D) encoding the NMDA receptor were associated with schizophrenia; (2) whether GRIN gene variation in the offspring interacted with maternal herpes simplex virus-2 (HSV-2) seropositivity during pregnancy influencing the risk of schizophrenia later in life. Individuals from three independently collected Danish case control samples were genotyped for 81 tagSNPs (in total 984 individuals diagnosed with schizophrenia and 1,500 control persons) and antibodies against maternal HSV-2 infection were measured in one of the samples (365 cases and 365 controls). Nine SNPs out of 30 in GRIN2B were significantly associated with schizophrenia. One SNP remained significant after Bonferroni correction (rs1806194, P(nominal)  = 0.0008). Significant interaction between maternal HSV-2 seropositivity and GRIN2B genetic variation in the offspring were observed for seven SNPs and two remained significant after Bonferroni correction (rs1805539, P(nominal)  = 0.0001 and rs1806205, P(nominal)  = 0.0008). The significant associations and interactions were located at the 3' region of GRIN2B suggesting that genetic variation in this part of the gene may be involved in the pathophysiology of schizophrenia.

Early, time-dependent disturbances of hippocampal synaptic transmission and plasticity after in utero immune challenge

BACKGROUND

Maternal infection during pregnancy is a recognized risk factor for the occurrence of a broad spectrum of psychiatric and neurologic disorders, including schizophrenia, autism, and cerebral palsy. Prenatal exposure of rats to lipopolysaccharide (LPS) leads to impaired learning and psychotic-like behavior in mature offspring, together with an enduring modification of glutamatergic excitatory synaptic transmission. The question that arises is whether any alterations of excitatory transmission and plasticity occurred at early developmental stages after in utero LPS exposure.

METHODS

Electrophysiological experiments were carried out on the CA1 area of hippocampal slices from prenatally LPS-exposed male offspring from 4 to 190 days old to study the developmental profiles of long-term depression (LTD) triggered by delivering 900 shocks either single- or paired-pulse (50-msec interval) at 1 Hz and the N-methyl-D-aspartate receptor (NMDAr) contribution to synaptic transmission.

RESULTS

The age-dependent drop of LTD is accelerated in prenatally LPS-exposed animals, and LTD is transiently converted into a slow-onset long-term potentiation between 16 and 25 days old. This long-term potentiation depends on Group I metabotropic glutamate receptors and protein kinase A activations and is independent of NMDArs. Maternal LPS challenge also leads to a rapid developmental impairment of synaptic NMDArs. This was associated with a concomitant reduced expression of GluN1, without any detectable alteration in the developmental switch of NMDAr GluN2 subunits.

CONCLUSIONS

Aberrant forms of synaptic plasticity can be detected at early developmental stages after prenatal LPS challenge concomitant with a clear hypo-functioning of the NMDAr in the hippocampus. This might result in later-occurring brain dysfunctions.

Alterations in cognitive function and behavioral response to amphetamine induced by prenatal inflammation are dependent on the stage of pregnancy

Maternal infection during human pregnancy has been associated with the development of schizophrenia in the adult offspring. The stage of development and the maternal inflammatory response to infection, which undergoes quantitative and qualitative changes throughout gestation, are thought to determine critical windows of vulnerability for the developing brain. In order to investigate how these two factors may contribute to the outcome in the offspring, we studied the inflammatory response to turpentine (TURP) injection (100 μl/dam) and its consequences in the adult offspring, in pregnant rats at gestational day (GD) 15 or 18, which correspond to late first and early second trimester of human pregnancy, respectively. Maternal inflammatory response to TURP was different between the two GDs, with fever and circulating levels of the pro-inflammatory interleukin (IL)-6 significantly attenuated at GD 18, compared to GD 15. In the adult offspring, TURP challenge at GD 15 induced a significant decrease in pre-pulse inhibition (PPI) of acoustic startle, increased latency in the cued task of the Morris-water maze, prolonged conditioned fear response and enhanced locomotor effect of amphetamine. In contrast, the same immune challenge at GD 18 induced only a prolonged conditioned fear response. These results suggest a window of vulnerability at GD 15, at which TURP seems to affect several behaviors that are strongly modulated by dopamine. This was supported by increased tyrosine hydroxylase expression in the nucleus accumbens of the adult offspring of mothers treated at GD 15.

Modeling autistic features in animals

A variety of features of autism can be simulated in rodents, including the core behavioral hallmarks of stereotyped and repetitive behaviors, and deficits in social interaction and communication. Other behaviors frequently found in autism spectrum disorders (ASDs) such as neophobia, enhanced anxiety, abnormal pain sensitivity and eye blink conditioning, disturbed sleep patterns, seizures, and deficits in sensorimotor gating are also present in some of the animal models. Neuropathology and some characteristic neurochemical changes that are frequently seen in autism, and alterations in the immune status in the brain and periphery are also found in some of the models. Several known environmental risk factors for autism have been successfully established in rodents, including maternal infection and maternal valproate administration. Also under investigation are a number of mouse models based on genetic variants associated with autism or on syndromic disorders with autistic features. This review briefly summarizes recent developments in this field, highlighting models with face and/or construct validity, and noting the potential for investigation of pathogenesis, and early progress toward clinical testing of potential therapeutics. Wherever possible, reference is made to reviews rather than to primary articles.

Early life infection alters adult BALB/c hippocampal gene expression in a sex specific manner

During the perinatal period, the developing brain is sensitive to environmental events. Deleterious programing resulting from infection, dietary restriction, or psychological stress has been observed and affects adult immune and endocrine systems as well as behavior. In this study, we determined whether neonatal infection permanently alters immune and glucocorticoid receptor signaling pathways in the adult hippocampus. A Chlamydia muridarum respiratory infection was induced in male and female mice at birth. Mice were allowed to recover and microarray analysis was conducted on RNA from adult hippocampal tissue. In males, neonatal infection induced an up-regulation of genes associated with cellular development, nervous system development and function, such as cyclin-dependent kinase inhibitor 1A. After neonatal infection, adult females exhibited a T-helper 2 immune bias with genes such as major histocompatibility complex, class II, DQ beta 1 up-regulated. Expression of prolactin, vasopressin, hypocretin, corticotrophin-releasing hormone-binding protein, and oxytocin were confirmed by quantitative real-time polymerase chain reaction. This study shows that neonatal infection differentially alters the gene expression profiles of both female and male mice along immune and neuroendocrine pathways.

Prenatal stress: role in psychotic and depressive diseases

RATIONALE

The birth of neurons, their migration to appropriate positions in the brain, and their establishment of the proper synaptic contacts happen predominately during the prenatal period. Environmental stressors during gestation can exert a major impact on brain development and thereby contribute to the pathogenesis of neuropsychiatric illnesses, such as depression and psychotic disorders including schizophrenia.

OBJECTIVE

The objectives here are to present recent preclinical studies of the impact of prenatal exposure to gestational stressors on the developing fetal brain and discuss their relevance to the neurobiological basis of mental illness. The focus is on maternal immune activation, psychological stresses, and malnutrition, due to the abundant clinical literature supporting their role in the etiology of neuropsychiatric illnesses.

RESULTS

Prenatal maternal immune activation, viral infection, unpredictable psychological stress, and malnutrition all appear to foster the development of behavioral abnormalities in exposed offspring that may be relevant to the symptom domains of schizophrenia and psychosis, including sensorimotor gating, information processing, cognition, social function, and subcortical hyperdopaminergia. Depression-related phenotypes, such as learned helplessness or anxiety, are also observed in some model systems. These changes appear to be mediated by the presence of proinflammatory cytokines and/or corticosteroids in the fetal compartment that alter the development the neuroanatomical substrates involved in these behaviors.

CONCLUSION

Prenatal exposure to environmental stressors alters the trajectory of brain development and can be used to generate animal preparations that may be informative in understanding the pathophysiological processes involved in several human neuropsychiatric disorders.

Prenatal interaction of mutant DISC1 and immune activation produces adult psychopathology

BACKGROUND

Gene-environment interactions (GEI) are involved in the pathogenesis of mental diseases. We evaluated interaction between mutant human disrupted-in-schizophrenia 1 (mhDISC1) and maternal immune activation implicated in schizophrenia and mood disorders.

METHODS

Pregnant mice were treated with saline or polyinosinic:polycytidylic acid at gestation day 9. Levels of inflammatory cytokines were measured in fetal and adult brains; expression of mhDISC1, endogenous DISC1, lissencephaly type 1, nuclear distribution protein nudE-like 1, glycoprotein 130, growth factor receptor-bound protein 2, and glycogen synthase kinase-3beta were assessed in cortical samples of newborn mice. Tissue content of monoamines, volumetric brain abnormalities, dendritic spine density in the hippocampus, and various domains of the mouse behavior repertoire were evaluated in adult male mice.

RESULTS

Prenatal interaction produced anxiety, depression-like responses, and altered social behavior that were accompanied by decreased reactivity of the hypothalamic-pituitary-adrenal axis, attenuated serotonin neurotransmission in the hippocampus, reduced enlargement of lateral ventricles, decreased volumes of amygdala and periaqueductal gray matter and density of spines on dendrites of granule cells of the hippocampus. Prenatal interaction modulated secretion of inflammatory cytokines in fetal brains, levels of mhDISC1, endogenous mouse DISC1, and glycogen synthase kinase-3beta. The behavioral effects of GEI were observed only if mhDISC1 was expressed throughout the life span.

CONCLUSIONS

Prenatal immune activation interacted with mhDISC1 to produce the neurobehavioral phenotypes that were not seen in untreated mhDISC1 mice and that resemble aspects of major mental illnesses. Our DISC1 mouse model is a valuable system to study GEI relevant to mental illnesses.

High-dose oxytocin is not associated with maternal temperature elevation: a retrospective cohort study of mid-trimester pregnancy with intrauterine fetal demise

BACKGROUND

Maternal intrapartum fever has been associated with an increased incidence of neonatal morbidity. In this retrospective cohort study, we evaluated whether intravenous oxytocin has a fever-inducing effect. Oxytocin augments secretion of prostaglandins E(2) and F(2α) which are inflammatory mediators known to elevate body temperature.

METHODS

Between January 2005 and June 2008, 279 patients were admitted with mid-trimester fetal demise. Patients meeting inclusion criteria included 34 women who received a high-dose intravenous oxytocin regimen and 29 patients who delivered after spontaneous labor without the need for augmentation. Oral temperatures were measured on admission and at delivery.

RESULTS

The median length of oxytocin infusion was 5.3h. The calculated temperature change was -0.14°C in the oxytocin group and +0.12°C in the control group. These findings were confirmed in a model adjusted for patients' white blood cell count and duration of labor. We did not observe an effect of analgesia type, epidural versus intravenous analgesia, on duration of labor.

CONCLUSION

Based on this comparative analysis of pregnant women who received high-doses of oxytocin, we found insufficient evidence to support that high-dose intravenous oxytocin elevates intrapartum maternal temperature.

Challenges to maternal wellbeing during pregnancy impact temperament, attention, and neuromotor responses in the infant rhesus monkey

The relative maturity, alertness, and reactivity of an infant at birth are sensitive indices of the neonate's health, the quality of the pregnancy, and the mother's wellbeing. Even when fetal growth and gestation length have been normal, the maturing fetus can still be adversely impacted by both physical events and psychological challenges to the mother during the prenatal period. The following research evaluated 413 rhesus monkeys from 7 different types of pregnancies to determine which conditions significantly influenced the behavioral responsiveness and state of the young infant. A standardized test battery modeled after the Neonatal Behavioral Assessment Scale for human newborns was employed. The largest impairments in orientation and increases in infant emotional reactivity were seen when female monkeys drank alcohol, even though consumed at only moderate levels during part of the pregnancy. The infants' ability to focus and attend to visual and auditory cues was also affected when the gravid female's adrenal hormones were transiently elevated for 2 weeks by ACTH administration. In addition, responses to tactile and vestibular stimulation were altered by both this ACTH treatment and psychological disturbance during gestation. Conversely, a 2-day course of antenatal corticosteroids 1 month before term resulted in infants with lower motor activity and reactivity. These findings highlight several pregnancy conditions that can affect a young infant's neurobehavioral status, even when otherwise healthy, and demonstrate that alterations or deficits are specific to the type of insult experienced by the mother and fetus.

Prenatal inflammation-induced hypoferremia alters dopamine function in the adult offspring in rat: relevance for schizophrenia

Maternal infection during pregnancy has been associated with increased incidence of schizophrenia in the adult offspring. Mechanistically, this has been partially attributed to neurodevelopmental disruption of the dopamine neurons, as a consequence of exacerbated maternal immunity. In the present study we sought to target hypoferremia, a cytokine-induced reduction of serum non-heme iron, which is common to all types of infections. Adequate iron supply to the fetus is fundamental for the development of the mesencephalic dopamine neurons and disruption of this following maternal infection can affect the offspring's dopamine function. Using a rat model of localized injury induced by turpentine, which triggers the innate immune response and inflammation, we investigated the effects of maternal iron supplementation on the offspring's dopamine function by assessing behavioral responses to acute and repeated administration of the dopamine indirect agonist, amphetamine. In addition we measured protein levels of tyrosine hydroxylase, and tissue levels of dopamine and its metabolites, in ventral tegmental area, susbtantia nigra, nucleus accumbens, dorsal striatum and medial prefrontal cortex. Offspring of turpentine-treated mothers exhibited greater responses to a single amphetamine injection and enhanced behavioral sensitization following repeated exposure to this drug, when compared to control offspring. These behavioral changes were accompanied by increased baseline levels of tyrosine hydroxylase, dopamine and its metabolites, selectively in the nucleus accumbens. Both, the behavioral and neurochemical changes were prevented by maternal iron supplementation. Localized prenatal inflammation induced a deregulation in iron homeostasis, which resulted in fundamental alterations in dopamine function and behavioral alterations in the adult offspring. These changes are characteristic of schizophrenia symptoms in humans.

TLR2 activation inhibits embryonic neural progenitor cell proliferation

Toll-like receptors (TLRs) play essential roles in innate immunity, and increasing evidence indicates that these receptors are expressed in neurons, astrocytes, and microglia in the brain, where they mediate responses to infection, stress, and injury. To address the possibility that TLR2 heterodimer activation could affect progenitor cells in the developing brain, we analyzed the expression of TLR2 throughout mouse cortical development, and assessed the role of TLR2 heterodimer activation in neuronal progenitor cell (NPC) proliferation. TLR2 mRNA and protein was expressed in the cortex in embryonic and early postnatal stages of development, and in cultured cortical NPC. While NPC from TLR2-deficient and wild type embryos had the same proliferative capacity, TLR2 activation by the synthetic bacterial lipopeptides Pam(3)CSK(4) and FSL1, or low molecular weight hyaluronan, an endogenous ligand for TLR2, inhibited neurosphere formation in vitro. Intracerebral in utero administration of TLR2 ligands resulted in ventricular dysgenesis characterized by increased ventricle size, reduced proliferative area around the ventricles, increased cell density, an increase in phospho-histone 3 cells, and a decrease in BrdU(+) cells in the sub-ventricular zone. Our findings indicate that loss of TLR2 does not result in defects in cerebral development. However, TLR2 is expressed and functional in the developing telencephalon from early embryonic stages and infectious agent-related activation of TLR2 inhibits NPC proliferation. TLR2-mediated inhibition of NPC proliferation may therefore be a mechanism by which infection, ischemia, and inflammation adversely affect brain development.