Maternal immune activation alters fetal brain development through interleukin-6

Prenatal infection and schizophrenia: a review of epidemiologic and translational studies

An emerging literature from epidemiologic, clinical, and preclinical investigations has provided evidence that gestational exposure to infection contributes to the etiology of schizophrenia. In recent years, these studies have moved from ecologic designs, which ascertain infection based on epidemics in populations, to investigations that have capitalized on reliable biomarkers in individual pregnancies. These studies have documented specific candidate infections that appear to be associated with an elevated risk of schizophrenia. Animal models of maternal immune activation inspired by this work have revealed intriguing findings indicating behavioral, neurochemical, and neurophysiologic abnormalities consistent with observations in schizophrenia. In parallel studies in humans and animals, investigators are working to uncover the cellular and molecular mechanisms by which in utero exposure to infection contributes to schizophrenia risk. In this review, the authors discuss and critically evaluate the epidemiologic literature on in utero exposure to infection and schizophrenia, summarize emerging animal models of maternal immune activation, and discuss putative unique and common mechanisms by which in utero exposure to infection alters neurodevelopment, potentially increasing susceptibility to schizophrenia. The promise of this work for facilitating the identification of susceptibility loci in genetic studies of schizophrenia is illustrated by examples of interaction between in utero exposure to infection and genetic variants. The authors then elaborate on possible implications of this work, including the use of preventive measures for reducing the incidence of schizophrenia. Finally, they discuss new approaches aimed at addressing current challenges in this area of research.

Vitamin D status during pregnancy and aspects of offspring health

Low maternal vitamin D levels during pregnancy have been linked to various health outcomes in the offspring, ranging from periconceptional effects to diseases of adult onset. Maternal and infant cord 25(OH)D levels are highly correlated. Here, we review the available evidence for these adverse health effects. Most of the evidence has arisen from observational epidemiological studies, but randomized controlled trials are now underway. The evidence to date supports that women should be monitored and treated for vitamin D deficiency during pregnancy but optimal and upper limit serum 25(OH)D levels during pregnancy are not known.

Nonpharmacological Interventions for the Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, autoimmune disease that affects approximately 1.3 million Americans. It is characterized by inflammation of the joints, most often affecting the hands, hips, and knees. Presently, there is no cure, and the commonly used pharmacological therapies are not always effective and have significant side effects, especially when used long term. Consequently, there is a need for alternative treatments for RA. Mind-body medicine (MBM), which uses the mind to affect disease processes, is a promising area for many pathological conditions, especially autoimmune disorders like RA. In this review, we highlight the basis for psychological-based interventions for the treatment of RA. The notion that the mind has an impact on immune function and several processes that underpin the pathophysiology of RA is well established. Correspondingly, there are several lines of evidence to indicate that psychological-based interventions can favorably affect these processes. Clinical trials of MBM in RA have most commonly assessed outcomes such as pain, functional disability, psychological status, coping abilities, self-efficacy, and joint involvement. Across studies, statistically significant improvements were found for all outcomes, though the clinical significance of these changes is open to interpretation. Given that the RA patients included in these studies had generally maximized the use of pharmacological options, any additional therapeutic benefit may be considered significant. Patients with a history of depression appear to exhibit heightened responsiveness to MBM, and this is a group that should be preferentially targeted. Based on the current evidence, MBM can be recommended as an adjunct to conventional therapy to enhance treatment response and possibly reduce the use of more risky pharmacological therapies.

Lingering prenatal effects of the 1918 influenza pandemic on cardiovascular disease

Prenatal exposure to the 1918 influenza pandemic (Influenza A, H1N1 subtype) is associated with ⩾20% excess cardiovascular disease at 60 to 82 years of age, relative to cohorts born without exposure to the influenza epidemic, either prenatally or postnatally (defined by the quarter of birth), in the 1982-1996 National Health Interview Surveys of the USA. Males showed stronger effects of influenza on increased later heart disease than females. Adult height at World War II enlistment was lower for the 1919 birth cohort than for those born in adjacent years, suggesting growth retardation. Calculations on the prevalence of maternal infections indicate that prenatal exposure to even uncomplicated maternal influenza may have lasting consequences later in life. These findings suggest novel roles for maternal infections in the fetal programming of cardiovascular risk factors that are independent of maternal malnutrition.

Constitutive genetic deletion of the growth regulator Nogo-A induces schizophrenia-related endophenotypes

The membrane protein Nogo-A, which is predominantly expressed by oligodendrocytes in the adult CNS and by neurons mainly during development, is well known for limiting neurite outgrowth and regeneration in the injured mammalian CNS. In addition, it has recently been proposed that abnormal Nogo-A expression or Nogo receptor (NgR) mutations may confer genetic risks for neuropsychiatric disorders of presumed neurodevelopmental origin, such as schizophrenia. We therefore evaluated whether Nogo-A deletion may lead to schizophrenia-like abnormalities in a mouse model of genetic Nogo-A deficiency. Here, we show that systemic, lifelong knock-out of the Nogo-A gene can lead to specific behavioral abnormalities resembling schizophrenia-related endophenotypes: deficient sensorimotor gating, disrupted latent inhibition, perseverative behavior, and increased sensitivity to the locomotor stimulating effects of amphetamine. These behavioral phenotypes were accompanied by altered monoaminergic transmitter levels in specific striatal and limbic structures, as well as changes in dopamine D2 receptor expression in the same brain regions. Nogo-A deletion was further associated with elevated expression of growth-related markers. In contrast, acute antibody-mediated Nogo-A neutralization in adult wild-type mice failed to produce such phenotypes, suggesting that the phenotypes observed in the knock-out mice might be of developmental origin, and that Nogo-A normally subserves critical functions in neurodevelopment. This study provides the first experimental demonstration that Nogo-A bears neuropsychiatric relevance, and alterations in its expression may be one etiological factor in schizophrenia and related disorders.

Combined effect of neonatal immune activation and mutant DISC1 on phenotypic changes in adulthood

Gene-environment interaction may play a role in the etiology of schizophrenia. Transgenic mice expressing dominant-negative DISC1 (DN-DISC1 mice) show some histological and behavioral endophenotypes relevant to schizophrenia. Viral infection during neurodevelopment provides a major environmental risk for schizophrenia. Neonatal injection of polyriboinosinic-polyribocytidylic acid (polyI:C), which mimics innate immune responses elicited by viral infection, leads to schizophrenia-like behavioral alteration in mice after puberty. To study how gene-environmental interaction during neurodevelopment results in phenotypic changes in adulthood, we treated DN-DISC1 mice or wild-type littermates with injection of polyI:C during the neonatal stage, according to the published method, respectively, and the behavioral and histological phenotypes were examined in adulthood. We demonstrated that neonatal polyI:C treatment in DN-DISC1 mice resulted in the deficits of short-term, object recognition, and hippocampus-dependent fear memories after puberty, although polyI:C treatment by itself had smaller influences on wild-type mice. Furthermore, polyI:C-treated DN-DISC1 mice exhibited signs of impairment of social recognition and interaction, and augmented susceptibility to MK-801-induced hyperactivity as compared with vehicle-treated wild-type mice. Of most importance, additive effects of polyI:C and DN-DISC1 were observed by a marked decrease in parvalbumin-positive interneurons in the medial prefrontal cortex. These results suggest that combined effect of neonatal polyI:C treatment and DN-DISC1 affects some behavioral and histological phenotypes in adulthood.

Depressive symptoms predict exaggerated inflammatory responses to an in vivo immune challenge among pregnant women

OBJECTIVE

Stress and depressive symptoms predict exaggerated inflammatory responses to a biological challenge in nonpregnant humans and animals. The extent to which these findings generalize to pregnancy is unknown because the immune system exhibits substantial changes to support pregnancy. Notably, inflammatory responses to infectious agents play a causal role in the development of gestational hypertension as well as risk for preterm birth. Thus, depressive symptoms may increase susceptibility to these outcomes via sensitization of inflammatory processes. The current study was designed to test the hypothesis that depressive symptoms would predict an exaggerated proinflammatory response to an in vivo antigen challenge, influenza virus vaccination, among pregnant women.

METHOD

Twenty-two pregnant women completed two study visits: baseline and 1week after receiving influenza virus vaccination. Depressive symptoms were measured with the Center for Epidemiologic Studies Depression Scale (CES-D) at baseline. Serum levels of macrophage migration inhibitory factor (MIF) were determined using a high sensitivity immunoassay at both study visits.

OUTCOMES

Analyses demonstrated that, as compared to those in the lowest tertile of CES-D scores, those in the highest tertile exhibited significantly higher levels of MIF 1week after influenza virus vaccination (p=.035).

CONCLUSIONS

Depressive symptoms predicted exaggerated MIF production following influenza virus vaccination during pregnancy. These data support the hypothesis that depressive symptoms are associated with sensitization of the inflammatory response during pregnancy. Thus, women with greater depressive symptoms may be more vulnerable to negative sequelae of infectious illness during pregnancy.

Models of neurodevelopmental abnormalities in schizophrenia

The neurodevelopmental hypothesis of schizophrenia asserts that the underlying pathology of schizophrenia has its roots in brain development and that these brain abnormalities do not manifest themselves until adolescence or early adulthood. Animal models based on developmental manipulations have provided insight into the vulnerability of the developing fetus and the importance of the early environment for normal maturation. These models have provided a wide range of validated approaches to answer questions regarding environmental influences on both neural and behavioral development. In an effort to better understand the developmental hypothesis of schizophrenia, animal models have been developed, which seek to model the etiology and/or the pathophysiology of schizophrenia or specific behaviors associated with the disease. Developmental models specific to schizophrenia have focused on epidemiological risk factors (e.g., prenatal viral insult, birth complications) or more heuristic models aimed at understanding the developmental neuropathology of the disease (e.g., ventral hippocampal lesions). The combined approach of behavioral and neuroanatomical evaluation of these models strengthens their utility in improving our understanding of the pathophysiology of schizophrenia and developing new treatment strategies.

Differential monocyte responses to TLR ligands in children with autism spectrum disorders

Autism spectrum disorders (ASD) are characterized by impairment in social interactions, communication deficits, and restricted repetitive interests and behaviors. Recent evidence has suggested that impairments of innate immunity may play an important role in ASD. To test this hypothesis, we isolated peripheral blood monocytes from 17 children with ASD and 16 age-matched typically developing (TD) controls and stimulated these cell cultures in vitro with distinct toll-like receptors (TLR) ligands: TLR 2 (lipoteichoic acid; LTA), TLR 3 (poly I:C), TLR 4 (lipopolysaccharide; LPS), TLR 5 (flagellin), and TLR 9 (CpG-B). Supernatants were harvested from the cell cultures and pro-inflammatory cytokine responses for IL-1beta, IL-6, IL-8, TNFalpha, MCP-1, and GM-CSF were determined by multiplex Luminex analysis. After in vitro challenge with TLR ligands, differential cytokine responses were observed in monocyte cultures from children with ASD compared with TD control children. In particular, there was a marked increase in pro-inflammatory IL-1beta, IL-6, and TNFalpha responses following TLR 2, and IL-1beta response following TLR 4 stimulation in monocyte cultures from children with ASD (p<0.04). Conversely, following TLR 9 stimulation there was a decrease in IL-1beta, IL-6, GM-CSF, and TNFalpha responses in monocyte cell cultures from children with ASD compared with controls (p<0.05). These data indicate that, monocyte cultures from children with ASD are more responsive to signaling via select TLRs. As monocytes are key regulators of the immune response, dysfunction in the response of these cells could result in long-term immune alterations in children with ASD that may lead to the development of adverse neuroimmune interactions and could play a role in the pathophysiology observed in ASD.

Prepulse inhibition and genetic mouse models of schizophrenia

Mutant mouse models related to schizophrenia have been based primarily on the pathophysiology of schizophrenia, the known effects of antipsychotic drugs, and candidate genes for schizophrenia. Sensorimotor gating deficits in schizophrenia patients, as indexed by measures of prepulse inhibition of startle (PPI), have been well characterized and suggested to meet the criteria as a useful endophenotype in human genetic studies. PPI refers to the ability of a non-startling "prepulse" to inhibit responding to the subsequent startling stimulus or "pulse." Because of the cross-species nature of PPI, it has been used primarily in pharmacological animal models to screen putative antipsychotic medications. As techniques in molecular genetics have progressed over the past 15 years, PPI has emerged as a phenotype used in assessing genetic mouse models of relevance to schizophrenia. In this review, we provide a selected overview of the use of PPI in mouse models of schizophrenia and discuss the contribution and usefulness of PPI as a phenotype in the context of genetic mouse models. To that end, we discuss mutant mice generated to address hypotheses regarding the pathophysiology of schizophrenia and candidate genes (i.e., hypothesis driven). We also briefly discuss the usefulness of PPI in phenotype-driven approaches in which a PPI phenotype could lead to "bottom up" approaches of identifying novel genes of relevance to PPI (i.e., hypothesis generating).

Cerebral cortical thickness and a history of obstetric complications in schizophrenia

INTRODUCTION

Magnetic resonance imaging (MRI) studies have demonstrated that patients with schizophrenia have thinner brain cortices compared with healthy control subjects. Neurodevelopment is vulnerable to obstetric complications (OCs) such as hypoxia and birth trauma, factors that are also related to increased risk of developing schizophrenia. With the hypothesis that OCs might explain the thinner cortices found in schizophrenia, we studied patients with schizophrenia and healthy controls subjects for association between number and severity of OCs and variation in cortical thickness.

METHODS

MRI scans of 54 adults with schizophrenia or schizoaffective disorder and 54 healthy controls were acquired at Karolinska Institutet, Stockholm, Sweden. Measures of brain cortical thickness were obtained using automated computer processing (FreeSurfer). OCs were assessed from obstetric records and scored blindly according to the McNeil-Sjöström scale. At numerous cortical locations, putative effects of OCs on cortical thickness variation were tested for each trimester, for labour, for composite OC scores, severe OC scores, and hypoxia scores among patients and controls separately.

RESULTS

Number and severity of OCs varied among both patient and control subjects but were not associated with cortical thickness in either of the groups. Patients demonstrated thinner brain cortices but there were no significant differences in number and severity of OC scores across groups.

CONCLUSION

In the present study, number and severity of obstetric complications were not associated with brain cortical thickness, in patients with schizophrenia or in healthy control subjects. The thinner brain cortices found in patients with schizophrenia were not explained by a history of OCs.

Cytokines and CNS development

Cytokines are pleotrophic proteins that coordinate the host response to infection as well as mediate normal, ongoing signaling between cells of nonimmune tissues, including the nervous system. As a consequence of this dual role, cytokines induced in response to maternal infection or prenatal hypoxia can profoundly impact fetal neurodevelopment. The neurodevelopmental roles of individual cytokine signaling pathways are being elucidated through gain- and loss-of-function studies in cell culture and model organisms. We review this work with a particular emphasis on studies where cytokines, their receptors, or components of their signaling pathways have been altered in vivo. The extensive and diverse requirements for properly regulated cytokine signaling during normal nervous system development revealed by these studies sets the foundation for ongoing and future work aimed at understanding how cytokines induced normally and pathologically during critical stages of fetal development alter nervous system function and behavior later in life.

Prenatal exposure to infection: a primary mechanism for abnormal dopaminergic development in schizophrenia

RATIONALE

Prenatal exposure to infection is a notable environmental risk factor in the development of schizophrenia. One prevalent hypothesis suggests that infection-induced disruption of early prenatal brain development predisposes the organism to long-lasting structural and functional brain abnormalities. Many of the prenatal infection-induced functional brain abnormalities appear to be closely associated with imbalances in the mesocorticolimbic dopamine system in adult life, suggesting that disruption of functional and structural dopaminergic development may be at the core of the developmental neuropathology associated with psychosis-related abnormalities induced by prenatal exposure to infection.

OBJECTIVES

In this review, we integrate recent findings derived from experimental models in animals with parallel research in humans which supports this hypothesis. We thereby highlight the developmental perspective of abnormal DA functions following in-utero exposure to infection in relation to the developmental and maturational mechanisms potentially involved in schizophrenia.

RESULTS

Experimental investigations show that early prenatal immune challenge can lead to the emergence of early structural and functional alterations in the mesocorticolimbic DA system, long before the onset of the full spectrum of psychosis-associated behavioral and cognitive abnormalities in adulthood.

CONCLUSIONS

Dopaminergic mal-development in general, and following prenatal immune activation in particular, may represent a primary etiopathological mechanism in the development of schizophrenia and related disorders. This hypothesis differs from the view that dopaminergic abnormalities in schizophrenia may be secondary to abnormalities in other brain structures and/or neurotransmitter systems. The existence of primary dopaminergic mechanisms may have important implications for the identification and early treatment of individuals prodromally symptomatic for schizophrenia.

Schizophrenia susceptibility genes directly implicated in the life cycles of pathogens: cytomegalovirus, influenza, herpes simplex, rubella, and Toxoplasma gondii

Many genes implicated in schizophrenia can be related to glutamatergic transmission and neuroplasticity, oligodendrocyte function, and other families clearly related to neurobiology and schizophrenia phenotypes. Others appear rather to be involved in the life cycles of the pathogens implicated in the disease. For example, aspartylglucosaminidase (AGA), PLA2, SIAT8B, GALNT7, or B3GAT1 metabolize chemical ligands to which the influenza virus, herpes simplex, cytomegalovirus (CMV), rubella, or Toxoplasma gondii bind. The epidermal growth factor receptor (EGR/EGFR) is used by the CMV to gain entry to cells, and a CMV gene codes for an interleukin (IL-10) mimic that binds the host cognate receptor, IL10R. The fibroblast growth factor receptor (FGFR1) is used by herpes simplex. KPNA3 and RANBP5 control the nuclear import of the influenza virus. Disrupted in schizophrenia 1 (DISC1) controls the microtubule network that is used by viruses as a route to the nucleus, while DTNBP1, MUTED, and BLOC1S3 regulate endosomal to lysosomal routing that is also important in viral traffic. Neuregulin 1 activates ERBB receptors releasing a factor, EBP1, known to inhibit the influenza virus transcriptase. Other viral or bacterial components bind to genes or proteins encoded by CALR, FEZ1, FYN, HSPA1B, IL2, HTR2A, KPNA3, MED12, MED15, MICB, NQO2, PAX6, PIK3C3, RANBP5, or TP53, while the cerebral infectivity of the herpes simplex virus is modified by Apolipoprotein E (APOE). Genes encoding for proteins related to the innate immune response, including cytokine related (CCR5, CSF2RA, CSF2RB, IL1B, IL1RN, IL2, IL3, IL3RA, IL4, IL10, IL10RA, IL18RAP, lymphotoxin-alpha, tumor necrosis factor alpha [TNF]), human leukocyte antigen (HLA) antigens (HLA-A10, HLA-B, HLA-DRB1), and genes involved in antigen processing (angiotensin-converting enzyme and tripeptidyl peptidase 2) are all concerned with defense against invading pathogens. Human microRNAs (Hsa-mir-198 and Hsa-mir-206) are predicted to bind to influenza, rubella, or poliovirus genes. Certain genes associated with schizophrenia, including those also concerned with neurophysiology, are intimately related to the life cycles of the pathogens implicated in the disease. Several genes may affect pathogen virulence, while the pathogens in turn may affect genes and processes relevant to the neurophysiology of schizophrenia. For such genes, the strength of association in genetic studies is likely to be conditioned by the presence of the pathogen, which varies in different populations at different times, a factor that may explain the heterogeneity that plagues such studies. This scenario also suggests that drugs or vaccines designed to eliminate the pathogens that so clearly interact with schizophrenia susceptibility genes could have a dramatic effect on the incidence of the disease.

Immune influence on adult neural stem cell regulation and function

Neural stem cells (NSCs) lie at the heart of central nervous system development and repair, and deficiency or dysregulation of NSCs or their progeny can have significant consequences at any stage of life. Immune signaling is emerging as one of the influential variables that define resident NSC behavior. Perturbations in local immune signaling accompany virtually every injury or disease state, and signaling cascades that mediate immune activation, resolution, or chronic persistence influence resident stem and progenitor cells. Some aspects of immune signaling are beneficial, promoting intrinsic plasticity and cell replacement, while others appear to inhibit the very type of regenerative response that might restore or replace neural networks lost in injury or disease. Here we review known and speculative roles that immune signaling plays in the postnatal and adult brain, focusing on how environments encountered in disease or injury may influence the activity and fate of endogenous or transplanted NSCs.

Autism: an emerging 'neuroimmune disorder' in search of therapy

BACKGROUND

Autism spectrum disorders (ASDs) are neurodevelopmental disorders characterized by difficulties in communication and by repetitive and stereotypic behaviors, as well as by social impairment, attention, cognitive, and learning defects. ASDs present in early childhood and their prevalence has increased significantly to 1/150 children. Despite a number of theories, the actual reasons for this increase are still not clear. There is no reliable screening test, and no definite pathogenesis or curative therapy. Consequently, there is a major gap hampering development of effective treatments.

OBJECTIVE

To review recent publications on ASDs pathogenesis and treatment with emphasis on neuroimmune processes and new therapeutic approaches.

METHODS

Mostly original papers (450) on epidemiology, possible pathogenesis or treatment of ASDs in Medline from 1990 to May 2009 were reviewed. All authors contributed to this review.

RESULTS/CONCLUSION

Increased oxidative stress and immune dysregulation are present in ASDs. Mast-cell activation may contribute to gut-blood-brain barrier disruption and brain inflammation. No effective treatments have emerged. Well-designed clinical trials with nonpsychotropic drugs were few and ASD characteristics varied considerably, making conclusions difficult. Psychotropic drugs are often used for stereotypic and aggressive behaviors. Unique combinations with antioxidant and anti-inflammatory flavonoids hold promise. New potential translational research areas and possible treatments are suggested.

Autism Spectrum Disorders and Mastocytosis

Autism Spectrum Disorders (ASD) are diagnosed in early childhood and include Autism, Asperger's disorder and Pervasive neurodevelopmental disorder - not otherwise specified (PDD-NOS, or atypical autism). ASD are associated with varying degrees of dysfunctional communication and social skills, repetitive and stereotypic behaviors, as well as attention and learning disabilities. Most ASD patients also have food intolerance and other allergic symptomatology indicative of mast cell activation. The number of ASD cases have increased over the last decade to 1/100, but there is no definite pathogenesis or curative therapy. We report that the apparent prevalence of ASD in patients with mastocytosis, a rare disease occuring in 1/4,000 children and characterized by an increased number of hypersensitive mast cells in many organs, is about 1/10 or 10 times higher than the general population. A child with skin mastocytosis [urticaria pigmentosa, (UP)] and regressive autism is presented to illustrate the point. Allergic, infectious, neuroimmune and environmental triggers may activate mast cells to release vasoactive, inflammatory and neurotoxic molecules. These could disrupt the gut-blood-brain-barriers (BBB), and/or activate susceptibility genes, thus contributing to brain inflammation and ASD.

Flavonoids, a prenatal prophylaxis via targeting JAK2/STAT3 signaling to oppose IL-6/MIA associated autism

Maternal immune activation (MIA) can affect fetal brain development and thus behavior of young and adult offspring. Reports have shown that increased Interleukin-6 (IL-6) in the maternal serum plays a key role in altering fetal brain development, and may impair social behaviors in the offspring. Interestingly, these effects could be attenuated by blocking IL-6. The current study investigated the effects of luteolin, a citrus bioflavonoid, and its structural analog, diosmin, on IL-6 induced JAK2/STAT3 (Janus tyrosine kinase-2/signal transducer and activator of transcription-3) phosphorylation and signaling as well as behavioral phenotypes of MIA offspring. Luteolin and diosmin inhibited neuronal JAK2/STAT3 phosphorylation both in vitro and in vivo following IL-6 challenge as well as significantly diminishing behavioral deficits in social interaction. Importantly, our results showed that diosmin (10mg/kgday) was able to block the STAT3 signal pathway; significantly opposing MIA-induced abnormal behavior and neuropathological abnormalities in MIA/adult offspring. Diosmin's molecular inhibition of JAK2/STAT3 pathway may underlie the attenuation of abnormal social interaction in IL-6/MIA adult offspring.

A review of the fetal brain cytokine imbalance hypothesis of schizophrenia

Maternal infection during pregnancy increases the risk of schizophrenia and other brain disorders of neurodevelopmental origin in the offspring. A multitude of infectious agents seem to be involved in this association. Therefore, it has been proposed that factors common to the immune response to a wide variety of bacterial and viral pathogens may be the critical link between prenatal infection and postnatal brain and behavioral pathology. More specifically, it has been suggested that the maternal induction of pro-inflammatory cytokines may mediate the neurodevelopmental effects of maternal infections. Here, we review recent findings from in vitro and in vivo investigations supporting this hypothesis and further emphasize the influence of enhanced anti-inflammatory cytokine signaling on early brain development. Disruption of the fetal brain balance between pro- and anti-inflammatory cytokine signaling may thus represent a key mechanism involved in the precipitation of schizophrenia-related pathology following prenatal maternal infection and innate immune imbalances.

Animal models of autism spectrum disorders: information for neurotoxicologists

Recent findings derived from large-scale datasets and biobanks link multiple genes to autism spectrum disorders. Consequently, novel rodent mutants with deletions, truncations and in some cases, overexpression of these candidate genes have been developed and studied both behaviorally and biologically. At the Annual Neurotoxicology Meeting in Rochester, NY in October of 2008, a symposium of clinicians and basic scientists gathered to present the behavioral features of autism, as well as strategies to model those behavioral features in mice and primates. The aim of the symposium was to provide researchers with up-to-date information on both the genetics of autism and how they are used in differing in vivo and in vitro animal models as well as to provide a background on the environmental exposures being tested on several animal models. In addition, researchers utilizing complementary approaches, presented on cell culture, in vitro or more basic models, which target neurobiological mechanisms, including Drosophila. Following the presentation, a panel convened to explore the opportunities and challenges of using model systems to investigate genetic and environment interactions in autism spectrum disorders. The following paper represents a summary of each presentation, as well as the discussion that followed at the end of the symposium.

Effects of prenatal immune activation on hippocampal neurogenesis in the rat

Maternal infection during pregnancy has been associated with an increased risk for the development of schizophrenia, a disorder characterized by abnormalities in hippocampal morphology and function. Neurogenesis occurs in the hippocampus throughout development into adulthood and is believed to modulate hippocampal function. This study used a rat model in which bacterial endotoxin, lipopolysaccharide (LPS), is administered to pregnant dams, to test if prenatal immune activation has acute and/or long term effects on various phases of neurogenesis (proliferation, survival, differentiation) in the hippocampal dentate gyrus of offspring. When LPS was administered to dams on gestation days (GD) 15 and 16, there was decreased proliferation of dentate cells at postnatal day (PD) 14 and decreased survival of cells generated at PD14 in offspring. When prenatal exposure to LPS was later in pregnancy (GD 18 and 19), offspring showed decreased survival of cells generated both at the time of LPS exposure and at PD14. There was no change in cell proliferation or survival in adult offspring at PD60, with prenatal LPS exposure. Co-administration of the cyclo-oxygenase inhibitor, ibuprofen (IBU), together with prenatal LPS on GD 15 and 16, was unable to prevent the deficit in neuronal survival at PD14. IBU blocked LPS-induced fever but did not block LPS-induced increases in plasma cytokines and corticosterone in the pregnant dam. This indicates that deficits in neurogenesis caused by prenatal LPS are not mediated by LPS-induced fever or eicosanoid induction, but could be mediated by LPS-induced increases in maternal cytokines or corticosterone.

Does schizophrenia arise from oxidative dysregulation of parvalbumin-interneurons in the developing cortex?

An imbalance in the redox-state of the brain may be part of the underlying pathophysiology in schizophrenia. Inflammatory mediators, such as IL-6, which can tip the redox balance into a pro-oxidant state, have been consistently found to be altered in schizophrenia patients. However, the relationship of altered redox-state to altered brain functions observed in the disease has been unclear. Recent data from a pharmacological model of schizophrenia suggest that redox and inflammatory imbalances may be directly linked to the pathophysiology of the disease by alterations in fast-spiking interneurons. Repetitive adult exposure to the NMDA-R antagonist ketamine increases the levels of the proinflammatory cytokine interleukin-6 in brain which, through activation of the superoxide-producing enzyme NADPH oxidase (Nox2), leads to the loss of the GABAergic phenotype of PV-interneurons and to decreased inhibitory activity in prefrontal cortex. This effect is not observed after a single exposure to ketamine, suggesting that the first exposure to the NMDA-R antagonist primes the brain such that deleterious effects on PV-interneurons appear upon repetitive exposures. The effects of activation of the IL-6/Nox2 pathway on the PV-interneuronal system are reversible in the adult brain, but permanent in the developing cortex. The slow development of PV-interneurons, although essential for shaping of neuronal circuits during postnatal brain development, increases their vulnerability to deleterious insults that can permanently affect their maturational process. Thus, in individuals with genetic predisposition, the persistent activation of the IL-6/Nox2 pathway may be an environmental factor that tips the redox balance leading to schizophrenia symptoms in late adolescence and early adulthood.

Early-life programming of later-life brain and behavior: a critical role for the immune system

The immune system is well characterized for its critical role in host defense. Far beyond this limited role however, there is mounting evidence for the vital role the immune system plays within the brain, in both normal, “homeostatic” processes (e.g., sleep, metabolism, memory), as well as in pathology, when the dysregulation of immune molecules may occur. This recognition is especially critical in the area of brain development. Microglia and astrocytes, the primary immunocompetent cells of the CNS, are involved in every major aspect of brain development and function, including synaptogenesis, apoptosis, and angiogenesis. Cytokines such as tumor necrosis factor (TNF)α, interleukin [IL]-1β, and IL-6 are produced by glia within the CNS, and are implicated in synaptic formation and scaling, long-term potentiation, and neurogenesis. Importantly, cytokines are involved in both injury and repair, and the conditions underlying these distinct outcomes are under intense investigation and debate. Evidence from both animal and human studies implicates the immune system in a number of disorders with known or suspected developmental origins, including schizophrenia, anxiety/depression, and cognitive dysfunction. We review the evidence that infection during the perinatal period of life acts as a vulnerability factor for later-life alterations in cytokine production, and marked changes in cognitive and affective behaviors throughout the remainder of the lifespan. We also discuss the hypothesis that long-term changes in brain glial cell function underlie this vulnerability.

Neonatal infection with neurotropic influenza A virus affects working memory and expression of type III Nrg1 in adult mice

Epidemiological studies suggest that early life infections may contribute to the development of psychiatric disorders characterized by cognitive deficits. Here, we studied the effects of a neonatal influenza A/WSN/33 virus infection on locomotor activity, working memory and emotional behavior in adult mice. In addition to wild type mice, immunodeficient (Tap1(-/-)) mice lacking functional CD8(+) T cells, were included in the study to model the potential influence of a genetic deficit relating to virus clearance. Three to four months after the infection, infected Tap1(-/-) mice, but not wild type mice, exhibited deficits in working memory as well as increased rearing activity and anxiety. In the medial prefrontal cortices of these infected Tap1(-/-) mice reduced levels of type III Nrg1 transcripts were observed supporting a role for neuregulin 1 signaling in neuronal circuits involved in working memory. Virus replication, distribution or clearance did not differ between the two genotypes. The lack of CD8(+) T cells, however, appeared to contribute to a more pronounced glia response in Tap1(-/-) than in wild type mice. Thus, the present study suggest that the risk of developing deficits in cognitive and emotional behavior following a CNS infection during brain development is influenced by genetic variation in genes involved in the immune response.

Prenatal immune challenge is an environmental risk factor for brain and behavior change relevant to schizophrenia: evidence from MRI in a mouse model

Objectives

Maternal infection during pregnancy increases risk of severe neuropsychiatric disorders, including schizophrenia and autism, in the offspring. The most consistent brain structural abnormality in patients with schizophrenia is enlarged lateral ventricles. However, it is unknown whether the aetiology of ventriculomegaly in schizophrenia involves prenatal infectious processes. The present experiments tested the hypothesis that there is a causal relationship between prenatal immune challenge and emergence of ventricular abnormalities relevant to schizophrenia in adulthood.

Method

We used an established mouse model of maternal immune activation (MIA) by the viral mimic PolyI:C administered in early (day 9) or late (day 17) gestation. Automated voxel-based morphometry mapped cerebrospinal fluid across the whole brain of adult offspring and the results were validated by manual region-of-interest tracing of the lateral ventricles. Parallel behavioral testing determined the existence of schizophrenia-related sensorimotor gating abnormalities.

Results

PolyI:C-induced immune activation, in early but not late gestation, caused marked enlargement of lateral ventricles in adulthood, without affecting total white and grey matter volumes. This early exposure disrupted sensorimotor gating, in the form of prepulse inhibition. Identical immune challenge in late gestation resulted in significant expansion of 4^th ventricle volume but did not disrupt sensorimotor gating.

Conclusions

Our results provide the first experimental evidence that prenatal immune activation is an environmental risk factor for adult ventricular enlargement relevant to schizophrenia. The data indicate immune-associated environmental insults targeting early foetal development may have more extensive neurodevelopmental impact than identical insults in late prenatal life.

Prostaglandins compromise basal forebrain cholinergic neuron differentiation and survival: action at EP1/3 receptors results in AIF-induced death

Activated microglia produce a factor or cocktail of factors that promotes cholinergic neuronal differentiation of undifferentiated precursors in the embryonic basal forebrain (BF) in vitro. To determine whether microglial prostaglandins mediate this action, microglia were stimulated in the presence of the cyclooxygenase inhibitor ibuprofen, and microglial conditioned medium (CM) was used to culture rat BF precursors at embryonic day 15. Choline acetyltransferase (ChAT) activity served as a measure of cholinergic differentiation. While inhibition of prostaglandin biosynthesis did not affect the ability of microglial CM to promote ChAT activity, treatment of microglia with prostaglandin E2 (PGE2) inhibited it. Agonists of E prostanoid receptors EP2 (butaprost) and EP1/3 (sulprostone) mimicked PGE2, while misoprostol (E1-4) actually enhanced the action of CM. PGE2 added directly to BF cultures together with microglial CM also inhibited ChAT activity. While BF cultures expressed all four prostanoid receptors, direct addition of sulprostone but not butaprost mimicked PGE2, suggesting that PGE2 engaged EP1/3 receptors in the BF. Neither PKA inhibition by H89 nor cAMP induction by forskolin or dibutyrl-cAMP altered the action of sulprostone. Sulprostone severely compromised ChAT activity, dendrite number, axonal length and axonal branching, but caspase inhibition did not restore these. However, sulprostone resulted in increased staining intensity and nuclear translocation of apoptosis-inducing factor (AIF) suggesting caspase-independent cell death. We have found that PGE2 action at microglial EP2 receptors inhibits the microglial production of the cholinergic differentiating cocktail, while action at neuronal EP3 receptors has a deleterious effect on cholinergic neurons causing neurite retraction and cell death.

Modeling cognitive endophenotypes of schizophrenia in mice

Schizophrenia is a complex mental disorder that is still characterized by its symptoms rather than by biological markers because we have only a limited knowledge of its underlying molecular basis. In the past two decades, however, technical advances in genetics and brain imaging have provided new insights into the biology of the disease. Based on these advances we are now in a position to develop animal models that can be used to test specific hypotheses of the disease and explore mechanisms of pathogenesis. Here, we consider some of the insights that have emerged from studying in mice the relationship between defined genetic and molecular alterations and the cognitive endophenotypes of schizophrenia.

Prenatal immune activation leads to multiple changes in basal neurotransmitter levels in the adult brain: implications for brain disorders of neurodevelopmental origin such as schizophrenia

Maternal infection during pregnancy enhances the offspring's risk for severe neuropsychiatric disorders in later life, including schizophrenia. Recent attempts to model this association in animals provided further experimental evidence for a causal relationship between in-utero immune challenge and the postnatal emergence of a wide spectrum of behavioural, pharmacological and neuroanatomical dysfunctions implicated in schizophrenia. However, it still remains unknown whether the prenatal infection-induced changes in brain and behavioural functions may be associated with multiple changes at the neurochemical level. Here, we tested this hypothesis in a recently established mouse model of viral-like infection. Pregnant dams on gestation day 9 were exposed to viral mimetic polyriboinosinic-polyribocytidilic acid (PolyI:C, 5 mg/kg i.v.) or vehicle treatment, and basal neurotransmitter levels were then compared in the adult brains of animals born to PolyI:C- or vehicle-treated mothers by high-performance liquid chromatography on post-mortem tissue. We found that prenatal immune activation significantly increased the levels of dopamine and its major metabolites in the lateral globus pallidus and prefrontal cortex, whilst at the same time it decreased serotonin and its metabolite in the hippocampus, nucleus accumbens and lateral globus pallidus. In addition, a specific reduction of the inhibitory amino acid taurine in the hippocampus was noted in prenatally PolyI:C-exposed offspring relative to controls, whereas central glutamate and gamma-aminobutyric acid (GABA) content was largely unaffected by prenatal immune activation. Our results thus confirm that maternal immunological stimulation during early/middle pregnancy is sufficient to induce long-term changes in multiple neurotransmitter levels in the brains of adult offspring. This further supports the possibility that infection-mediated interference with early fetal brain development may predispose the developing organism to the emergence of neurochemical imbalances in adulthood, which may be critically involved in the precipitation of adult behavioural and pharmacological abnormalities after prenatal immune challenge.

Is routine influenza immunization warranted in early pregnancy?

Routine influenza immunization is recommended for select groups because of their higher risk of serious influenza outcomes. Based on that benefit-risk framework, we assessed whether routine administration of trivalent inactivated influenza vaccine (TIV) is warranted in pregnancy, beginning in 1st trimester. Higher maternal mortality due to influenza was extensively described during the 1918 and 1957 pandemics, but epidemiologic evidence thereafter is limited to case reports and a single ecologic analysis during a single season. Significantly elevated rates of hospitalization have been reported with seasonal influenza beginning in 1st trimester among women with select comorbidities and during the 2nd half of normal pregnancy. TIV protection against serious outcomes in pregnant women has not yet been shown. Although harm has also not been shown, sample size to date is insufficient to assert TIV safety in 1st trimester. Benefit-risk analysis suggests influenza immunization may be warranted at any stage of pregnancy during certain pandemics and annually among women with select comorbidities. TIV may also be warranted to protect women against influenza-related hospitalization during the 2nd half of normal pregnancy. Evidence is otherwise insufficient to recommend routine TIV as the standard of practice for all healthy women beginning in early pregnancy.

Neonatal polyI:C treatment in mice results in schizophrenia-like behavioral and neurochemical abnormalities in adulthood

It has been reported that viral infection in the first and second trimesters of pregnancy in humans increases the risk of subsequently developing schizophrenia. To develop a mouse model of immune activation during the early postnatal period, neonatal ICR mice were repeatedly injected with polyriboinosinic-polyribocytidilic acid (polyI:C; an inducer of strong innate immune responses) for 5 days (postnatal day 2-6) which may correspond, in terms of brain development, to the early second trimester in human. Cognitive and emotional behavior as well as the extracellular level of glutamate in the hippocampus were analyzed at the age of 10-12 weeks old. PolyI:C-treated mice showed anxiety-like behavior, impairment of object recognition memory and social behavior, and sensorimotor gating deficits, as compared to the saline-treated control group. Depolarization-evoked glutamate release in the hippocampus was impaired in polyI:C-treated mice compared to saline-treated control mice. Furthermore, to investigate the effect of neonatal immune activation on the expression levels of schizophrenia-related genes, we analyzed mRNA levels in the hippocampus 2 and 24h after polyI:C treatment. No significant differences or only transient and marginal changes were observed between polyI:C-treated and saline-treated control mice in the expression levels of schizophrenia-related genes in the hippocampus.

Prenatal exposure to antibodies from mothers of children with autism produces neurobehavioral alterations: A pregnant dam mouse model

A pregnant mouse model was used to compare the effect of IgG, administered E13-E18, from mothers of children with autistic disorder (MCAD), to controls (simple- and IgG-) on behavioral testing in offspring. Mice, exposed in-utero to MCAD-IgG, as adolescents, were more active during the first ten minutes of central field novelty testing and, as adults, displayed anxiety-like behavior on a component of the elevated plus maze and had a greater magnitude of startle following acoustic stimulation. On a social interaction paradigm, adult mice had alterations of sociability. Pilot studies of immune markers in MCAD IgG-exposed embryonic brains suggest evidence of cytokine and glial activation. These studies demonstrate that the transplacental passage of IgG from MCAD is capable of inducing long-term behavioral consequences.

Preventable cases of autism: relationship between chronic infectious diseases and neurological outcome

There is evidence that chronic infections and the immune reactions associated with them may contribute to causing autism spectrum disorders. These infections include Babesia, Bartonella, Borrelia burgdorferi, Ehrlichia, Human herpesvirus-6, Chlamydia pneumoniae and Mycoplasma (in particular Mycoplasma fermentans). Maternal immune reactions to infections appear to adversely affect fetal brain development and possible pathophysiological mechanisms include both inflammatory cytokines, such as IL-6, and maternal autoantibodies to fetal neural tissue of the same kilodalton mass as those seen with B. burgdorferi and some other chronic infections. The timing of the infection and immune response is critical in determining the pathophysiology. It is advisable to evaluate women who are pregnant or planning on becoming pregnant for chronic infections, especially if they demonstrate symptoms of an infection or a systemic illness with persistent inflammatory symptoms. The mother and the newborn should be treated when indicated.

Preliminary evidence of the in vitro effects of BDE-47 on innate immune responses in children with autism spectrum disorders

Autism spectrum disorders (ASD) are complex neurodevelopmental disorders that manifest in childhood. Immune dysregulation and autoimmune reactivity may contribute to the etiology of ASD and are likely the result of both genetic and environmental susceptibilities. A common environmental contaminant, 2,2',4,4'-tetrabrominated biphenyl (BDE-47), was tested for differential effects on the immune response of peripheral blood mononuclear cells (PBMC) isolated from children with ASD (n=19) and age-matched typically developing controls (TD, n=18). PBMC were exposed in vitro to either 100 nM or 500 nM BDE-47, before challenge with bacterial lipopolysaccharide (LPS), an innate immune activator, with resultant cytokine production measured using the Luminex multiplex platform. The cytokine responses of LPS stimulated PBMC from ASD and TD subjects diverged in the presence of 100 nM BDE. For example, cells cultured from the TD group demonstrated significantly decreased levels of the cytokines IL-12p40, GM-CSF, IL-6, TNFalpha, and the chemokines MIP-1alpha and MIP-1beta following LPS stimulation of PBMC pretreated with 100 nM BDE-47 compared with samples treated with vehicle control (p<0.05). In contrast, cells cultured from subjects with ASD demonstrated an increased IL-1beta response to LPS (p=0.033) when pretreated with 100 nM BDE-47 compared with vehicle control. Preincubation with 500 nM BDE-47 significantly increased the stimulated release of the inflammatory chemokine IL-8 (p<0.04) in cells cultured from subjects with ASD but not in cells from TD controls. These data suggest that in vitro exposure of PBMC to BDE-47 affects cell cytokine production in a pediatric population. Moreover, PBMC from the ASD subjects were differentially affected when compared with the TD controls suggesting a biological basis for altered sensitivity to BDE-47 in the ASD population.

Beta2-microglobulin abnormalities in antipsychotic-naïve schizophrenia: evidence for immune pathogenesis

Studies examining immune dysfunction in schizophrenia have reported decreased type-1 T-helper cell specific immunity (Th1) and increased type-2 T-helper cell specific immunity (Th2) and related abnormalities in inflammatory system. Beta2-Microglobulin (beta2M) influences the development of dendritic cells, which play a significant role in regulating the differentiation of naive CD4+ T cells into Th1 or Th2 lineages. The present study examined serum beta2M in antipsychotic-naïve schizophrenia patients (n=43) in comparison with age, sex, handedness and socioeconomic status matched healthy controls (n=43). Serum beta2M was significantly higher in schizophrenia patients (1692.6+/-354.4 ng/mL) than healthy controls (1409.6+/-246.9 ng/mL) (t=4.3; p<0.0001). There was a significant positive correlation between beta2M level and total psychopathology score (r=0.32; p=0.035). These novel observations suggest that beta2M abnormalities might have a potential association with the pathogenesis of schizophrenia.

Activation of the maternal immune system alters cerebellar development in the offspring

A common pathological finding in autism is a localized deficit in Purkinje cells (PCs). Cerebellar abnormalities have also been reported in schizophrenia. Using a mouse model that exploits a known risk factor for these disorders, maternal infection, we asked if the offspring of pregnant mice given a mid-gestation respiratory infection have cerebellar pathology resembling that seen in these disorders. We also tested the effects of maternal immune activation in the absence of virus by injection of the synthetic dsRNA, poly(I:C). We infected pregnant mice with influenza on embryonic day 9.5 (E9.5), or injected poly(I:C) i.p. on E12.5, and assessed the linear density of PCs in the cerebellum of adult or postnatal day 11 (P11) offspring. To study granule cell migration, we also injected BrdU on P11. Adult offspring of influenza- or poly(I:C)-exposed mice display a localized deficit in PCs in lobule VII of the cerebellum, as do P11 offspring. Coincident with this are heterotopic PCs, as well as delayed migration of granule cells in lobules VI and VII. The cerebellar pathology observed in the offspring of influenza- or poly(I:C)-exposed mice is strikingly similar to that observed in autism. The poly(I:C) findings indicate that deficits are likely caused by the activation of the maternal immune system. Finally, our data suggest that cerebellar abnormalities occur during embryonic development, and may be an early deficit in autism and schizophrenia.

Effects of bisphenol-A and other endocrine disruptors compared with abnormalities of schizophrenia: an endocrine-disruption theory of schizophrenia

In recent years, numerous substances have been identified as so-called "endocrine disruptors" because exposure to them results in disruption of normal endocrine function with possible adverse health outcomes. The pathologic and behavioral abnormalities attributed to exposure to endocrine disruptors like bisphenol-A (BPA) have been studied in animals. Mental conditions ranging from cognitive impairment to autism have been linked to BPA exposure by more than one investigation. Concurrent with these developments in BPA research, schizophrenia research has continued to find evidence of possible endocrine or neuroendocrine involvement in the disease. Sufficient information now exists for a comparison of the neurotoxicological and behavioral pathology associated with exposure to BPA and other endocrine disruptors to the abnormalities observed in schizophrenia. This review summarizes these findings and proposes a theory of endocrine disruption, like that observed from BPA exposure, as a pathway of schizophrenia pathogenesis. The review shows similarities exist between the effects of exposure to BPA and other related chemicals with schizophrenia. These similarities can be observed in 11 broad categories of abnormality: physical development, brain anatomy, cellular anatomy, hormone function, neurotransmitters and receptors, proteins and factors, processes and substances, immunology, sexual development, social behaviors or physiological responses, and other behaviors. Some of these similarities are sexually dimorphic and support theories that sexual dimorphisms may be important to schizophrenia pathogenesis. Research recommendations for further elaboration of the theory are proposed.

Interleukin-6 mediates the increase in NADPH-oxidase in the ketamine model of schizophrenia

Adult exposure to NMDA receptor antagonists, such as ketamine, produces psychosis in humans, and exacerbates symptoms in schizophrenic patients. We recently showed that ketamine activates the innate immune enzyme NADPH-oxidase in brain, and that the superoxide produced leads to dysfunction of a subset of fast-spiking inhibitory interneurons expressing the calcium-binding protein parvalbumin (PV). Here we show that neuronal production of interleukin-6 (IL-6) is necessary and sufficient for ketamine-mediated activation of NADPH-oxidase in brain. Removal of IL-6 in neuronal cultures by anti-IL-6 blocking antibodies, or in vivo by use of IL-6-deficient mice, prevented the increase in superoxide by ketamine and rescued the interneurons. Accumulating evidence suggests that schizophrenia patients suffer from diminished antioxidant defenses, and a recent clinical trial showed that enhancing these defenses may ameliorate symptoms of the disease. Our results showing that ketamine-induced IL-6 is responsible for the activation of NADPH-oxidase in brain suggest that reducing brain levels of this cytokine may protect the GABAergic phenotype of fast-spiking PV-interneurons and thus attenuate the propsychotic effects of ketamine.

Altered growth factor signaling pathways as the basis of aberrant stem cell maturation in schizophrenia

In recent years evidence has accumulated that the activity of the signaling cascades of Neuregulin-1, Wnt, TGF-beta, BDNF-p75 and DISC1 is different between control subjects and patients with schizophrenia. These pathways are involved in embryonic and adult neurogenesis and neuronal maturation. A review of the clinical data indicates that in schizophrenia the Wnt pathway is most likely hypoactive, whereas the Nrg1-ErbB4, the TGF-beta- and the BDNF-p75-pathways are hyperactive. Haplo-insuffiency of the DISC1 gene is currently the best established schizophrenia risk factor. Preclinical experiments indicate that suppression of DISC1 signaling leads to accelerated dendrite development in neuronal stem cells, accelerated migration and aberrant integration into the neuronal network. Other preclinical experiments show that increasing NRG1-, BDNF- and TGF-beta signaling and decreasing Wnt signaling, also promotes adult neuronal differentiation and migration. Thus deviations in these pathways detected in schizophrenia could contribute to premature neuronal differentiation, accelerated migration and inappropriate insertion into the neuronal network. Initial clinical findings are confirmatory: neuronal stem cells isolated from nasal biopsies from schizophrenia patients display signs of accelerated development, whilst increased erosion of telomeres and bone age provide further support for accelerated cell maturation in schizophrenia.

Deficient maternal care resulting from immunological stress during pregnancy is associated with a sex-dependent enhancement of conditioned fear in the offspring

Activation of maternal stress response systems during pregnancy has been associated with altered postpartum maternal care and subsequent abnormalities in the offspring’s brain and behavioral development. It remains unknown, however, whether similar effects may be induced by exposure to immunological stress during pregnancy. The present study was designed to address this issue in a mouse model of prenatal immune activation by the viral mimic polyriboinosinic–polyribocytidilic acid (PolyI:C). Pregnant mice were exposed to PolyI:C-induced immune challenge or sham treatment, and offspring born to PolyI:C- and sham-treated dams were simultaneously cross-fostered to surrogate rearing mothers, which had either experienced inflammatory or vehicle treatment during pregnancy. We evaluated the effects of the maternal immunological manipulation on postpartum maternal behavior, and we assessed the prenatal and postnatal maternal influences on anxiety- and fear-related behavior in the offspring at the peri-adolescent and adult stage of development. We found that PolyI:C treatment during pregnancy led to changes in postpartum maternal behavior in the form of reduced pup licking/grooming and increased nest building activity. Furthermore, the adoption of neonates by surrogate rearing mothers, which had experienced PolyI:C-induced immunological stress during pregnancy, led to enhanced conditioned fear in the peri-adolescent and adult offspring, an effect that was exclusively seen in female but not male subjects. Unconditioned (innate) anxiety-related behavior as assessed in the elevated plus maze and open field explorations tests were not affected by the prenatal and postnatal manipulations. Our results thus highlight that being raised by gestationally immune-challenged surrogate mothers increases the vulnerability for specific forms of fear-related behavioral pathology in later life, and that this association may be mediated by deficits in postpartum maternal care. This may have important implications for the identification and characterization of early-life risk factors involved in the developmental etiology of fear-related neuropsychiatric disorders.

Gene-environment interaction and covariation in schizophrenia: the role of obstetric complications

While genetic factors account for a significant proportion of liability to schizophrenia, a body of evidence attests to a significant environmental contribution. Understanding the mechanisms through which genetic and environmental factors coalesce in influencing schizophrenia is critical for elucidating the pathways underlying psychotic illness and for developing primary prevention strategies. Although obstetric complications (OCs) remain among the most well-documented environmental indicators of risk for schizophrenia, the pathogenic role they play in the etiology of schizophrenia continues to remain poorly understood. A question of major importance is do these factors result from a genetic diathesis to schizophrenia (as in gene-environment covariation), act additively or interactively with predisposing genes for the disorder in influencing disease risk, or independently cause disease onset? In this review, we evaluate 3 classes of OCs commonly related to schizophrenia including hypoxia-associated OCs, maternal infection during pregnancy, and maternal stress during pregnancy. In addition, we discuss several mechanisms by which OCs impact on genetically susceptible brain regions, increasing constitutional vulnerability to neuromaturational events and stressors later in life (ie, adolescence), which may in turn contribute to triggering psychosis.

Fluctuation of latent inhibition along the estrous cycle in the rat: modeling the cyclicity of symptoms in schizophrenic women?

Latent inhibition (LI) is a cross-species selective attention phenomenon manifested as poorer conditioning of stimuli that had been experienced as irrelevant prior to conditioning. Disruption of LI by pro-psychotic agents such as amphetamine and its restoration by antipsychotic drugs (APDs) is a well-established model of psychotic symptoms of schizophrenia. There is evidence that in schizophrenic women symptom severity and treatment response fluctuate along the menstrual cycle. Here we tested whether hormonal fluctuation along the estrous cycle in female rats (as determined indirectly via the cellular composition of the vaginal smears) would modulate the expression of LI and its response to APDs. The results showed that LI was seen if rats were in estrus during pre-exposure stage and in metestrus during the conditioning stage of the LI procedure (estrus-metestrus) but not along the remaining sequential phases of the cycle (metestrus-diestrus, diestrus-proestrus and proestrus-estrus). Additionally, the efficacy of typical and atypical APDs, haloperidol and clozapine, respectively, in restoring LI depended on estrous condition. Only LI disruption in proestrus-estrus exhibited sensitivity to both APDs, whereas LI disruption in the other two phases was alleviated by clozapine but not haloperidol. Our results show for the first time that both the expression of LI and its sensitivity to APDs are modulated along the estrous cycle, consistent with fluctuations in psychotic symptoms and response to APDs seen along women's menstrual cycle. Importantly, the results indicate that although both low and high levels of hormones may give rise to psychotic-like behavior as manifested in LI loss, the pro-psychotic state associated with low hormonal level is more severe due to reduced sensitivity to typical APDs. The latter constellation may mimic states of increased vulnerability to psychosis coupled with reduced treatment response documented in schizophrenic women during periods associated with low levels of hormones.

Prenatal protein deprivation alters dopamine-mediated behaviors and dopaminergic and glutamatergic receptor binding

Epidemiological evidence indicates that prenatal nutritional deprivation may increase the risk of schizophrenia. The goal of these studies was to use an animal model to examine the effects of prenatal protein deprivation on behaviors and receptor binding with relevance to schizophrenia. We report that prenatally protein deprived (PD) female rats showed an increased stereotypic response to apomorphine and an increased locomotor response to amphetamine in adulthood. These differences were not observed during puberty. No changes in haloperidol-induced catalepsy or MK-801-induced locomotion were seen following PD. In addition, PD female rats showed increased (3)H-MK-801 binding in the striatum and hippocampus, but not in the cortex. PD female rats also showed increased (3)H-haloperidol binding and decreased dopamine transporter binding in striatum. No statistically significant changes in behavior or receptor binding were found in PD males with the exception of increased (3)H-MK-801 binding in cortex. This animal model may be useful to explore the mechanisms by which prenatal nutritional deficiency enhances risk for schizophrenia in humans and may also have implications for developmental processes leading to differential sensitivity to drugs of abuse.

Potential for early-life immune insult including developmental immunotoxicity in autism and autism spectrum disorders: focus on critical windows of immune vulnerability

Early-life immune insults (ELII) including xenobiotic-induced developmental immunotoxicity (DIT) are important factors in childhood and adult chronic diseases. However, prenatal and perinatal environmentally induced immune alterations have yet to be considered in depth in the context of autism and autism spectrum disorders (ASDs). Numerous factors produce early-life-induced immune dysfunction in offspring, including exposure to xenobiotics, maternal infections, and other prenatal-neonatal stressors. Early life sensitivity to ELII, including DIT, results from the heightened vulnerability of the developing immune system to disruption and the serious nature of the adverse outcomes arising after disruption of one-time immune maturational events. The resulting health risks extend beyond infectious diseases, cancer, allergy, and autoimmunity to include pathologies of the neurological, reproductive, and endocrine systems. Because these changes may include misregulation of resident inflammatory myelomonocytic cells in tissues such as the brain, they are a potential concern in cases of prenatal-neonatal brain pathologies and neurobehavioral deficits. Autism and ASDs are chronic developmental neurobehavioral disorders that are on the rise in the United States with prenatal and perinatal environmental factors suspected as contributors to this increase. Evidence for an association between environmentally associated childhood immune dysfunction and ASDs suggests that ELII and DIT may contribute to these conditions. However, it is not known if this linkage is directly associated with the brain pathologies or represents a separate (or secondary) outcome. This review considers the known features of ELII and DIT and how they may provide important clues to prenatal brain inflammation and the risk of autism and ASDs.