Animal models of gene-environment interaction in schizophrenia: A dimensional perspective

The 3-hit animal models of schizophrenia: Improving strategy to decipher and treat the disease?

Schizophrenia is a complex disease related to combination and interactions between genetic and environmental factors, with an epigenetic influence. After the development of the first mono-factorial animal models of schizophrenia (1-hit), that reproduced patterns of either positive, negative and/or cognitive symptoms, more complex models combining two factors (2-hit) have been developed to better fit with the multifactorial etiology of the disease. In the two past decades, a new way to design animal models of schizophrenia have emerged by adding a third hit (3-hit). This review aims to discuss the relevance of the risk factors chosen for the tuning of the 3-hit animal models, as well as the validities measurements and their contribution to schizophrenia understanding. We intended to establish a comprehensive overview to help in the choice of factors for the design of multiple-hit animal models of schizophrenia.

Modeling psychotic disorders: Environment x environment interaction

Schizophrenia is a major psychotic disorder with multifactorial etiology that includes interactions between genetic vulnerability and environmental risk factors. In addition, interplay of multiple environmental adversities affects neurodevelopment and may increase the individual risk of developing schizophrenia. Consistent with the two-hit hypothesis of schizophrenia, we review rodent models that combine maternal immune activation as the first hit with other adverse environmental exposures as the second hit. We discuss the strengths and pitfalls of the current animal models of environment x environment interplay and propose some future directions to advance the field.

The herbicides glyphosate and glufosinate and the cyanotoxin β-N-methylamino-l-alanine induce long-term motor disorders following postnatal exposure: the importance of prior asymptomatic maternal inflammatory sensitization

Background

Prenatal maternal immune activation (MIA) and/or perinatal exposure to various xenobiotics have been identified as risk factors for neurological disorders, including neurodegenerative diseases. Epidemiological data suggest an association between early multi-exposures to various insults and neuropathologies. The "multiple-hit hypothesis" assumes that prenatal inflammation makes the brain more susceptible to subsequent exposure to several kinds of neurotoxins. To explore this hypothesis and its pathological consequences, a behavioral longitudinal procedure was performed after prenatal sensitization and postnatal exposure to low doses of pollutants.

Methods

Maternal exposure to an acute immune challenge (first hit) was induced by an asymptomatic lipopolysaccharide (LPS) dose (0.008 mg/kg) in mice. This sensitization was followed by exposing the offspring to environmental chemicals (second hit) postnatally, by the oral route. The chemicals used were low doses of the cyanotoxin β-N-methylamino-l-alanine (BMAA; 50 mg/kg), the herbicide glufosinate ammonium (GLA; 0.2 mg/kg) or the pesticide glyphosate (GLY; 5 mg/kg). After assessing maternal parameters, a longitudinal behavioral assessment was carried out on the offspring in order to evaluate motor and emotional abilities in adolescence and adulthood.

Results

We showed that the low LPS immune challenge was an asymptomatic MIA. Even though a significant increase in systemic pro-inflammatory cytokines was detected in the dams, no maternal behavioral defects were observed. In addition, as shown by rotarod assays and open field tests, this prenatal LPS administration alone did not show any behavioral disruption in offspring. Interestingly, our data showed that offspring subjected to both MIA and post-natal BMAA or GLA exposure displayed motor and anxiety behavioral impairments during adolescence and adulthood. However, this synergistic effect was not observed in the GLY-exposed offspring.

Conclusion

These data demonstrated that prenatal and asymptomatic immune sensitization represents a priming effect to subsequent exposure to low doses of pollutants. These double hits act in synergy to induce motor neuron disease-related phenotypes in offspring. Thus, our data strongly emphasize that multiple exposures for developmental neurotoxicity regulatory assessment must be considered. This work paves the way for future studies aiming at deciphering cellular pathways involved in these sensitization processes.

Neurobehavioral Profiles of Six Genetically-based Rat Models of Schizophrenia- related Symptoms

Schizophrenia is a chronic and severe mental disorder with high heterogeneity in its symptoms clusters. The effectiveness of drug treatments for the disorder is far from satisfactory. It is widely accepted that research with valid animal models is essential if we aim at understanding its genetic/ neurobiological mechanisms and finding more effective treatments. The present article presents an overview of six genetically-based (selectively-bred) rat models/strains, which exhibit neurobehavioral schizophrenia-relevant features, i.e., the Apomorphine-susceptible (APO-SUS) rats, the Low-prepulse inhibition rats, the Brattleboro (BRAT) rats, the Spontaneously Hypertensive rats (SHR), the Wisket rats and the Roman High-Avoidance (RHA) rats. Strikingly, all the strains display impairments in prepulse inhibition of the startle response (PPI), which remarkably, in most cases are associated with novelty-induced hyperlocomotion, deficits of social behavior, impairment of latent inhibition and cognitive flexibility, or signs of impaired prefrontal cortex (PFC) function. However, only three of the strains share PPI deficits and dopaminergic (DAergic) psychostimulant-induced hyperlocomotion (together with prefrontal cortex dysfunction in two models, the APO-SUS and RHA), which points out that alterations of the mesolimbic DAergic circuit are a schizophrenia-linked trait that not all models reproduce, but it characterizes some strains that can be valid models of schizophrenia-relevant features and drug-addiction vulnerability (and thus, dual diagnosis). We conclude by putting the research based on these genetically-selected rat models in the context of the Research Domain Criteria (RDoC) framework, suggesting that RDoC-oriented research programs using selectively-bred strains might help to accelerate progress in the various aspects of the schizophrenia-related research agenda.

The critical periods of cerebral plasticity: A key aspect in a dialog between psychoanalysis and neuroscience centered on the psychopathology of schizophrenia

Through research into the molecular and cellular mechanisms that occur during critical periods, recent experimental neurobiological data have brought to light the importance of early childhood. These have demonstrated that childhood and early environmental stimuli play a part not only in our subjective construction, but also in brain development; thus, confirming Freud's intuition regarding the central role of childhood and early experiences of the environment in our psychological development and our subjective outcomes. "Critical periods" of cerebral development represent temporal windows that mark favorable, but also circumscribed, moments in developmental cerebral plasticity. They also vary between different cortical areas. There are, therefore, strictly defined temporal periods for learning language, music, etc., after which this learning becomes more difficult, or even impossible, to acquire. Now, research into these critical periods can be seen as having a significant part to play in the interdisciplinary dialog between psychoanalysis and neurosciences with regard to the role of early experiences in the etiology of some psychopathological conditions. Research into the cellular and molecular mechanisms controlling the onset and end of these critical periods, notably controlled by the maturation of parvalbumin-expressing basket cells, have brought to light the presence of anomalies in the maturation of these neurons in patients with schizophrenia. Starting from these findings we propose revisiting the psychoanalytic theories on the etiology of psychosis from an interdisciplinary perspective. Our study works from the observation, common to both psychoanalysis and neurosciences, that experience leaves a trace; be it a "psychic" or a "synaptic" trace. Thus, we develop a hypothesis for an "absence of trace" in psychosis; reexamining psychosis through the prism of the biological theory of critical periods in plasticity.

Sources and Translational Relevance of Heterogeneity in Maternal Immune Activation Models

The epidemiological literature reporting increased risk for neurodevelopmental and psychiatric disorders after prenatal exposure to maternal immune activation (MIA) is still evolving, and so are the attempts to model this association in animals. Epidemiological studies of MIA offer the advantage of directly evaluating human populations but are often limited in their ability to uncover pathogenic mechanisms. Animal models, on the other hand, are limited in their generalizability to psychiatric disorders but have made significant strides toward discovering causal relationships and biological pathways between MIA and neurobiological phenotypes. Like in any other model system, both planned and unplanned sources of variability exist in animal models of MIA. Therefore, the design, implementation, and interpretation of MIA models warrant a careful consideration of these sources, so that appropriate strategies can be developed to handle them satisfactorily. While every research group may have its own strategy to this aim, it is essential to report the methodological details of the chosen MIA model in order to enhance the transparency and comparability of models across research laboratories. Even though it poses a challenge for attempts to compare experimental findings across laboratories, variability does not undermine the utility of MIA models for translational research. In fact, variability and heterogenous outcomes in MIA models offer unique opportunities for new discoveries and developments in this field, including the identification of disease pathways and molecular mechanisms determining susceptibility and resilience to MIA. This review summarizes the most important sources of variability in animal models of MIA and discusses how model variability can be used to investigate neurobiological and immunological factors causing phenotypic heterogeneity in offspring exposed to MIA.

Neurotrophic factors, childhood trauma and psychiatric disorders: A systematic review of genetic, biochemical, cognitive and imaging studies to identify potential biomarkers

BACKGROUND

Exposure to traumatic experience represents one of the key environmental factors influencing the risk for several psychiatric disorders, in particular when suffered during childhood, a critical period for brain development, characterized by a high level of neuroplasticity. Abnormalities affecting neurotrophic factors might play a fundamental role in the link between childhood trauma (CT) and early life stress (ELS) and psychiatric disorders.

METHODS

A systematic review was conducted, considering genetic, biochemical and expression studies along with cognitive and brain structure imaging investigations, based on PubMed and Web of Science databases (available up until November 2021), to identify potential neuroplasticity related biomarkers associated both with CT/ELS and psychiatric disorders. The search was followed by data abstraction and study quality assessment (Newcastle-Ottawa Scale).

RESULTS

103 studies met our eligibility criteria. Among them, 65 were available for genetic, 30 for biochemical and 3 for mRNA data; 45 findings were linked to specific symptomatology/pathologies, 16 with various cognitive functions, 19 with different brain areas, 6 on methylation and 36 performed on control subjects for the Brain Derived Neurotrophic Factor (BDNF); whereas 4 expression/biochemical studies covered Neurotrophin 4 (NT-4), Vascular Endothelium Growth Factor (VEGF), Epidermal Growth Factor (EGF), Fibroblast Growth Factor (FGF), and Transforming Growth Factor β1 (TGF-β1).

LIMITATIONS

Heterogeneity of assessments (biological, psychological, of symptomatology, and CT/ELS), age range and ethnicity of samples for BDNF studies; limited studies for other neurotrophins.

CONCLUSIONS

Results support the key role of BDNF (in form of Met allele) as biomarker, both at genetic and biochemical level, in mediating the effect of CT/ELS in psychiatric disorders, passing through specific cognitive functions and specific brain region architecture.

Virus-Induced Maternal Immune Activation as an Environmental Factor in the Etiology of Autism and Schizophrenia

Maternal immune activation (MIA) is mediated by activation of inflammatory pathways resulting in increased levels of cytokines and chemokines that cross the placental and blood-brain barriers altering fetal neural development. Maternal viral infection is one of the most well-known causes for immune activation in pregnant women. MIA and immune abnormalities are key players in the etiology of developmental conditions such as autism, schizophrenia, ADHD, and depression. Experimental evidence implicating MIA in with different effects in the offspring is complex. For decades, scientists have relied on either MIA models or human epidemiological data or a combination of both. MIA models are generated using infection/pathogenic agents to induce an immunological reaction in rodents and monitor the effects. Human epidemiological studies investigate a link between maternal infection and/or high levels of cytokines in pregnant mothers and the likelihood of developing conditions. In this review, we discuss the importance of understanding the relationship between virus-mediated MIA and neurodevelopmental conditions, focusing on autism and schizophrenia. We further discuss the different methods of studying MIA and their limitations and focus on the different factors contributing to MIA heterogeneity.

Dysbindin-1, BDNF, and GABAergic Transmission in Schizophrenia

Schizophrenia is a psychiatric disorder characterized by hallucinations, anhedonia, disordered thinking, and cognitive impairments. Both genetic and environmental factors contribute to schizophrenia. Dysbindin-1 (DTNBP1) and brain-derived neurotrophic factor (BDNF) are both genetic factors associated with schizophrenia. Mice lacking Dtnbp1 showed behavioral deficits similar to human patients suffering from schizophrenia. DTNBP1 plays important functions in synapse formation and maintenance, receptor trafficking, and neurotransmitter release. DTNBP1 is co-assembled with 7 other proteins into a large protein complex, known as the biogenesis of lysosome-related organelles complex-1 (BLOC-1). Large dense-core vesicles (LDCVs) are involved in the secretion of hormones and neuropeptides, including BDNF. BDNF plays important roles in neuronal development, survival, and synaptic plasticity. BDNF is also critical in maintaining GABAergic inhibitory transmission in the brain. Two studies independently showed that DTNBP1 mediated activity-dependent BDNF secretion to maintain inhibitory transmission. Imbalance of excitatory and inhibitory neural activities is thought to contribute to schizophrenia. In this mini-review, we will discuss a potential pathogenetic mechanism for schizophrenia involving DTNBP1, BDNF, and inhibitory transmission. We will also discuss how these processes are interrelated and associated with a higher risk of schizophrenia development.

The Perspectives of Early Diagnosis of Schizophrenia Through the Detection of Epigenomics-Based Biomarkers in iPSC-Derived Neurons

The lack of early diagnostic biomarkers for schizophrenia greatly limits treatment options that deliver therapeutic agents to affected cells at a timely manner. While previous schizophrenia biomarker research has identified various biological signals that are correlated with certain diseases, their reliability and practicality as an early diagnostic tool remains unclear. In this article, we discuss the use of atypical epigenetic and/or consequent transcriptional alterations (ETAs) as biomarkers of early-stage schizophrenia. Furthermore, we review the viability of discovering and applying these biomarkers through the use of cutting-edge technologies such as human induced pluripotent stem cell (iPSC)-derived neurons, brain models, and single-cell level analyses.

Neurobehavioral and neurodevelopmental profiles of a heuristic genetic model of differential schizophrenia- and addiction-relevant features: The RHA vs. RLA rats

The Roman High- (RHA) and Low-(RLA) avoidance rat lines/strains were generated through bidirectional selective breeding for rapid (RHA) vs. extremely poor (RLA) two-way active avoidance acquisition. Compared with RLAs and other rat strains/stocks, RHAs are characterized by increased impulsivity, deficits in social behavior, novelty-induced hyper-locomotion, impaired attentional/cognitive abilities, vulnerability to psychostimulant sensitization and drug addiction. RHA rats also exhibit decreased function of the prefrontal cortex (PFC) and hippocampus, increased functional activity of the mesolimbic dopamine system and a dramatic deficit of central metabotropic glutamate-2 (mGlu2) receptors (due to a stop codon mutation at cysteine 407 in Grm2 -cys407*-), along with increased density of 5-HT2A receptors in the PFC, alterations of several synaptic markers and increased density of pyramidal "thin" (immature) dendrític spines in the PFC. These characteristics suggest an immature brain of RHA rats, and are reminiscent of schizophrenia features like hypofrontality and disruption of the excitation/inhibition cortical balance. RHA rats represent a promising heuristic model of neurodevelopmental schizophrenia-relevant features and comorbidity with drug addiction vulnerability.

Association between TLR2 polymorphisms (- 196-174 Ins/Del, R677W, R753Q, and P631H) and schizophrenia in a Tunisian population

Since immune dysregulation has been well studied in schizophrenia pathophysiology, recent studies showed a potent role of TLR2 in neuroinflammation process underlying schizophrenia pathogenesis. However, the genetic predisposition is still unclear. Thus, we hypothesized that TLR2 polymorphisms - 196-174 Ins/Del (rs111200466), R753Q (rs5743708), R677W (rs121917864), and P631H (rs5743704) could be involved in schizophrenia predisposition. A case-control study was performed on a Tunisian population composed of 250 healthy controls and 250 patients genotyped by PCR-RFLP. Genotype and allele distribution were evaluated with sex, schizophrenia subtypes, and other clinical features. We also assessed a haplotype analysis for TLR2 polymorphisms with schizophrenia. Our results showed higher ins/del genotype frequency in healthy women compared to patients (p = 0.006; OR = 0.2). In the other hand, logistic regression showed higher ins/del genotype frequency in controls compared to paranoid patients (p = 0.05; OR = 0.48, adjusted). Frequencies of CT and T allele of R677W were significantly higher in patients compared to controls (p < 10^-4, OR = 10.39; p < 10^-4, OR = 4, adjusted, respectively). R753Q polymorphism was exclusively detected in patients (GA + AA = 2.5%) particularly in men with disorganized subtype. P631H did not show any association with schizophrenia. Finally, haplotype analysis showed that InsGTC and delGTC were associated with higher risk of schizophrenia (p = 0.0001, OR = 8.58; p = 0.04, OR = 5.01, respectively). In the Tunisian population, our results suggested that TLR2 R677W could be associated with susceptibility for schizophrenia, while - 196-174 Ins/Del suggested a trend of protection in women. Otherwise, R753Q could have an effect on schizophrenia especially for disorganized subgroup.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Long-Acting Risperidone Dual Control System: Preparation, Characterization and Evaluation In Vitro and In Vivo

Schizophrenia, a psychiatric disorder, requires long-term treatment; however, large fluctuations in blood drug concentration increase the risk of adverse reactions. We prepared a long-term risperidone (RIS) implantation system that can stabilize RIS release and established in-vitro and in-vivo evaluation systems. Cumulative release, drug loading, and entrapment efficiency were used as evaluation indicators to evaluate the effects of different pore formers, polymer ratios, porogen concentrations, and oil–water ratios on a RIS implant (RIS-IM). We also built a mathematical model to identify the optimized formulation by stepwise regression. We also assessed the crystalline changes, residual solvents, solubility and stability after sterilization, in-vivo polymer degradation, pharmacokinetics, and tissue inflammation in the case of the optimized formulation. The surface of the optimized RIS microspheres was small and hollow with 134.4 ± 3.5 µm particle size, 1.60 SPAN, 46.7% ± 2.3% implant drug loading, and 93.4% entrapment efficiency. The in-vitro dissolution behavior of RIS-IM had zero-order kinetics and stable blood concentration; no lag time was released for over three months. Furthermore, the RIS-IM was not only non-irritating to tissues but also had good biocompatibility and product stability. Long-acting RIS-IMs with microspheres and film coatings can provide a new avenue for treating schizophrenia.

Shedding light on the role of CX3CR1 in the pathogenesis of schizophrenia

Schizophrenia has a complex and heterogeneous molecular and clinical picture. Over the years of research on this disease, many factors have been suggested to contribute to its pathogenesis. Recently, the inflammatory processes have gained particular interest in the context of schizophrenia due to the increasing evidence from epidemiological, clinical and experimental studies. Within the immunological component, special attention has been brought to chemokines and their receptors. Among them, CX3C chemokine receptor 1 (CX3CR1), which belongs to the family of seven-transmembrane G protein-coupled receptors, and its cognate ligand (CX3CL1) constitute a unique system in the central nervous system. In the view of regulation of the brain homeostasis through immune response, as well as control of microglia reactivity, the CX3CL1–CX3CR1 system may represent an attractive target for further research and schizophrenia treatment. In the review, we described the general characteristics of the CX3CL1–CX3CR1 axis and the involvement of this signaling pathway in the physiological processes whose disruptions are reported to participate in mechanisms underlying schizophrenia. Furthermore, based on the available clinical and experimental data, we presented a guide to understanding the implication of the CX3CL1–CX3CR1 dysfunctions in the course of schizophrenia.

Functional Dysregulations in CA1 Hippocampal Networks of a 3-Hit Mouse Model of Schizophrenia

For a better translation from treatment designs of schizophrenia to clinical efficiency, there is a crucial need to refine preclinical animal models. In order to consider the multifactorial nature of the disorder, a new mouse model associating three factors (genetic susceptibility-partial deletion of the MAP6 gene, early-life stress-maternal separation, and pharmacological treatment-chronic Δ-9-tetrahydrocannabinol during adolescence) has recently been described. While this model depicts a schizophrenia-like phenotype, the neurobiological correlates remain unknown. Synaptic transmission and functional plasticity of the CA1 hippocampal region of male and female 3-hit mice were therefore investigated using electrophysiological recordings on the hippocampus slice. While basal excitatory transmission remained unaffected, NMDA receptor (NMDAr)-mediated long-term potentiation (LTP) triggered by theta-burst (TBS) but not by high-frequency (HFS) stimulation was impaired in 3-hit mice. Isolated NMDAr activation was not affected or even increased in female 3-hit mice, revealing a sexual dimorphism. Considering that the regulation of LTP is more prone to inhibitory tone if triggered by TBS than by HFS, the weaker potentiation in 3-hit mice suggests a deficiency of intrinsic GABA regulatory mechanisms. Indeed, NMDAr activation was increased by GABAA receptor blockade in wild-type but not in 3-hit mice. This electrophysiological study highlights dysregulations of functional properties and plasticity in hippocampal networks of 3-hit mice, one of the mechanisms suspected to contribute to the pathophysiology of schizophrenia. It also shows differences between males and females, supporting the sexual dimorphism observed in the disorder. Combined with the previously reported study, the present data reinforce the face validity of the 3-hit model that will help to consider new therapeutic strategies for psychosis.

Epigenetic Modifications in Schizophrenia and Related Disorders: Molecular Scars of Environmental Exposures and Source of Phenotypic Variability

Epigenetic modifications are increasingly recognized to play a role in the etiology and pathophysiology of schizophrenia and other psychiatric disorders with developmental origins. Here, we summarize clinical and preclinical findings of epigenetic alterations in schizophrenia and relevant disease models and discuss their putative origin. Recent findings suggest that certain schizophrenia risk loci can influence stochastic variation in gene expression through epigenetic processes, highlighting the intricate interaction between genetic and epigenetic control of neurodevelopmental trajectories. In addition, a substantial portion of epigenetic alterations in schizophrenia and related disorders may be acquired through environmental factors and may be manifested as molecular "scars." Some of these scars can influence brain functions throughout the entire lifespan and may even be transmitted across generations via epigenetic germline inheritance. Epigenetic modifications, whether caused by genetic or environmental factors, are plausible molecular sources of phenotypic heterogeneity and offer a target for therapeutic interventions. The further elucidation of epigenetic modifications thus may increase our knowledge regarding schizophrenia's heterogeneous etiology and pathophysiology and, in the long term, may advance personalized treatments through the use of biomarker-guided epigenetic interventions.

Behavioral, neuroanatomical, and molecular correlates of resilience and susceptibility to maternal immune activation

Infectious or noninfectious maternal immune activation (MIA) is an environmental risk factor for psychiatric and neurological disorders with neurodevelopmental etiologies. Whilst there is increasing evidence for significant health consequences, the effects of MIA on the offspring appear to be variable. Here, we aimed to identify and characterize subgroups of isogenic mouse offspring exposed to identical MIA, which was induced in C57BL6/N mice by administration of the viral mimetic, poly(I:C), on gestation day 12. Cluster analysis of behavioral data obtained from a first cohort containing >150 MIA and control offspring revealed that MIA offspring could be stratified into distinct subgroups that were characterized by the presence or absence of multiple behavioral dysfunctions. The two subgroups also differed in terms of their transcriptional profiles in cortical and subcortical brain regions and brain networks of structural covariance, as measured by ex vivo structural magnetic resonance imaging (MRI). In a second, independent cohort containing 50 MIA and control offspring, we identified a subgroup of MIA offspring that displayed elevated peripheral production of innate inflammatory cytokines, including IL-1β, IL-6, and TNF-α, in adulthood. This subgroup also showed significant impairments in social approach behavior and sensorimotor gating, whereas MIA offspring with a low inflammatory cytokine status did not. Taken together, our results highlight the existence of subgroups of MIA-exposed offspring that show dissociable behavioral, transcriptional, brain network, and immunological profiles even under conditions of genetic homogeneity. These data have relevance for advancing our understanding of the variable neurodevelopmental effects induced by MIA and for biomarker-guided approaches in preclinical psychiatric research.

A new 3-hit mouse model of schizophrenia built on genetic, early and late factors

Whether the etiology of schizophrenia remains unknown, its multifactorial aspect is conversely now well admitted. However, most preclinical models of the disease still rely on a mono-factorial construction and do not allow discover unequivocal treatments, particularly for negative and cognitive symptoms. The main interaction factors that have been implicated in schizophrenia are a genetic predisposition and unfavorable environmental factors. Here we propose a new animal model combining a genetic predisposition (1st hit: partial deletion of MAP-6 (microtubule-associated protein)) with an early postnatal stress (2nd hit: 24 h maternal separation at post-natal day 9), and a late cannabinoid exposure during adolescence (3rd hit: tetrahydrocannabinol THC from post-natal day 32 to 52; 8 mg/kg/day). The 2-hit mice displayed spatial memory deficits, decreased cortical thickness and fractional anisotropy of callosal fibers. The 3-hit mice were more severely affected as attested by supplementary deficits such a decrease in spontaneous activity, sociability-related behavior, working memory performances, an increase in anxiety-like behavior, a decrease in hippocampus volume together with impaired integrity of corpus callosum fibers (less axons, less myelin). Taken together, these results show that the new 3-hit model displays several landmarks mimicking negative and cognitive symptoms of schizophrenia, conferring a high relevance for research of new treatments. Moreover, this 3-hit model possesses a strong construct validity, which fits with gene x environment interactions hypothesis of schizophrenia. The 2-hit model, which associates maternal separation with THC exposure in wild-type mice gives a less severe phenotype, and could be useful for research on other forms of psychiatric diseases.

Innovative screening models for the discovery of new schizophrenia drug therapies: an integrated approach

Introduction: Schizophrenia is a severe psychiatric disorder affecting millions worldwide. However, available treatment options do not fully address the disease. Whereas current antipsychotics may control psychotic symptoms, they seem notoriously ineffective in improving negative and cognitive symptoms or in preventing functional decline. As the etiology of schizophrenia eludes us, the development of valid animal models for screening new drug targets appears to be a strenuous task.Areas covered: In this review, the authors present the key concepts that validate animal models of schizophrenia, as well as the different screening approaches for novel schizophrenia treatments. The models covered are either based on major neurotransmitter systems or neurodevelopmental, immune, and genetic approaches.Expert opinion: Sadly, due to inertia, research focuses on developing 'anti-psychotics', instead of 'anti-schizophrenia' drugs that would tackle the entire syndrome of schizophrenia. Whereas no perfect model may ever exist, combining different experimental designs may enhance validity, as the over-reliance on a single model is inappropriate. Multi-model approaches incorporating vulnerability, the 'two-hit' hypothesis, and endophenotypes offer a promise for developing new strategies for schizophrenia treatment. Forward and reverse translation between preclinical and clinical research will increase the probability of success and limit failures in drug development.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Involvement of NLRP3 inflammasome in schizophrenia-like behaviour in young animals after maternal immune activation

OBJECTIVE

To evaluate the involvement of nod-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome in schizophrenia-like behaviour in young animals exposed to maternal immune activation (MIA).

METHODS

To this aim, on the 15th gestational day, the females received an injection of lipopolysaccharides. When the animals completed 7, 14 and 45 postnatal days, they were killed and the whole brain was dissected for biochemical analysis. Animals with 45 postnatal days were submitted to behavioural tests of locomotor activity, social interaction and stereotyped movements.

RESULTS

It was observed that the animals presented schizophrenia-like behaviour at 45 postnatal days associated with the increase of NLRP3 inflammasome expression and IL-1β levels on 7, 14 and 45 postnatal days.

CONCLUSION

This study shows that MIA may be associated with a schizophrenia-like behaviour. This behaviour can be induced to a neuroinflammatory profile in the brain. These evidences may base future studies on the relationship between neuroinflammation and psychiatric disorders.

Incorporating multiple sets of eQTL weights into gene-by-environment interaction analysis identifies novel susceptibility loci for pancreatic cancer

It is of great scientific interest to identify interactions between genetic variants and environmental exposures that may modify the risk of complex diseases. However, larger sample sizes are usually required to detect gene-by-environment interaction (G × E) than required to detect genetic main association effects. To boost the statistical power and improve the understanding of the underlying molecular mechanisms, we incorporate functional genomics information, specifically, expression quantitative trait loci (eQTLs), into a data-adaptive G × E test, called aGEw. This test adaptively chooses the best eQTL weights from multiple tissues and provides an extra layer of weighting at the genetic variant level. Extensive simulations show that the aGEw test can control the Type 1 error rate, and the power is resilient to the inclusion of neutral variants and noninformative external weights. We applied the proposed aGEw test to the Pancreatic Cancer Case-Control Consortium (discovery cohort of 3,585 cases and 3,482 controls) and the PanScan II genome-wide association study data (replication cohort of 2,021 cases and 2,105 controls) with smoking as the exposure of interest. Two novel putative smoking-related pancreatic cancer susceptibility genes, TRIP10 and KDM3A, were identified. The aGEw test is implemented in an R package aGE.

Childhood adversity and psychosis: a systematic review of bio-psycho-social mediators and moderators

The association between childhood adversity (CA) and psychosis has been extensively investigated in recent years. An increasing body of research has also focused on the mediating or moderating role of biological and psychological mechanisms, as well as other risk factors that might account for the link between CA and psychosis. We conducted a systematic search of the PsychINFO, Embase, Ovid, and Web of Science databases for original articles investigating the role of genetic vulnerabilities, environmental factors, psychological and psychopathological mechanisms in the association between CA and psychosis up to August 2019. We included studies with individuals at different stages of the psychosis continuum, from subclinical psychotic experiences to diagnosed disorders. From the 28 944 records identified, a total of 121 studies were included in this review. Only 26% of the studies identified met the criteria for methodological robustness. Overall, the current evidence suggests that CA may be associated with psychosis largely independently of genetic vulnerabilities. More consistent and robust evidence supports interaction between early and recent adversities, as well as the mediating role of attachment and mood symptoms, which is suggestive of an affective pathway between CA and psychosis across the continuum from subclinical experiences to diagnosable disorder. This review highlighted numerous methodological issues with the existing literature, including selection bias, heterogeneity of measurement instruments utilised, and lack of control for potential confounders. Future research should address these limitations to more accurately estimate mediation and moderation effects on the CA-psychosis association to inform the development of preventive interventions.

Assessment of coexisting psychosis and substance misuse: complexities, challenges and causality

Substance misuse worsens the prognosis for people suffering psychosis and places them at risk of being denied appropriate mental health service interventions. To increase the chances of its success, the plan of management for patients with coexisting psychosis and substance misuse should be based on a valid formulation of their problems, which in turn is dependent on the clinician having (a) a thorough understanding of the bidirectional and changing ways that substance use and mental illness symptoms can interact, (b) an awareness of their own biased implicit assumptions about causality in explaining these interactions and (c) a framework for assessment and formulation. This article addresses these three areas with reference to the evidence base and to clinical experience in a way that guides mental health clinicians in the assessment of patients with coexisting psychosis and substance misuse.

Are Circadian Disturbances a Core Pathophysiological Component of Schizophrenia?

Schizophrenia is a multifactorial disorder caused by a combination of genetic variations and exposure to environmental insults. Sleep and circadian rhythm disturbances are a prominent and ubiquitous feature of many psychiatric disorders, including schizophrenia. There is growing interest in uncovering the mechanistic link between schizophrenia and circadian rhythms, which may directly affect disorder outcomes. In this review, we explore the interaction between schizophrenia and circadian rhythms from 2 complementary angles. First, we review evidence that sleep and circadian rhythm disturbances constitute a fundamental component of schizophrenia, as supported by both human studies and animal models with genetic mutations related to schizophrenia. Second, we discuss the idea that circadian rhythm disruption interacts with existing risk factors for schizophrenia to promote schizophrenia-relevant behavioral and neurobiological abnormalities. Understanding the mechanistic link between schizophrenia and circadian rhythms will have implications for mitigating risk to the disorder and informing the development of circadian-based therapies.

Neurodevelopmental Factors in Schizophrenia

The onset of schizophrenia is usually in late adolescence or early adulthood. However, accumulating evidence has suggested that the disease condition is an outcome of gene-environment interactions that act in neural development during early life and adolescence. Some children who later develop schizophrenia have early developmental and educational and social challenges. Some patients with schizophrenia have an abundance of nonspecific neurologic soft signs and minor physical anomalies. Adolescence is a sensitive period of increased neuronal plasticity. It is important to consider early detection and intervention from the prodromal stage to early disease to prevent its devastating long-term consequences.

Can in utero Zika virus exposure be a risk factor for schizophrenia in the offspring?

Objectives: Schizophrenia is a severe psychiatric illness that has been purported to be causally related to in utero infection of neurotropic organisms. For obvious ethical reasons, this hypothesis has never been tested prospectively in humans. However, with the recent introduction of Zika virus into the New World offers the opportunity to test the hypothesis of infection in schizophrenia.Methods: This is a directed review examining the hypothesis. The literature relevant to Zika virus transmission in the New World, its biology and neurotropy is reviewed.Results: Zika virus has been associated with a wide variety of neural tube and neuroanatomical abnormalities. In its original range, Zika is only infrequently associated with congenital anomalies, but in the New World, where the majority of the population has not developed immunity, infections are associated with a wide range of neurologic abnormalities.Conclusions: The current outbreak of Zika virus in the Western Hemisphere, offers the opportunity to prospectively examine the congenital infection hypothesis of the pathogenesis of schizophrenia.

The Role of Zebrafish and Laboratory Rodents in Schizophrenia Research

Schizophrenia is a severe disorder characterized by positive, negative and cognitive symptoms, which are still not fully understood. The development of efficient antipsychotics requires animal models of a strong validity, therefore the aims of the article were to summarize the construct, face and predictive validity of schizophrenia models based on rodents and zebrafish, to compare the advantages and disadvantages of these models, and to propose future directions in schizophrenia modeling and indicate when it is reasonable to combine these models. The advantages of rodent models stem primarily from the high homology between rodent and human physiology, neurochemistry, brain morphology and circuitry. The advantages of zebrafish models stem in the high fecundity, fast development and transparency of the embryo. Disadvantages of both models originate in behavioral repertoires not allowing specific symptoms to be modeled, even when the models are combined. Especially modeling the verbal component of certain positive, negative and cognitive symptoms is currently impossible.

Psychosocial Stress Induces Schizophrenia-Like Behavior in Mice With Reduced MMP-9 Activity

Understanding gene-environment interactions in the pathogenesis of schizophrenia remains a major research challenge. Matrix metalloproteinase-9 (MMP-9) has been previously implicated in the pathophysiology of schizophrenia. In the present study, adolescent Mmp-9 heterozygous mice, with a genetically lower level of MMP-9, were subjected to resident-intruder psychosocial stress for 3 weeks and then examined in behavioral tests that evaluated cognitive deficits and positive- and negative-like symptoms of schizophrenia. Cognitive and positive symptoms in unstressed Mmp-9 heterozygous mice were unaffected by stress exposure, whereas negative symptoms were manifested only after stress exposure. Interestingly, negative symptoms were ameliorated by treatment with the antipsychotic drug clozapine. We describe a novel gene × environment interaction mouse model of schizophrenia. Lower MMP-9 levels in the brain might be a risk factor for schizophrenia that, in combination with environmental factors (e.g., psychosocial stress), may evoke schizophrenia-like symptoms that are sensitive to antipsychotic treatment.

Pregnancy exposure to carbon black nanoparticles exacerbates bleomycin-induced lung fibrosis in offspring via disrupting LKB1-AMPK-ULK1 axis-mediated autophagy

Accumulating evidence shows that carbon black nanoparticles (CBNPs) (one of the most used nanoparticles) can induce toxicity via induction of inflammation, oxidative stress and genotoxicity in vitro and in vivo, and epidemiological studies have indicated that the possible correlation between maternal immune activation and risk of developing neuropsychiatric disorder in the offspring. However, whether pregnancy exposure of CBNPs (Pr-CBNPs) enhances the susceptibility to bleomycin (BLM)-induced lung fibrosis in offspring is unknown. Herein, we demonstrated that Pr-CBNPs during gestational day 9-18 via intranasal administration could confer enhanced susceptibility to BLM-induced fibrotic response in offspring, including deteriorative lung pathologic changes and more collagen deposition. Intriguingly, we found that Pr-CBNPs repressed the activation of autophagy (an anti-fibrotic mechanism), which was moderately activated in offspring from mock group. Moreover, Pr-CBNPs was likely to disrupt the LKB1-AMPK-ULK1 axis (a key regulatory pathway for autophagy induction). In summary, this study provides the first evidence that pregnancy exposure to CBNPs can exacerbate BLM-induced lung fibrotic response in offspring probably through disruption of LKB1-AMPK-ULK1 axis-mediated autophagy.

Adolescent Δ9-Tetrahydrocannabinol Exposure and Astrocyte-Specific Genetic Vulnerability Converge on Nuclear Factor-κB-Cyclooxygenase-2 Signaling to Impair Memory in Adulthood

BACKGROUND

Although several studies have linked adolescent cannabis use to long-term cognitive dysfunction, there are negative reports as well. The fact that not all users develop cognitive impairment suggests a genetic vulnerability to adverse effects of cannabis, which are attributed to action of Δ9-tetrahydrocannabinol (Δ⁹-THC), a cannabis constituent and partial agonist of brain cannabinoid receptor 1. As both neurons and glial cells express cannabinoid receptor 1, genetic vulnerability could influence Δ⁹-THC-induced signaling in a cell type-specific manner.

METHODS

Here we use an animal model of inducible expression of dominant-negative disrupted in schizophrenia 1 (DN-DISC1) selectively in astrocytes to evaluate the molecular mechanisms, whereby an astrocyte genetic vulnerability could interact with adolescent Δ⁹-THC exposure to impair recognition memory in adulthood.

RESULTS

Selective expression of DN-DISC1 in astrocytes and adolescent treatment with Δ⁹-THC synergistically affected recognition memory in adult mice. Similar deficits in recognition memory were observed following knockdown of endogenous Disc1 in hippocampal astrocytes in mice treated with Δ⁹-THC during adolescence. At the molecular level, DN-DISC1 and Δ⁹-THC synergistically activated the nuclear factor-κB-cyclooxygenase-2 pathway in astrocytes and decreased immunoreactivity of parvalbumin-positive presynaptic inhibitory boutons around pyramidal neurons of the hippocampal CA3 area. The cognitive abnormalities were prevented in DN-DISC1 mice exposed to Δ⁹-THC by simultaneous adolescent treatment with the cyclooxygenase-2 inhibitor, NS398.

CONCLUSIONS

Our data demonstrate that individual vulnerability to cannabis can be exclusively mediated by astrocytes. Results of this work suggest that genetic predisposition within astrocytes can exaggerate Δ⁹-THC-produced cognitive impairments via convergent inflammatory signaling, suggesting possible targets for preventing adverse effects of cannabis within susceptible individuals.

Child maltreatment and psychosis

This paper reviews the literature on the association between experiences of child abuse and neglect and the development of psychoses. It then explores the premise that psychotic patients with a history of maltreatment may comprise a clinically and biological distinct subgroup. The review demonstrates that there is a growing consensus in the field that experiences of child maltreatment contribute to the onset of psychotic symptoms and psychotic disorders. There is also strong support for the premise that patients with psychotic disorders and histories of child maltreatment have distinct clinical characteristics and unique treatment needs, and emerging preliminary data to suggest psychotic patients with a history of maltreatment may comprise a distinct neurobiological subgroup. The mechanisms by which experiences of child maltreatment confers risk for psychotic disorders remains unknown, and the review highlights the value of incorporating translational research perspectives to advance knowledge in this area.

Sex and gender differences in schizophrenic psychoses-a critical review

Many sex and gender differences in schizophrenic psychoses have been reported, but few have been soundly replicated. A stable finding is the later age of onset in women compared to men. Gender differences in symptomatology, comorbidity, and neurocognition seem to reflect findings in the general population. There is increasing evidence for estrogens being psychoprotective in women and for hypothalamic-pituitary-gonadal dysfunction in both sexes.More methodologically sound, longitudinal, multi-domain, interdisciplinary research investigating both sex (biological) and gender (psychosocial) factors is required to better understand the different pathogenesis and etiologies of schizophrenic psychoses in women and men, thereby leading to better tailored treatments and improved outcomes.

Continuous performance test impairment in a 22q11.2 microdeletion mouse model: improvement by amphetamine

The 22q11.2 deletion syndrome (22q11.2DS) confers high risk of neurodevelopmental disorders such as schizophrenia and attention-deficit hyperactivity disorder. These disorders are associated with attentional impairment, the remediation of which is important for successful therapeutic intervention. We assessed a 22q11.2DS mouse model (Df(h22q11)/+) on a touchscreen rodent continuous performance test (rCPT) of attention and executive function that is analogous to human CPT procedures. Relative to wild-type littermates, Df(h22q11)/+ male mice showed impaired attentional performance as shown by decreased correct response ratio (hit rate) and a reduced ability to discriminate target stimuli from non-target stimuli (discrimination sensitivity, or d'). The Df(h22q11)/+ model exhibited decreased prefrontal cortical-hippocampal oscillatory synchrony within multiple frequency ranges during quiet wakefulness, which may represent a biomarker of cognitive dysfunction. The stimulant amphetamine (0-1.0 mg/kg, i.p.) dose-dependently improved d' in Df(h22q11)/+ mice whereas the highest dose of modafinil (40 mg/kg, i.p.) exacerbated their d' impairment. This is the first report to directly implicate attentional impairment in a 22q11.2DS mouse model, mirroring a key endophenotype of the human disorder. The capacity of the rCPT to detect performance impairments in the 22q11.2DS mouse model, and improvement following psychostimulant-treatment, highlights the utility and translational potential of the Df(h22q11)/+ model and this automated behavioral procedure.

Maternal Immune Activation and Neuropsychiatric Illness: A Translational Research Perspective

Epidemiologic studies, including prospective birth cohort investigations, have implicated maternal immune activation in the etiology of neuropsychiatric disorders. Maternal infectious pathogens and inflammation are plausible risk factors for these outcomes and have been associated with schizophrenia, autism spectrum disorder, and bipolar disorder. Concurrent with epidemiologic research are animal models of prenatal immune activation, which have documented behavioral, neurochemical, neuroanatomic, and neurophysiologic disruptions that mirror phenotypes observed in these neuropsychiatric disorders. Epidemiologic studies of maternal immune activation offer the advantage of directly evaluating human populations but are limited in their ability to uncover pathogenic mechanisms. Animal models, on the other hand, are limited in their generalizability to psychiatric disorders but have made significant strides toward discovering causal relationships and biological pathways between maternal immune activation and neuropsychiatric phenotypes. Incorporating these risk factors in reverse translational animal models of maternal immune activation has yielded a wealth of data supporting the predictive potential of epidemiologic studies. To further enhance the translatability between epidemiology and basic science, the authors propose a complementary approach that includes deconstructing neuropsychiatric outcomes of maternal immune activation into key pathophysiologically defined phenotypes that are identifiable in humans and animals and that evaluate the interspecies concordance regarding interactions between maternal immune activation and genetic and epigenetic factors, including processes involving intergenerational disease transmission. [AJP AT 175: Remembering Our Past As We Envision Our Future October 1857: The Pathology of Insanity J.C. Bucknill: "In the brain the state of inflammation itself either very quickly ceases or very soon causes death; but when it does cease it leaves behind it consequences which are frequently the causes of insanity, and the conditions of cerebral atrophy." (Am J Psychiatry 1857; 14:172-193 )].

Transcriptomic analysis reveals oxidative phosphorylation activation in an adolescent social isolation rat model

Complex interactions between genetic and environmental factors exert a sustained influence on the pathogenesis of schizophrenia (SCZ). Adolescent social isolation is regarded as a typical paradigm for SCZ. However, the underlying pathological mechanisms are not fully understood. In this study, adolescent Sprague-Dawley (SD) rats were placed in isolation rearing (IR) or social rearing (SR) conditions from postnatal day (PND) 21 to 34 to establish a SCZ disease model and a control model, respectively. Prepulse inhibition (PPI) assays and elevated plus maze tests were performed on PND 56. Next, prefrontal cortex (PFC) tissues were isolated for transcriptomic sequencing and RT-qPCR analyses. The results indicated that adolescent social isolation induced anxious behaviors and disrupted PPIs as well as specific PFC gene expression patterns in adult SD rats. A total of 196 genes were identified as upregulated, and 748 genes were identified as down-regulated in the IR group compared with those in the SR group. Differentially expressed genes (DEGs) were highly enriched in the KEGG pathways associated with the comorbidity of neurological disorder and oxidative phosphorylation (OXPHOS); 26 out of 27 comorbid neurological disorder-associated DEGs overlapped with 31 OXPHOS-associated DEGs. Those 26 overlapping DEGs were all upregulated in the IR group and could easily distinguish the IR group from the SR group; 6 of these DEGs (COX7C, NDUFB11, NDUFA2, NDUFC2, ATP5C1, and COX6A1) were verified by RT-qPCR. Here, we provide a systematic overview of gene expression alterations in adolescent-social-isolation-induced SCZ (ASI-SCZ), which suggests that genes that are associated with the comorbidity of neurological disorders, especially OXPHOS-related genes, contribute to the pathogenesis of ASI-SCZ.

Sensorimotor gating deficits in "two-hit" models of schizophrenia risk factors

Genetic and environmental models of neuropsychiatric disease have grown exponentially over the last 20years. One measure that is often used to evaluate the translational relevance of these models to human neuropsychiatric disease is prepulse inhibition of startle (PPI), an operational measure of sensorimotor gating. Deficient PPI characterizes several neuropsychiatric disorders but has been most extensively studied in schizophrenia. It has become a useful tool in translational neuropharmacological and molecular genetics studies because it can be measured across species using almost the same experimental parameters. Although initial studies of PPI in rodents were pharmacological because of the robust predictive validity of PPI for antipsychotic efficacy, more recently, PPI has become standard common behavioral measures used in genetic and neurodevelopmental models of schizophrenia. Here we review "two hit" models of schizophrenia and discuss the utility of PPI as a tool in phenotyping these models of relevant risk factors. In the review, we consider approaches to rodent models of genetic and neurodevelopmental risk factors and selectively review "two hit" models of gene×environment and environment×environment interactions in which PPI has been measured.

Schizophrenia-related dysbindin-1 gene is required for innate immune response and homeostasis in the developing subventricular zone

Schizophrenia is a neurodevelopmental disorder likely caused by environmental and genetic risk factors but functional interactions between the risk factors are unclear. We tested the hypothesis that dysbindin-1 (Dtnbp1) gene mutation combined with postnatal exposure to viral mimetic polyI:C results in schizophrenia-related behavioural changes in adulthood, and mediates polyI:C-induced inflammation in the subventricular zone (SVZ). Adult Sandy (Sdy, Dtnbp1 mutant) mice given early postnatal polyI:C injections displayed reduced prepulse inhibition of startle, reduced locomotion and deficits in novel object recognition. PolyI:C induced a canonical immune response in the SVZ; it increased mRNA expression of its toll-like receptor 3 (Tlr3) and downstream transcription factors RelA and Sp1. PolyI:C also increased SVZ Dtnbp1 mRNA expression, suggesting dysbindin-1 regulates immune responses. Dysbindin-1 loss in Sdy mice blocked the polyI:C-induced increases in mRNA expression of Tlr3, RelA and Sp1 in the SVZ. Dtnbp1 overexpression in SVZ-derived Sdy neurospheres rescued Tlr3, RelA and Sp1 mRNA expression supporting a functional interaction between dysbindin-1 and polyI:C-induced inflammation. Immunohistochemistry showed higher Iba1+ immune cell density in the SVZ of Sdy mice than in WT postnatally. PolyI:C did not alter SVZ Iba1+ cell density but increased CD45+/Iba1− cell numbers in the SVZ of Sdy mice. Finally, polyI:C injections in Sdy, but not WT mice reduced postnatal and adult SVZ proliferation. Together, we show novel functional interactions between the schizophrenia-relevant dysbindin-1 gene and the immune response to polyI:C. This work sheds light on the molecular basis for amplified abnormalities due to combined genetic predisposition and exposure to environmental schizophrenia risk factors.

Interactions Between Variation in Candidate Genes and Environmental Factors in the Etiology of Schizophrenia and Bipolar Disorder: a Systematic Review

Schizophrenia and bipolar disorder (BD) are complex and multidimensional disorders with high heritability rates. The contribution of genetic factors to the etiology of these disorders is increasingly being recognized as the action of multiple risk variants with small effect sizes, which might explain only a minor part of susceptibility. On the other site, numerous environmental factors have been found to play an important role in their causality. Therefore, in recent years, several studies focused on gene × environment interactions that are believed to bridge the gap between genetic underpinnings and environmental insults. In this article, we performed a systematic review of studies investigating gene × environment interactions in BD and schizophrenia spectrum phenotypes. In the majority of studies from this field, interacting effects of variation in genes encoding catechol-O-methyltransferase (COMT), brain-derived neurotrophic factor (BDNF), and FK506-binding protein 5 (FKBP5) have been explored. Almost consistently, these studies revealed that polymorphisms in COMT, BDNF, and FKBP5 genes might interact with early life stress and cannabis abuse or dependence, influencing various outcomes of schizophrenia spectrum disorders and BD. Other interactions still require further replication in larger clinical and non-clinical samples. In addition, future studies should address the direction of causality and potential mechanisms of the relationship between gene × environment interactions and various categories of outcomes in schizophrenia and BD.

Maternal immune activation induced by lipopolysaccharide triggers immune response in pregnant mother and fetus, and induces behavioral impairment in adult rats

Evidence suggest that prenatal immune system disturbance contributes largely to the pathophysiology of neuropsychiatric disorders. We investigated if maternal immune activation (MIA) could induce inflammatory alterations in fetal brain and pregnant rats. Adult rats subjected to MIA also were investigated to evaluate if ketamine potentiates the effects of infection. On gestational day 15, Wistar pregnant rats received lipopolysaccharide (LPS) to induce MIA. After 6, 12 and 24 h, fetus brain, placenta, and amniotic fluid were collected to evaluate early effects of LPS. MIA increased oxidative stress and expression of metalloproteinase in the amniotic fluid and fetal brain. The blood brain barrier (BBB) integrity in the hippocampus and cortex as well integrity of placental barrier (PB) in the placenta and fetus brain were dysregulated after LPS induction. We observed elevated pro- and anti-inflammatory cytokines after LPS in fetal brain. Other group of rats from postnatal day (PND) 54 after LPS received injection of ketamine at the doses of 5, 15, and 25 mg/kg. On PND 60 rats were subjected to the memories tests, spontaneous locomotor activity, and pre-pulse inhibition test (PPI). Rats that receive MIA plus ketamine had memory impairment and a deficit in the PPI. Neurotrophins were increased in the hippocampus and reduced in the prefrontal cortex in the LPS plus ketamine group. MIA induced oxidative stress and inflammatory changes that could be, at least in part, related to the dysfunction in the BBB and PB permeability of pregnant rats and offspring. Besides, this also generates behavioral deficits in the rat adulthood's that are potentiated by ketamine.

An Update on Promising Biomarkers in Schizophrenia

Given the heterogeneity of symptoms in patients with schizophrenia and current treatment limitations, biomarkers may play an important role in diagnosis, subtype stratification, and the assessment of treatment response. Though many potential biomarkers have been studied, we have chosen to focus on some of the most promising and potentially clinically relevant biomarkers to review herein. These include markers of inflammation, neuroimaging biomarkers, brain-derived neurotrophic factor, genetic/epigenetic markers, and speech analysis. This will provide a broad overview of putative biomarkers that could become clinically relevant in the future, though none currently appear ready to assist the clinician in identifying cases of schizophrenia, subtypes of the disorder, treatment choice, or response. Nonetheless, some biomarkers, such as C-reactive protein (CRP), may be useful at identifying individuals who may be more highly inflamed, which could drive treatment choice. Though checking CRP is not a standard of practice, this is one example of how biomarkers may drive treatment decisions in the future, supporting precision medicine. Similarly, technological advances may one day allow clinicians to detect changes in speech patterns, which could represent a noninvasive, clinically useful tool in the future. We conclude the review by highlighting two important potential clinical uses for biomarkers in schizophrenia: the identification of individuals who may convert from clinical high risk and the stratification of patients via different biomarkers that may supersede clinical diagnosis. Given the enormous burden of illness of schizophrenia, the search for clinically relevant biomarkers is of great importance to improve the lives of patients with the disorder.

Effects of genetic and environmental risk for schizophrenia on hippocampal activity and psychosis-like behavior in mice

Schizophrenia is a serious mental illness most notably characterized by psychotic symptoms. In humans, psychotic disorders are associated with specific hippocampal pathology. However, animal model systems for psychosis often lack this pathology, and have been weak in providing a representation of psychosis. We utilized a double-risk model system combining genetic risk with environmental stress. We hypothesized these factors will induce hippocampal subfield pathology consistent with human findings, as well as behavioral phenotypes relevant to psychosis. To address this, we exposed wild-type and transgenic Disc1 dominant negative (Disc1-deficient) mice to maternal deprivation. In adulthood, hippocampal subfields were examined for signs of cellular and behavioral pathology associated with psychosis. Mice exposed to maternal deprivation showed a decrease in dentate gyrus activity, and an increase in CA3/CA1 activity. Furthermore, results demonstrated a differential behavioral effect between maternal deprivation and Disc1 deficiency, with maternal deprivation associated with a hyperactive phenotype and impaired prepulse inhibition, and Disc1 deficiency causing an impairment in fear conditioning. These results suggest distinct consequences of environmental and genetic risk factors contributing to psychosis, with maternal deprivation inducing a state more wholly consistent with schizophrenia psychosis. Further research is needed to determine if this pathology is causally related to a specific behavioral phenotype. The development of a strong inference animal model system for psychosis would satisfy a high medical need in schizophrenia research.

Deconstructing Schizophrenia: Advances in Preclinical Models for Biomarker Identification

Schizophrenia is considered to develop as a consequence of genetic and environmental factors impacting on brain neural systems and circuits during vulnerable neurodevelopmental periods, thereby resulting in symptoms in early adulthood. Understanding of the impact of schizophrenia risk factors on brain biology and behaviour can help in identifying biologically relevant pathways that are attractive for informing clinical studies and biomarker development. In this chapter, we emphasize the importance of adopting a reciprocal forward and reverse translation approach that is iteratively updated when additional new information is gained, either preclinically or clinically, for offering the greatest opportunity for discovering panels of biomarkers for the diagnosis, prognosis and treatment of schizophrenia. Importantly, biomarkers for identifying those at risk may inform early intervention strategies prior to the development of schizophrenia.Given the emerging nature of this approach in the field, this review will highlight recent research of preclinical biomarkers in schizophrenia that show the most promise for informing clinical needs with an emphasis on relevant imaging, electrophysiological, cognitive behavioural and biochemical modalities. The implementation of this reciprocal translational approach is exemplified firstly by the production and characterization of preclinical models based on the glutamate hypofunction hypothesis, genetic and environmental risk factors for schizophrenia (reverse translation), and then the recent clinical recognition of the thalamic reticular thalamus (TRN) as an important locus of brain dysfunction in schizophrenia as informed by preclinical findings (forward translation).

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.

Genetic Approaches to Understanding Psychiatric Disease

Human genetic studies have been the driving force in bringing to light the underlying biology of psychiatric conditions. As these studies fill in the gaps in our knowledge of the mechanisms at play, we will be better equipped to design therapies in rational and targeted ways, or repurpose existing therapies in previously unanticipated ways. This review is intended for those unfamiliar with psychiatric genetics as a field and provides a primer on different modes of genetic variation, the technologies currently used to probe them, and concepts that provide context for interpreting the gene-phenotype relationship. Like other subfields in human genetics, psychiatric genetics is moving from microarray technology to sequencing-based approaches as barriers of cost and expertise are removed, and the ramifications of this transition are discussed here. A summary is then given of recent genetic discoveries in a number of neuropsychiatric conditions, with particular emphasis on neurodevelopmental conditions. The general impact of genetics on drug development has been to underscore the extensive etiological heterogeneity in seemingly cohesive diagnostic categories. Consequently, the path forward is not in therapies hoping to reach large swaths of patients sharing a clinically defined diagnosis, but rather in targeting patients belonging to specific "biotypes" defined through a combination of objective, quantifiable data, including genotype.

Two-hit model of schizophrenia induced by neonatal immune activation and peripubertal stress in rats: Study of sex differences and brain oxidative alterations

Schizophrenia is considered to be a developmental disorder with distinctive sex differences. Aiming to simulate the vulnerability of the third trimester of human pregnancy to the developmental course of schizophrenia, an animal model was developed, using neonatal poly(I:C) as a first-hit, and peripubertal stress as a second-hit, i.e. a two-hit model. Since, to date, there have been no references to sex differences in the two-hit model, our study sought to determine sex influences on the development of behavior and brain oxidative change in adult rats submitted to neonatal exposure to poly(I:C) on postnatal days 5-7 as well as peripubertal unpredictable stress (PUS). Our results showed that adult two-hit rats present sex-specific behavioral alterations, with females showing more pronounced deficits in prepulse inhibition of the startle reflex and hyperlocomotion, while males showing more deficits in social interaction. Male and female animals exhibited similar working memory deficits. The levels of the endogenous antioxidant, reduced glutathione, were decreased in the prefrontal cortex (PFC) of both male and female animals exposed to both poly(I:C) and poly(I:C)+PUS. Only females presented decrements in GSH levels in the striatum. Nitrite levels were increased in the PFC of male and in the striatum of female poly(I:C)+PUS rats. Increased lipid peroxidation was observed in the PFC of females and in the striatum of males and females exposed to poly(I:C) and poly(I:C)+PUS. Thus, the present study presents evidence for sex differences in behavior and oxidative brain change induced by a two-hit model of schizophrenia.