Prenatal lipopolysaccharide treatment enhances MK-801-induced psychotomimetic effects in rats

Insights into the Potential Impact of Quetiapine on the Microglial Trajectory and Inflammatory Response in Organotypic Cortical Cultures Derived from Rat Offspring

Atypical antipsychotics currently constitute the first-line medication for schizophrenia, with quetiapine being one of the most commonly prescribed representatives of the group. Along with its specific affinity for multiple receptors, this compound exerts other biological characteristics, among which anti-inflammatory effects are strongly suggested. Simultaneously, published data indicated that inflammation and microglial activation could be diminished by stimulation of the CD200 receptor (CD200R), which takes place by binding to its ligand (CD200) or soluble CD200 fusion protein (CD200Fc). Therefore, in the present study, we sought to evaluate whether quetiapine could affect certain aspects of microglial activity, including the CD200-CD200R and CX3CL1-CX3CR1 axes, which are involved in the regulation of neuron-microglia interactions, as well as the expression of selected markers of the pro- and anti-inflammatory profile of microglia (Cd40, Il-1β, Il-6, Cebpb, Cd206, Arg1, Il-10 and Tgf-β). Concurrently, we examined the impact of quetiapine and CD200Fc on the IL-6 and IL-10 protein levels. The abovementioned aspects were investigated in organotypic cortical cultures (OCCs) prepared from the offspring of control rats (control OCCs) or those subjected to maternal immune activation (MIA OCCs), which is a widely implemented approach to explore schizophrenia-like disturbances in animals. The experiments were performed under basal conditions and after additional exposure to the bacterial endotoxin lipopolysaccharide (LPS), according to the "two-hit" hypothesis of schizophrenia. The results of our research revealed differences between control and MIA OCCs under basal conditions and in response to treatment with LPS in terms of lactate dehydrogenase and nitric oxide release as well as Cd200r, Il-1β, Il-6 and Cd206 expression. The additional stimulation with the bacterial endotoxin resulted in a notable change in the mRNA levels of pro- and anti-inflammatory microglial markers in both types of OCCs. Quetiapine diminished the influence of LPS on Il-1β, Il-6, Cebpb and Arg1 expression in control OCCs as well as on IL-6 and IL-10 levels in MIA OCCs. Moreover, CD200Fc reduced the impact of the bacterial endotoxin on IL-6 production in MIA OCCs. Thus, our results demonstrated that quetiapine, as well as the stimulation of CD200R by CD200Fc, beneficially affected LPS-induced neuroimmunological changes, including microglia-related activation.

Quetiapine Ameliorates MIA-Induced Impairment of Sensorimotor Gating: Focus on Neuron-Microglia Communication and the Inflammatory Response in the Frontal Cortex of Adult Offspring of Wistar Rats

The maternal immune activation produced by the systemic administration of lipopolysaccharide (LPS) in rats provides valuable insights into the basis of behavioural schizophrenia-like disturbances and biochemical changes in the brains of the offspring, such as microglial activation. Regarding therapy, antipsychotics continually constitute the cornerstone of schizophrenia treatment. To their various efficacy and side effects, as well as not fully recognised mechanisms of action, further characteristics have been suggested, including an anti-inflammatory action via the impact on neuron–microglia axes responsible for inhibition of microglial activation. Therefore, in the present study, we sought to determine whether chronic treatment with chlorpromazine, quetiapine or aripiprazole could influence schizophrenia-like behavioural disturbances at the level of sensorimotor gating in male offspring prenatally exposed to LPS. Simultaneously, we wanted to explore if the chosen antipsychotics display a positive impact on the neuroimmunological parameters in the brains of these adult animals with a special focus on the ligand-receptor axes controlling neuron–microglia communication as well as pro- and anti-inflammatory factors related to the microglial activity. The results of our research revealed the beneficial effect of quetiapine on deficits in sensorimotor gating observed in prenatally LPS-exposed offspring. In terms of axes controlling neuron–microglia communication and markers of microglial reactivity, we observed a subtle impact of quetiapine on hippocampal Cx3cl1 and Cx3cr1 levels, as well as cortical Cd68 expression. Hence, further research is required to fully define and explain the involvement of quetiapine and other antipsychotics in Cx3cl1-Cx3cr1 and/or Cd200-Cd200r axes modulation and inflammatory processes in the LPS-based model of schizophrenia-like disturbances.

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.

Behavioral Alterations and Decreased Number of Parvalbumin-Positive Interneurons in Wistar Rats after Maternal Immune Activation by Lipopolysaccharide: Sex Matters

Maternal immune activation (MIA) during pregnancy represents an important environmental factor in the etiology of schizophrenia and autism spectrum disorders (ASD). Our goal was to investigate the impacts of MIA on the brain and behavior of adolescent and adult offspring, as a rat model of these neurodevelopmental disorders. We injected bacterial lipopolysaccharide (LPS, 1 mg/kg) to pregnant Wistar dams from gestational day 7, every other day, up to delivery. Behavior of the offspring was examined in a comprehensive battery of tasks at postnatal days P45 and P90. Several brain parameters were analyzed at P28. The results showed that prenatal immune activation caused social and communication impairments in the adult offspring of both sexes; males were affected already in adolescence. MIA also caused prepulse inhibition deficit in females and increased the startle reaction in males. Anxiety and hypolocomotion were apparent in LPS-affected males and females. In the 28-day-old LPS offspring, we found enlargement of the brain and decreased numbers of parvalbumin-positive interneurons in the frontal cortex in both sexes. To conclude, our data indicate that sex of the offspring plays a crucial role in the development of the MIA-induced behavioral alterations, whereas changes in the brain apparent in young animals are sex-independent.

Role of Polyinosinic:Polycytidylic Acid-Induced Maternal Immune Activation and Subsequent Immune Challenge in the Behaviour and Microglial Cell Trajectory in Adult Offspring: A Study of the Neurodevelopmental Model of Schizophrenia

Multiple lines of evidence support the pathogenic role of maternal immune activation (MIA) in the occurrence of the schizophrenia-like disturbances in offspring. While in the brain the homeostatic role of neuron-microglia protein systems is well documented, the participation of the CX3CL1-CX3CR1 and CD200-CD200R dyads in the adverse impact of MIA often goes under-recognized. Therefore, in the present study, we examined the effect of MIA induced by polyinosinic:polycytidylic acid (Poly I:C) on the CX3CL1-CX3CR1 and CD200-CD200R axes, microglial trajectory (MhcII, Cd40, iNos, Il-1β, Tnf-α, Il-6, Arg1, Igf-1, Tgf-β and Il-4), and schizophrenia-like behaviour in adult male offspring of Sprague-Dawley rats. Additionally, according to the “two-hit” hypothesis of schizophrenia, we evaluated the influence of acute challenge with Poly I:C in adult prenatally MIA-exposed animals on the above parameters. In the present study, MIA evoked by Poly I:C injection in the late period of gestation led to the appearance of schizophrenia-like disturbances in adult offspring. Our results revealed the deficits manifested as a diminished number of aggressive interactions, presence of depressive-like episodes, and increase of exploratory activity, as well as a dichotomy in the sensorimotor gating in the prepulse inhibition (PPI) test expressed as two behavioural phenotypes (MIA_PPI-low and MIA_PPI-high). Furthermore, in the offspring rats subjected to a prenatal challenge (i.e., MIA) we noticed the lack of modulation of behavioural changes after the additional acute immune stimulus (Poly I:C) in adulthood. The important finding reported in this article is that MIA affects the expression and levels of the neuron-microglia proteins in the frontal cortex and hippocampus of adult offspring. We found that the changes in the CX3CL1-CX3CR1 axis could affect microglial trajectory, including decreased hippocampal mRNA level of MhcII and elevated cortical expression of Igf-1 in the MIA_PPI-high animals and/or could cause the up-regulation of an inflammatory response (Il-6, Tnf-α, iNos) after the “second hit” in both examined brain regions and, at least in part, might differentiate behavioural disturbances in adult offspring. Consequently, the future effort to identify the biological background of these interactions in the Poly I:C-induced MIA model in Sprague-Dawley rats is desirable to unequivocally clarify this issue.

The prenatal challenge with lipopolysaccharide and polyinosinic:polycytidylic acid disrupts CX3CL1-CX3CR1 and CD200-CD200R signalling in the brains of male rat offspring: a link to schizophrenia-like behaviours

BACKGROUND

The bidirectional communication between neurons and microglia is fundamental for the homeostasis and biological function of the central nervous system. Maternal immune activation (MIA) is considered to be one of the factors affecting these interactions. Accordingly, MIA has been suggested to be involved in several neuropsychiatric diseases, including schizophrenia. The crucial regulatory systems for neuron-microglia crosstalk are the CX3CL1-CX3CR1 and CD200-CD200R axes.

METHODS

We aimed to clarify the impact of MIA on CX3CL1-CX3CR1 and CD200-CD200R signalling pathways in the brains of male Wistar rats in early and adult life by employing two neurodevelopmental models of schizophrenia based on the prenatal challenge with lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (Poly I:C). We also examined the effect of MIA on the expression of microglial markers and the profile of cytokines released in the brains of young offspring, as well as the behaviour of adult animals. Moreover, we visualized the localization of ligand-receptor systems in the hippocampal regions (CA1, CA3 and DG) and the frontal cortex of young rats exposed to MIA. The differences between groups were analysed using Student's t test.

RESULTS

We observed that MIA altered developmental trajectories in neuron-microglia communication in the brains of young offspring, as evidenced by the disruption of CX3CL1-CX3CR1 and/or CD200-CD200R axes. Our data demonstrated the presence of abnormalities after LPS-induced MIA in levels of Cd40, Il-1β, Tnf-α, Arg1, Tgf-β and Il-10, as well as IBA1, IL-1β and IL-4, while after Poly I:C-generated MIA in levels of Cd40, iNos, Il-6, Tgf-β, Il-10, and IBA1, IL-1β, TNF-α, IL-6, TGF-β and IL-4 early in the life of male animals. In adult male rats that experienced prenatal exposure to MIA, we observed behavioural changes resembling a schizophrenia-like phenotype.

CONCLUSIONS

Our study provides evidence that altered CX3CL1-CX3CR1 and/or CD200-CD200R pathways, emerging after prenatal immune challenge with LPS and Poly I:C, might be involved in the aetiology of schizophrenia.

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

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

Studies on Haloperidol and Adjunctive α-Mangostin or Raw Garcinia mangostana Linn Pericarp on Bio-Behavioral Markers in an Immune-Inflammatory Model of Schizophrenia in Male Rats

Schizophrenia is a severe brain disorder that is associated with neurodevelopmental insults, such as prenatal inflammation, that introduce redox-immune-inflammatory alterations and risk for psychotic symptoms later in life. Nutraceuticals may offer useful adjunctive benefits. The aim of this study was to examine the therapeutic effects of Garcinia mangostana Linn (GML) and one of its active constituents, α-mangostin (AM), alone and as adjunctive treatment with haloperidol (HAL) on schizophrenia related bio-behavioral alterations in a maternal immune-activation (MIA) model. Sprague-Dawley dams were exposed to lipopolysaccharide (LPS) (n = 18) or vehicle (n = 3) on gestational days 15 and 16. Male offspring (n = 72) were treated from PND 52-66 with either vehicle, HAL (2 mg/kg), GML (50 mg/kg), HAL + GML, AM (20 mg/kg), or HAL + AM. Control dams and control offspring were treated with vehicle. In order to cover the mood-psychosis continuum, prepulse inhibition (PPI) of startle, open field test (locomotor activity), and the forced swim test (depressive-like behavior) were assessed on PND's 64-65, followed by assay of frontal-cortical lipid peroxidation and plasma pro-inflammatory cytokines, viz. interleukin-1 (IL-1) and tumor necrosis factor-α (TNF-α). MIA-induced deficits in sensorimotor gating were reversed by HAL and HAL + GML, but not GML and AM alone. MIA-induced depressive-like behavior was reversed by AM and GML alone and both in combination with HAL, with the combinations more effective than HAL. MIA-induced cortical lipid peroxidation was reversed by HAL and AM, with elevated IL-6 levels restored by GML, AM, HAL, and HAL + GML. Elevated TNF-α was only reversed by GML and HAL + GML. Concluding, prenatal LPS-induced psychotic- and depressive-like bio-behavioral alterations in offspring are variably responsive to HAL, GML, and AM, with depressive (but not psychosis-like) manifestations responding to GML, AM, and combinations with HAL. AM may be a more effective antioxidant than GML in vivo, although this does not imply an improved therapeutic response, for which trials are required.

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

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

Neonatal immune activation by lipopolysaccharide causes inadequate emotional responses to novel situations but no changes in anxiety or cognitive behavior in Wistar rats

Infection during the prenatal or neonatal stages of life is considered one of the major risk factors for the development of mental diseases such as schizophrenia or autism. However, the impacts of such an immune challenge on adult behavior are still not clear. In our study, we used a model of early postnatal immune activation by the application of bacterial endotoxin lipopolysaccharide (LPS) to rat pups at a dose of 2 mg/kg from postnatal day (PD) 5 to PD 9. In adulthood, the rats were tested in a battery of tasks probing various aspects of behavior: spontaneous activity (open field test), social behavior (social interactions and female bedding exploration), anxiety (elevated plus maze), cognition (active place avoidance in Carousel) and emotional response (ultrasonic vocalization recording). Moreover, we tested sensitivity to acute challenge with MK-801, a psychotomimetic drug. Our results show that the application of LPS led to increased self-grooming in the female bedding exploration test and inadequate emotional reactions in Carousel maze displayed by ultrasonic vocalizations. However, it did not have serious consequences on exploration, locomotion, social behavior or cognition. Furthermore, exposition to MK-801 did not trigger social or cognitive deficits in the LPS-treated rats. We conclude that the emotional domain is the most sensitive to the changes induced by neonatal immune activation in rats, including a disrupted response to novel and stressful situations in early adulthood (similar to that observed in human patients suffering from schizophrenia or autism), while other aspects of tested behavior remain unaffected.

N-acetyl cysteine reverses bio-behavioural changes induced by prenatal inflammation, adolescent methamphetamine exposure and combined challenges

RATIONALE

Schizophrenia is associated with prenatal inflammation and/or postnatal stressors such as drug abuse, resulting in immune-redox dysfunction. Antioxidants may offer therapeutic benefits.

OBJECTIVES

The objective of this study is to investigate N-acetyl cysteine (NAC) as a therapeutic antioxidant to reverse schizophrenia-like bio-behavioural changes in rats exposed to maternal immune activation (MIA), adolescent methamphetamine (MA) or a combination thereof.

METHODS

Sprague-Dawley offspring prenatally exposed to saline/lipopolysaccharide (LPS) received saline or MA (0.2-6 mg kg^-1 twice daily × 16 days) during adolescence and divided into LPS, MA and LPS + MA groups. Vehicle/NAC (150 mg kg^-1 × 14 days) was administered following MA/saline exposure on postnatal day 51-64. Social interaction, novel object recognition and prepulse inhibition (PPI) of startle, as well as regional brain monoamines, lipid peroxidation, plasma reactive oxygen species (ROS) and pro- and anti-inflammatory cytokines (TNF-α; IL-10), were assessed.

RESULTS

NAC reversed LPS, MA and LPS + MA-induced anxiety-like social withdrawal behaviours, as well as MA and LPS + MA-induced deficits in recognition memory. PPI deficits were evident in MA, LPS and LPS + MA models, with NAC reversing that following LPS + MA. NAC reversed LPS, MA and LPS + MA-induced frontal cortical dopamine (DA) and noradrenaline (NA) elevations, LPS and LPS + MA-induced frontal cortical 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT) and striatal NA deficits as well as LPS + MA-induced frontal cortical 5-HT turnover. Decreased IL-10 in the LPS, MA and LPS + MA animals, and increased TNF-α in the LPS and MA animals, was reversed with NAC. NAC also reversed elevated lipid peroxidation and ROS in the LPS and LPS + MA animals.

CONCLUSIONS

Prenatal LPS, LPS + postnatal MA challenge during adolescence, and to a lesser extent MA alone, promotes schizophrenia-like bio-behavioural changes later in life that are reversed by NAC, emphasizing therapeutic potential for schizophrenia and MA-associated psychosis. The nature and timing of the dual-hit are critical.

Neurodevelopmental Animal Models Reveal the Convergent Role of Neurotransmitter Systems, Inflammation, and Oxidative Stress as Biomarkers of Schizophrenia: Implications for Novel Drug Development

Schizophrenia is a life altering disease with a complex etiology and pathophysiology, and although antipsychotics are valuable in treating the disorder, certain symptoms and/or sufferers remain resistant to treatment. Our poor understanding of the underlying neuropathological mechanisms of schizophrenia hinders the discovery and development of improved pharmacological treatment, so that filling these gaps is of utmost importance for an improved outcome. A vast amount of clinical data has strongly implicated the role of inflammation and oxidative insults in the pathophysiology of schizophrenia. Preclinical studies using animal models are fundamental in our understanding of disease development and pathology as well as the discovery and development of novel treatment options. In particular, social isolation rearing (SIR) and pre- or postnatal inflammation (PPNI) have shown great promise in mimicking the biobehavioral manifestations of schizophrenia. Furthermore, the "dual-hit" hypothesis of schizophrenia states that a first adverse event such as genetic predisposition or a prenatal insult renders an individual susceptible to develop the disease, while a second insult (e.g., postnatal inflammation, environmental adversity, or drug abuse) may be necessary to precipitate the full-blown syndrome. Animal models that emphasize the "dual-hit" hypothesis therefore provide valuable insight into understanding disease progression. In this Review, we will discuss SIR, PPNI, as well as possible "dual-hit" animal models within the context of the redox-immune-inflammatory hypothesis of schizophrenia, correlating such changes with the recognized monoamine and behavioral alterations of schizophrenia. Finally, based on these models, we will review new therapeutic options, especially those targeting immune-inflammatory and redox pathways.

Prenatal stress is a vulnerability factor for altered morphology and biological activity of microglia cells

Several lines of evidence suggest that the dysregulation of the immune system is an important factor in the development of depression. Microglia are the resident macrophages of the central nervous system and a key player in innate immunity of the brain. We hypothesized that prenatal stress (an animal model of depression) as a priming factor could affect microglial cells and might lead to depressive-like disturbances in adult male rat offspring. We investigated the behavioral changes (sucrose preference test, Porsolt test), the expression of C1q and CD40 mRNA and the level of microglia (Iba1 positive) in 3-month-old control and prenatally stressed male offspring rats. In addition, we characterized the morphological and biochemical parameters of potentially harmful (NO, iNOS, IL-1β, IL-18, IL-6, TNF-α, CCL2, CXCL12, CCR2, CXCR4) and beneficial (insulin-like growth factor-1 (IGF-1), brain derived neurotrophic factor (BDNF)) phenotypes in cultures of microglia obtained from the cortices of 1–2 days old control and prenatally stressed pups. The adult prenatally stressed rats showed behavioral (anhedonic- and depression-like) disturbances, enhanced expression of microglial activation markers and an increased number of Iba1-immunopositive cells in the hippocampus and frontal cortex. The morphology of glia was altered in cultures from prenatally stressed rats, as demonstrated by immunofluorescence microscopy. Moreover, in these cultures, we observed enhanced expression of CD40 and MHC II and release of pro-inflammatory cytokines, including IL-1β, IL-18, TNF-α and IL-6. Prenatal stress significantly up-regulated levels of the chemokines CCL2, CXCL12 and altered expression of their receptors, CCR2 and CXCR4 while IGF-1 production was suppressed in cultures of microglia from prenatally stressed rats. Our results suggest that prenatal stress may lead to excessive microglia activation and contribute to the behavioral changes observed in depression in adulthood.

Prenatal LPS-exposure--a neurodevelopmental rat model of schizophrenia--differentially affects cognitive functions, myelination and parvalbumin expression in male and female offspring

Maternal infection during pregnancy increases the risk for the offspring to develop schizophrenia. Gender differences can be seen in various features of the illness and sex steroid hormones (e.g. estrogen) have strongly been implicated in the disease pathology. In the present study, we evaluated sex differences in the effects of prenatal exposure to a bacterial endotoxin (lipopolysaccharide, LPS) in rats. Pregnant dams received LPS-injections (100 μg/kg) at gestational day 15 and 16. The offspring was then tested for prepulse inhibition (PPI), locomotor activity, anxiety-like behavior and object recognition memory at various developmental time points. At postnatal day (PD) 33 and 60, prenatally LPS-exposed rats showed locomotor hyperactivity which was similar in male and female offspring. Moreover, prenatal LPS-treatment caused PPI deficits in pubertal (PD45) and adult (PD90) males while PPI impairments were found only at PD45 in prenatally LPS-treated females. Following prenatal LPS-administration, recognition memory for objects was impaired in both sexes with males being more severely affected. Additionally, we assessed prenatal infection-induced alterations of parvalbumin (Parv) expression and myelin fiber density. Male offspring born to LPS-challenged mothers showed decreased myelination in cortical and limbic brain regions as well as reduced numbers of Parv-expressing cells in the medial prefrontal cortex (mPFC), hippocampus and entorhinal cortex. In contrast, LPS-exposed female rats showed only a modest decrease in myelination and Parv immunoreactivity. Collectively, our data indicate that some of the prenatal immune activation effects are sex dependent and further strengthen the importance of taking into account gender differences in animal models of schizophrenia.

Different presence of Chlamydia pneumoniae, herpes simplex virus type 1, human herpes virus 6, and Toxoplasma gondii in schizophrenia: meta-analysis and analytical study

In the present study we have performed both a meta-analysis and an analytical study exploring the presence of Chlamydia pneumoniae, herpes simplex virus type 1, human herpes virus 6, and Toxoplasma gondii antibodies in a sample of 143 schizophrenic patients and 143 control subjects. The meta-analysis was performed on papers published up to April 2014. The presence of serum immunoglobulin G and immunoglobulin A was performed by enzyme-linked immunosorbent assay test. The detection of microbial DNA in total peripheral blood was performed by nested polymerase chain reaction. The meta-analysis showed that: 1) C. pneumoniae DNA in blood and brain are more common in schizophrenic patients; 2) there is association with parasitism by T. gondii, despite the existence of publication bias; and 3) herpes viruses were not more common in schizophrenic patients. In our sample only anti-Toxoplasma immunoglobulin G was more prevalent and may be a risk factor related to schizophrenia, with potential value for prevention.

Sexually dimorphic effects of prenatal exposure to lipopolysaccharide, and prenatal and postnatal exposure to propionic acid, on acoustic startle response and prepulse inhibition in adolescent rats: relevance to autism spectrum disorders

Potential environmental risk factors for autism spectrum disorders (ASD) include viral/bacterial infection and an altered microbiome composition. The present study investigated whether administration of immune and gastrointestinal factors during gestation and early life altered startle response and prepulse inhibition in adolescent offspring using lipopolysaccharide (LPS), a bacterial mimetic, and propionic acid (PPA), a short chain fatty acid and metabolic product of antibiotic resistant enteric bacteria. Pregnant Long-Evans rats were injected once a day with PPA (500 mg/kg SC) on G12-16, LPS (50 μg/kg SC) on G15 and G16, or vehicle control on G12-16 or G15-16. Male and female offspring were injected with PPA (500 mg/kg SC) or vehicle twice a day, every second day from postnatal days 10-18. Acoustic startle and prepulse inhibition was measured on postnatal days 45, 47, 49, and 51. Prenatal and postnatal treatments altered startle behavior in a sex-specific manner. Prenatal LPS treatment produced hyper-sensitivity to acoustic startle in males, but not females and did not alter prepulse inhibition. Subtle alterations in startle responses that disappeared with repeated trials occurred with prenatal PPA and postnatal PPA treatment in both male and female offspring. Prenatal PPA treatment decreased prepulse inhibition in females, but not males. Lastly, females receiving a double hit of PPA, prenatal and postnatal, showed sensitization to acoustic startle, providing evidence for the double hit hypothesis. The current study supports the hypotheses that immune activation and metabolic products of enteric bacteria may alter development and behavior in ways that resemble sensory abnormalities observed in ASD.

Deletion of olfactomedin 2 induces changes in the AMPA receptor complex and impairs visual, olfactory, and motor functions in mice

Olfactomedin 2 (Olfm2) is a secretory glycoprotein belonging to the family of olfactomedin domain-containing proteins. A previous study has shown that a mutation in OLFM2 is associated with primary open angle glaucoma in Japanese patients. In the present study, we generated Olfm2 deficient mice by replacing the Olfm2 gene with the LacZ gene. The loss of Olfm2 resulted in no gross abnormalities. However, Olfm2 null mice showed reduced exploration, locomotion, olfactory sensitivity, abnormal motor coordination, and anxiety related behavior. The pattern of the Olfm2 gene expression was studied in the brain and eye using β-galactosidase staining. In the brain, Olfm2 was mainly expressed in the olfactory bulb, cortex, piriform cortex, olfactory trabeculae, and inferior and superior colliculus. In the eye expression was detected mainly in retinal ganglion cells. In Olfm2 null mice, the amplitude of the first negative wave in the visual evoked potential test was significantly reduced as compared with wild-type littermates. Olfm2, similar to Olfm1, interacted with the GluR2 subunit of the AMPAR complexes and Olfm2 co-segregated with the AMPA receptor subunit GluR2 and other synaptic proteins in the synaptosomal membrane fraction upon biochemical fractionation of the adult mice cortex and retina. Immunoprecipitation from the synaptosomal membrane fraction of the Olfm2 null mouse brain cortex using the GluR2 antibody showed reduced levels of several components of the AMPAR complex in the immunoprecipitates including Olfm1, PSD95 and CNIH2. These results suggest that heterodimers of Olfm1 and Olfm2 interact with AMPAR more efficiently than Olfm2 homodimers and that Olfm2 plays a role in the organization of the AMPA receptor complexes.

Deletion in the N-terminal half of olfactomedin 1 modifies its interaction with synaptic proteins and causes brain dystrophy and abnormal behavior in mice

Olfactomedin 1 (Olfm1) is a secreted glycoprotein that is preferentially expressed in neuronal tissues. Here we show that deletion of exons 4 and 5 from the Olfm1 gene, which encodes a 52 amino acid long region in the N-terminal part of the protein, increased neonatal death and reduced body weight of surviving homozygous mice. Magnetic resonance imaging analyses revealed reduced brain volume and attenuated size of white matter tracts such as the anterior commissure, corpus callosum, and optic nerve. Adult Olfm1 mutant mice demonstrated abnormal behavior in several tests including reduced marble digging, elevated plus maze test, nesting activity and latency on balance beam tests as compared with their wild-type littermates. The olfactory system was both structurally and functionally disturbed by the mutation in the Olfm1 gene as shown by functional magnetic resonance imaging analysis and a smell test. Deficiencies of the olfactory system may contribute to the neonatal death and loss of body weight of Olfm1 mutant. Shotgun proteomics revealed 59 candidate proteins that co-precipitated with wild-type or mutant Olfm1 proteins in postnatal day 1 brain. Olfm1-binding targets included GluR2, Cav2.1, teneurin-4 and Kidins220. Modified interaction of Olfm1 with binding targets led to an increase in intracellular Ca(2+) concentration and activation of ERK1/2, MEK1 and CaMKII in the hippocampus and olfactory bulb of Olfm1 mutant mice compared with their wild-type littermates. Excessive activation of the CaMKII and Ras-ERK pathways in the Olfm1 mutant olfactory bulb and hippocampus by elevated intracellular calcium may contribute to the abnormal behavior and olfactory activity of Olfm1 mutant mice.

Maternal immune activation leads to age-related behavioral and immunological changes in male rat offspring - the effect of antipsychotic drugs

BACKGROUND

Prenatal immune system disturbances have been postulated to play an important role in pathogenesis of schizophrenia and related disorders. In the present study, we sought to answer the question whether behavioral changes in the neurodevelopmental model of schizophrenia in rats are accompanied by alterations in proliferative activity of splenocytes and pro- and anti-inflammatory cytokine levels. Furthermore, the effects of two antipsychotic drugs on these parameters were determined.

METHODS

Lipopolysaccharide (LPS) was administered subcutaneously to pregnant dams at a dose of 1 mg/kg every second day from the 7(th) day of pregnancy till delivery. Age-dependent behavioral and immunological changes were studied when control and prenatally LPS-pretreated offspring male rats were 30 and 90 days old. Chlorpromazine (10 mg/kg ip) or clozapine (10 mg/kg ip) was administered chronically (21 days) after behavioral verification to 3 months old offspring males. Changes in sensorimotor gating (prepulse inhibition, PPI), mitogen-induced proliferative activity of splenocytes ([(3)H]-thymidine incorporation) and cytokine levels (ELISA) were measured.

RESULTS

Prenatally LPS-pretreated rats showed PPI deficit only at 90 but not at 30 days of age, whereas an enhancement of mitogen-stimulated proliferative activity of splenocytes was observed in both time points. Additionally, the level of proinflammatory cytokines (IL-1β, IL-2, IL-6, TNF-α) in prenatally LPS-pretreated rats was enhanced when they were 30 days old and remained elevated in 90 days old offspring. No changes in IL-10 level were observed. Chronic administration of chlorpromazine or clozapine reduced the deficit in PPI deficit in prenatally LPS-treated rats. In the used model, chlorpromazine normalized both T and B lymphocyte proliferation, whereas clozapine B lymphocyte activity only. Moreover, both antipsychotics modulated the enhanced levels of IL-1β, IL-2 and TNF-α in the offspring of LPS-treated mothers.

CONCLUSIONS

This study indicates that in LPS-evoked model of schizophrenia, peripheral immunological changes are long-lasting and precede behavioral deficit. The disturbances in T cell-mediated immunity as well as cytokine production were attenuated by antipsychotic drug administration.

Disruption of social approach by MK-801, amphetamine, and fluoxetine in adolescent C57BL/6J mice

Autism is a severe neurodevelopmental disorder, diagnosed on the basis of core behavioral symptoms. Although the mechanistic basis for the disorder is not yet known, genetic analyses have suggested a role for abnormal excitatory/inhibitory signaling systems in brain, including dysregulation of glutamatergic neurotransmission. In mice, the constitutive knockdown of NMDA receptors leads to social deficits, repetitive behavior, and self-injurious responses that reflect aspects of the autism clinical profile. However, social phenotypes differ with age: mice with reduced NMDA-receptor function exhibit hypersociability in adolescence, but markedly deficient sociability in adulthood. The present studies determined whether acute disruption of NMDA neurotransmission leads to exaggerated social approach, similar to that observed with constitutive disruption, in adolescent C57BL/6J mice. The effects of MK-801, an NMDA receptor antagonist, were compared with amphetamine, a dopamine agonist, and fluoxetine, a selective serotonin reuptake inhibitor, on performance in a three-chamber choice task. Results showed that acute treatment with MK-801 led to social approach deficits at doses without effects on entry numbers. Amphetamine also decreased social preference, but increased number of entries at every dose. Fluoxetine (10 mg/kg) had selective effects on social novelty preference. Withdrawal from a chronic ethanol regimen decreased activity, but did not attenuate sociability. Low doses of MK-801 and amphetamine were also evaluated in a marble-burying assay for repetitive behavior. MK-801, at a dose that did not disrupt sociability or alter entries, led to a profound reduction in marble-burying. Overall, these findings demonstrate that moderate alteration of NMDA, dopamine, or serotonin function can attenuate social preference in wild type mice.

Behavioral animal models of antipsychotic drug actions

Basic research in animals represents a fruitful approach to study the neurobiological basis of brain and behavioral disturbances relevant to neuropsychiatric disease and to establish and evaluate novel pharmacological therapies for their treatment. In the context of schizophrenia, there are models employing specific experimental manipulations developed according to specific pathophysiological or etiological hypotheses. The use of selective lesions in adult animals and the acute administration of psychotomimetic agents are indispensable tools in the elucidation of the contribution of specific brain regions or neurotransmitters to the genesis of a specific symptom or collection of symptoms and enjoy some degrees of predictive validity. However, they may be inaccurate, if not inadequate, in capturing the etiological mechanisms or ontology of the disease needed for a complete understanding of the disease and may be limited in the discovery of novel compounds for the treatment of negative and cognitive symptoms of schizophrenia. Under the prevailing consensus of schizophrenia as a disease of neurodevelopmental origin, we have seen the establishment of neurodevelopmental animal models which aim to identify the etiological processes whereby the brain, following specific triggering events, develops into a "schizophrenia-like brain" over time. Many neurodevelopmental models such as the neonatal ventral hippocampus (vHPC) lesion, methylazoxymethanol (MAM), and prenatal immune activation models can mimic a broad spectrum of behavioral, cognitive, and pharmacological abnormalities directly implicated in schizophrenic disease. These models allow pharmacological screens against multiple and coexisting schizophrenia-related dysfunctions while incorporating the disease-relevant concept of abnormal brain development. The multiplicity of existing models is testimonial to the multifactorial nature of schizophrenia, and there are ample opportunities for their integration. Indeed, one ultimate goal must be to incorporate the successes of distinct models into one unitary account of the complex disorder of schizophrenia and to use such unitary approaches in the further development and evaluation of novel antipsychotic treatment strategies.