Adult behavioral and pharmacological dysfunctions following disruption of the fetal brain balance between pro-inflammatory and IL-10-mediated anti-inflammatory signaling

Modulation of schizophrenia-related genes in the forebrain of adolescent and adult rats exposed to maternal immune activation

Maternal immune activation (MIA) is an environmental risk factor for schizophrenia, and may contribute to other developmental disorders including autism and epilepsy. Activation of pro-inflammatory cytokine systems by injection of the synthetic double-stranded RNA polyriboinosinic-polyribocytidilic acid (Poly I:C) mediates important neurochemical and behavioral corollaries of MIA, which have relevance to deficits observed in schizophrenia. We examined the consequences of MIA on forebrain expression of neuregulin-1 (NRG-1), brain-derived neurotrophic factor (BDNF) and their receptors, ErbB4 and trkB, respectively, genes associated with schizophrenia. On gestational day 14, pregnant rats were injected with Poly I:C or vehicle. Utilizing in situ hybridization, expression of NRG-1, ErbB4, BDNF, and trkB was examined in male rat offspring at postnatal day (P) 14, P30 and P60. ErbB4 mRNA expression was significantly increased at P30 in the anterior cingulate (AC Ctx), frontal, and parietal cortices, with increases in AC Ctx expression continuing through P60. ErbB4 expression was also elevated in the prefrontal cortex (PFC) at P14. In contrast, NRG-1 mRNA was decreased in the PFC at P60. Expression of BDNF mRNA was significantly upregulated in the PFC at P60 and decreased in the AC Ctx at P14. Expression of trkB was increased in two regions, the piriform cortex at P14 and the striatum at P60. These findings demonstrate developmentally and regionally selective alterations in the expression of schizophrenia-related genes as a consequence of MIA. Further study is needed to determine contributions of these effects to the development of alterations of relevance to neuropsychiatric diseases.

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

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

Alterations in immune cells and mediators in the brain: it's not always neuroinflammation!

Neuroinflammation was once a clearly defined term denoting pathological immune processes within the central nervous system (CNS). Historically, this term was used to indicate the four hallmarks of peripheral inflammaton that occur following severe CNS injuries, such as stroke, injury or infection. Recently, however, the definition of neuroinflammation has relaxed to the point that it is often now assumed to be present when even only a single classical hallmark of inflammation is measured. As a result, a wide range of disorders, from psychiatric to degenerative diseases, are now assumed to have an integral inflammatory component. Ironically, at the same time, research has revealed unexpected nonclassical immune actions of immune mediators and cells in the CNS in the absence of pathology, increasing the likelihood that homeostatic and adaptive immune processes in the CNS will be mistaken for neuroinflammation. Thus, we suggest reserving the term neuroinflammation for contexts where multiple signs of inflammation are present to avoid erroneously classifying disorders as inflammatory when they may instead be caused by nonimmune etiologies or secondary immune processes that serve adaptive roles.

Long-term pathological consequences of prenatal infection: beyond brain disorders

Prenatal immunological adversities such as maternal infection have been widely acknowledged to contribute to an increased risk of neurodevelopmental brain disorders. In recent years, epidemiological and experimental evidence has accumulated to suggest that prenatal exposure to immune challenges can also negatively affect various physiological and metabolic functions beyond those typically associated with primary defects in CNS development. These peripheral changes include excessive accumulation of adipose tissue and increased body weight, impaired glycemic regulation and insulin resistance, altered myeloid lineage development, increased gut permeability, hyperpurinergia, and changes in microbiota composition. Experimental work in animal models further suggests that at least some of these peripheral abnormalities could directly contribute to CNS dysfunctions, so that normalization of peripheral pathologies could lead to an amelioration of behavioral deficits. Hence, seemingly unrelated central and peripheral effects of prenatal infection could represent interrelated pathological entities that emerge in response to a common developmental stressor. Targeting peripheral abnormalities may thus represent a valuable strategy to improve the wide spectrum of behavioral abnormalities that can emerge in subjects with prenatal infection histories.

The interaction between maternal immune activation and alpha 7 nicotinic acetylcholine receptor in regulating behaviors in the offspring

Mutation of human chromosome 15q13.3 increases the risk for autism and schizophrenia. One of the noteworthy genes in 15q13.3 is CHRNA7, which encodes the nicotinic acetylcholine receptor alpha 7 subunit (α7nAChR) associated with schizophrenia in clinical studies and rodent models. This study investigates the role of α7nAChR in maternal immune activation (MIA) mice model, a murine model of environmental risk factor for autism and schizophrenia. We provided choline, a selective α7nAChR agonist among its several developmental roles, in the diet of C57BL/6N wild-type dams throughout the gestation and lactation period and induced MIA at mid-gestation. The adult offspring behavior and gene expression profile in the maternal-placental-fetal axis at mid-gestation were investigated. We found that choline supplementation prevented several MIA-induced behavioral abnormalities in the wild-type offspring. Pro-inflammatory cytokine interleukin-6 (Il6) and Chrna7 gene expression in the wild-type fetal brain were elevated by poly(I:C) injection and were suppressed by gestational choline supplementation. We further investigated the gene expression level of Il6 in Chrna7 mutant mice. We found that the basal level of Il6 was higher in Chrna7 mutant fetal brain, which suggests that α7nAChR may serve an anti-inflammatory role in the fetal brain during development. Lastly, we induced MIA in Chrna7(+/-) offspring. The Chrna7(+/-) offspring were more vulnerable to MIA, with increased behavioral abnormalities. Our study shows that α7nAChR modulates inflammatory response affecting the fetal brain and demonstrates its effects on offspring behavior development after MIA.

Maternal lipopolysaccharide alters the newborn oxidative stress and C-reactive protein levels in response to an inflammatory stress

Maternal infection is associated with oxidative stress (OS) and inflammatory responses. We have previously shown that maternal exposure to lipopolysaccharide (LPS) at E18 alters the subsequent offspring immune response. As immune responses are mediated, in part, by OS, we sought to determine if maternal inflammation during pregnancy programs offspring OS and C-reactive protein (CRP) levels. Pregnant Sprague-Dawley rats received intraperitoneal (i.p.) injections of saline or LPS at 18 days' gestation (n = 4), and pups delivered spontaneously at term. At postnatal day 24, male and female offspring received i.p. injection of LPS. Serum lipid peroxides formation (PD) and CRP levels were determined before and at 4 h following the LPS injection. Pups of LPS-exposed dams had significantly higher basal OS (PD 29.4 ± 5.4 v. 10.1 ± 4.8 nmol/ml) compared with controls. In response to LPS, CRP levels (20.4 ± 2.8 v. 5.7 ± 1.0 ng/ml) were significantly higher among pups of LPS-exposed dams than controls. Prenatal maternal exposure to LPS increases baseline OS levels in neonates and CRP levels in response to LPS. These results suggest that maternal inflammation during the antenatal period may induce long-term sequelae in the offspring that may predispose to adult disease.

Neural targets in the study and treatment of social cognition in autism spectrum disorder

The purpose of this chapter is to present results from recent research on social cognition in autism spectrum disorder (ASD). The clinical phenomenology and neuroanatomical circuitry of ASD are first briefly described. The neuropharmacology of social cognition in animal models of ASD and humans is then addressed. Next, preclinical and clinical research on the neurohormone oxytocin is reviewed. This is followed by a presentation of results from preclinical and clinical studies on the excitatory amino acid glutamate. Finally, the role of neuroinflammation in ASD is addressed from the perspectives of preclinical neuroscience and research involving humans with ASD.

Protein deficiency and intestinal nematode infection in pregnant mice differentially impact fetal growth through specific stress hormones, growth factors, and cytokines

BACKGROUND

Protein deficiency (PD) and intestinal nematode infections commonly co-occur during pregnancy and impair fetal growth, but the complex network of signals has not been explored.

OBJECTIVE

Our objective was to assess those stress hormones, growth factors, and cytokines affected by maternal PD and nematode infection and associated with fetal growth.

METHODS

Using a 2 × 2 factorial design, CD-1 mice, fed protein-sufficient (PS; 24%) or protein-deficient (PD; 6%) isoenergetic diets, were either uninfected or infected every 5 d with Heligmosomoides bakeri, beginning on gestational day (GD) 5. Biomarker concentrations were measured on GD 18 in maternal serum (m), fetal serum (f), and amniotic fluid (af) by using Luminex.

RESULTS

Maternal PD lowered fetal body mass (PS/uninfected 1.25 ± 0.02 g, PS/infected 1.19 ± 0.02 g vs. PD/uninfected 1.11 ± 0.02 g, PD/infected 0.97 ± 0.02 g; P = 0.02), fetal lung (P = 0.005), and liver (P = 0.003) but not brain mass, whereas maternal infection lowered fetal length (PS/uninfected 2.28 ± 0.02 cm, PD/uninfected 2.27 ± 0.03 cm vs. PS/infected 2.21 ± 0.03 cm, PD/infected 2.11 ± 0.02 cm; P = 0.05) and kidney mass (P = 0.04). PD elevated stress hormones (m-adrenocortiotropic hormone, f-corticosterone, af-corticosterone) and reduced insulin-like growth factor 1 in all compartments (P ≤ 0.01), but these were unassociated with fetal mass or length. Fetal mass was positively associated with f-leptin (R(2) = 0.71, P = 0.0001) and negatively with fetal cytokines [tumor necrosis factor-α: R(2) = 0.62, P = 0.001; interleukin-4 (IL-4): R(2) = 0.63, P = 0.0004]. In contrast, maternal infection lowered f-prolactin (P = 0.02) that was positively associated with fetal length (R(2) = 0.43; P = 0.03); no other biomarker was affected by infection. Regression analyses showed associations between organ growth, cytokines, and growth factors: 1) thymus, spleen, heart, and brain with m-IL-10; 2) brain and kidney with f-vascular endothelial growth factor, af-monocyte chemotactic protein 1, af-interferon-γ, and af-eotaxin; and 3) liver and lung with f-leptin and af-corticosterone (all P ≤ 0.02).

CONCLUSIONS

PD and nematode infection impaired fetal mass and linear growth, respectively. Fetal mass, length, and individual organ masses were regulated by different hormones, growth factors, and cytokines.

Genetic Variants of Interleukin-10 Gene Promoter are Associated with Schizophrenia in Saudi Patients: A Case-Control Study

BACKGROUND

Interleukin-10 (IL-10) gene is considered as a potential candidate gene in schizophrenia association studies. The polymorphisms on IL-10 gene have been reported to be linked with susceptibility to the development of schizophrenia within consistent results.

AIMS

The aim of this case-control study was to examine whether the -1082A/G, -819T/C, and -592A/C polymorphisms in IL-10 gene are implicated in schizophrenia development in the Saudi population.

MATERIALS AND METHODS

Molecular genotyping of IL-10 gene polymorphisms was performed to analyze the genotypes and alleles distribution of three single-nucleotide polymorphisms (SNPs) in patients (n = 181) and healthy individuals as control group (n = 211).

RESULTS

The frequencies of GA genotype at -1082, and CC genotype at positions -592 and -819 were significantly higher in schizophrenia patients compared to healthy subjects suggesting that GA, CC, and CC genotypes are susceptible to schizophrenia. The ACC haplotype known to be associated with intermediate production of IL-10 are more prevalent in our schizophrenia patients. On the other hand, genotypes -1082 GG, -819 CT, and -592 CA of IL-10 were more prevalent in healthy controls suggesting protective effects of GA, CT, and CA genotypes against schizophrenia. There was no significant association of IL-10 polymorphisms with sex or positive or negative symptoms of schizophrenia.

CONCLUSION

This study indicates that the IL-10 gene polymorphisms play a significant role in the etiology of schizophrenia in Saudi Arabians patients.

Toward an immune-mediated subtype of autism spectrum disorder

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

Maternal immune activation and abnormal brain development across CNS disorders

Epidemiological studies have shown a clear association between maternal infection and schizophrenia or autism in the progeny. Animal models have revealed maternal immune activation (mIA) to be a profound risk factor for neurochemical and behavioural abnormalities in the offspring. Microglial priming has been proposed as a major consequence of mIA, and represents a critical link in a causal chain that leads to the wide spectrum of neuronal dysfunctions and behavioural phenotypes observed in the juvenile, adult or aged offspring. Such diversity of phenotypic outcomes in the mIA model are mirrored by recent clinical evidence suggesting that infectious exposure during pregnancy is also associated with epilepsy and, to a lesser extent, cerebral palsy in children. Preclinical research also suggests that mIA might precipitate the development of Alzheimer and Parkinson diseases. Here, we summarize and critically review the emerging evidence that mIA is a shared environmental risk factor across CNS disorders that varies as a function of interactions between genetic and additional environmental factors. We also review ongoing clinical trials targeting immune pathways affected by mIA that may play a part in disease manifestation. In addition, future directions and outstanding questions are discussed, including potential symptomatic, disease-modifying and preventive treatment strategies.

Aberrant fetal macrophage/microglial reactions to cytomegalovirus infection

Objective

Congenital cytomegalovirus (CMV) infection is the leading viral cause of neurodevelopmental disorders in humans, with the most severe and permanent sequelae being those affecting the cerebrum. As the fetal immune reactions to congenital CMV infection in the brain and their effects on cerebral development remain elusive, our aim was to investigate primitive innate immunity to CMV infection and its effects on cerebral corticogenesis in a mouse model for congenital CMV infection using a precise intraplacental inoculation method.

Methods

At 13.5 embryonic days (E13.5), pregnant C57BL/6 mice were intraplacentally infected with murine CMV (MCMV). Placentas and fetal organs were collected at 1, 3, and 5 days postinfection and analyzed.

Results

MCMV antigens were found frequently in perivascular macrophages, and subsequently in neural stem/progenitor cells (NSPCs). With increased expression of inducible nitric oxide synthase and proinflammatory cytokines, activated macrophages infiltrated into the infectious foci. In addition to the infected area, the numbers of both meningeal macrophages and parenchymal microglia increased even in the uninfected areas of MCMV-infected brain due to recruitment of their precursors from other sites. A bromodeoxyuridine (BrdU) incorporation experiment demonstrated that MCMV infection globally disrupted the self-renewal of NSPCs. Furthermore, BrdU-labeled neurons, particularly Brn2⁺ neurons of upper layers II/III in the cortical plate, decreased in number significantly in the MCMV-infected E18.5 cerebrum.

Interpretation

Brain macrophages are crucial for innate immunity during MCMV infection in the fetal brain, while their aberrant recruitment and activation may adversely impact on the stemness of NSPCs, resulting in neurodevelopmental disorders.

Insulin alleviates the inflammatory response and oxidative stress injury in cerebral tissues in septic rats

Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction that occurs secondary to infection in the body without overt central nervous system (CNS) infection. SAE is frequently encountered in critically ill patients in intensive care units and can be detected in up to 50–70% of septic patients. Previous studies have demonstrated that inflammatory cytokine release and oxidative stress injury are major pathophysiological mechanisms of SAE in critically ill patients. However, there are no effective strategies for the treatment of SAE. Insulin has important immunomodulatory effects and protective effects against oxidative stress injury in the peripheral organs of septic patients. However, very few studies of the possible effects of insulin in cerebral tissues of septic patients have been reported. Therefore, in this study, we aimed to explore whether insulin therapy can inhibit cytokine production (IL-1, IL-6, and TNF-a) and oxidative stress injury of the brain tissue in septic rats. We observed that the protein concentrations of IL-1, IL-6, and TNF-а, in addition to MDA and H₂O₂ were notably increased, inversely SOD, and GSH were sigificantly decreased in cortex, hippocampus, and hypothalamus of septic rats. Furthermore, the levels of S100 and NSE significantly increased. After 6 hours of insulin therapy, we found that the cytokine concentrations notably decreased and oxidative stress injuries in the cortex, hypothalamus, and hippocampus were alleviated in septic rats. In addition, the S100 and NSE levels significantly decreased. We concluded that insulin can inhibit the production of inflammatory cytokines and the oxidative stress response, thereby improving brain tissue damage.

Gender influence on schizophrenia-relevant abnormalities in a cuprizone demyelination model

The aim of this study was to determine whether early demyelination can impact behavior in young adulthood. For this purpose, albino Wistar rats of either sex were exposed to cuprizone (CPZ) in two different intoxication protocols: one group was intoxicated before weaning (CPZ-BW), from postnatal day 7 (P7) to P21, through maternal milk, whereas the other group was intoxicated after weaning (CPZ-AW), from P21 to P35. After treatment, rats were returned to a normal diet until P90 when behavioral studies were performed. Both treatments produced marked demyelination in the corpus callosum and retraction of cortical myelin fibers. The subsequent normal diet allowed for effective remyelination at P90. Interestingly, CPZ-AW correlated with significant behavioral and neurochemical changes in a gender-dependent manner. CPZ-AW treatment altered both the number of social activities and the latency to the first social interaction in males, while also highly compromising recognition-related activities. In addition, only P90 males treated AW showed a hyperdopaminergic striatum, confirmed by an increase in tyrosine hydroxylase expression and in dopamine levels. Our results suggest that the timing of demyelination significantly influences the development of altered behavior, particularly in adult males.

Maternal sleep deprivation inhibits hippocampal neurogenesis associated with inflammatory response in young offspring rats

Although sleep complaints are very common among pregnant women, the potential adverse effects of sleep disturbance on the offspring are not well studied. Growing evidence suggests that maternal stress can induce an inflammatory environment on the fetal development. But people are not sure about the consequences of prenatal stress such as the inflammatory responses induced by maternal sleep deprivation (MSD). In the present study, we investigated the effects of MSD on long-term behavioral and cognitive consequences in offspring and its underlying inflammatory response pathway. The pregnant Wistar rats received prolonged sleep deprivation (72h) on gestational day (GD) 4, 9, and 18, respectively. The post-natal day (PND) 21 offspring showed impaired hippocampus-dependent spatial learning and memory in the Morris Water Maze task and anhedonia in sucrose preference experiment. Quantification of BrdU(+) and DCX(+) cells revealed a significant decrease in hippocampus neurogenesis in prepuberty offspring, especially for the late MSD (GD 18) group. Real-time RT-PCR showed that after MSD, the expression of pro-inflammatory cytokines (IL-1β, IL-6 and TNFα) increased in the hippocampus of offspring on PND 1, 7, 14 and 21, whereas anti-inflammatory cytokine IL-10 reduced at the same time. Immunofluorescence found that the cells of activated microglia were higher in the brains of MSD offspring. Taken together, these results suggested that the MSD-induced inflammatory response is an important factor for neurogenesis impairment and neurobehavioral outcomes in prepuberty offspring.

Association of interleukin-10 polymorphisms with schizophrenia: a meta-analysis

BACKGROUND

The involvement of cytokines in schizophrenia (SZ) has been proposed in recent years and various studies have accumulated convergent lines of evidence. Among which, the role of interleukin-10 (IL-10) in SZ has been explored in a number of studies by investigating association of single nucleotide polymorphisms (SNPs) and susceptibility of SZ. However, the results are inconsistent since its power is limited by the individual sample size. To evaluate the overall effect between them, we conducted a meta-analysis by combining all available studies.

METHODS

Studies were searched from the database of PubMed, PsycINFO and ISI web of Knowledge up to Nov 2013. The meta-analysis was conducted based on statement of preferred reporting items for systematic reviews and meta-analyses (PRISMA).

RESULTS

Eleven studies including 6399 subjects (3129 cases and 3270 controls) were available for the meta-analysis. Among three investigated SNPs, rs1800872 was observed to be significantly associated with risk of SZ (AA vs. AC+CC, Pooled OR = 1.351, P-value  = 2.06E-04). Meanwhile, among six haplotypes of rs1800896 - rs1800871 - rs1800872, significant associations were observed in haplotype A-C-A (Pooled OR = 1.762, P-value  = 2.00E-03) and G-C-C (Pooled OR = 0.649, P-value  = 2.00E-03) for Asians. These results were still significant after adjusting for multiple comparisons.

CONCLUSIONS

This meta-analysis demonstrated an SNP and two haplotypes of IL-10 significantly associated with SZ, suggesting that IL-10 might be a risk factor of SZ.

Sarm1, a neuronal inflammatory regulator, controls social interaction, associative memory and cognitive flexibility in mice

Impaired neurodevelopment leads to several psychiatric disorders, including autism, schizophrenia and attention deficiency hyperactivity disorder. Our prior study showed that sterile alpha and TIR motif-containing 1 protein (Sarm1) regulates neuronal morphogenesis through at least two pathways. Sarm1 controls neuronal morphogenesis, including dendritic arborization, axonal outgrowth and establishment of neuronal polarity, through the MKK-JNK pathway. Neuronally expressed Sarm1 also regulates the expression of inflammatory cytokines in the brain, which have also been shown to impact brain development and function. Because the reduction of Sarm1 expression negatively influences neuronal development, here we investigated whether Sarm1 controls mouse behaviors. We analyzed two independent Sarm1 transgenic mouse lines using a series of behavioral assays, and found that the reduction of Sarm1 protein levels had a limited effect on locomotion and anxiety. However, Sarm1 knockdown mice exhibited impairments in cued and contextual fear conditioning as well as cognitive flexibility. Moreover, the three-chambered social test, reciprocal social interaction and social transmission of food preference further illustrated deficiencies in Sarm1 knockdown mice in social interaction. These findings suggest that Sarm1, a molecule that regulates innate immunity and neuronal morphogenesis, regulates social behaviors and cognition. We conclude that Sarm1 is involved in immune response, neural development and psychiatric disorders.

Prenatal immune activation induces maturation-dependent alterations in the prefrontal GABAergic transcriptome

Neuronal dysfunctions in the cortical GABAergic system have been widely documented in neuropsychiatric disorders with prenatal infectious etiologies, including schizophrenia. At least some of these abnormalities may stem from transcriptional impairments in the GABAergic transcriptome. However, the extent to which prenatal exposure to immune challenge can induce long-term alterations in GABAergic gene transcription remains largely elusive. Here, we use an established mouse model of prenatal immune activation induced by maternal gestational administration of the viral mimetic poly(I:C) (= polyriboinosinic-polyribocytidilic acid) to demonstrate that prenatal immune activation causes maturation-dependent alterations in prefrontal GABAergic gene expression. The spectrum of abnormalities included altered mRNA expression levels of enzymes regulating γ-aminobutyric acid (GABA) biosynthesis (glutamic acid decarboxylase 65-kDa [GAD65] and GAD67), vesicular GABA transporter (VGAT), alpha-subunits of the GABA(A) receptor (α2, α3, α4, and α5), and the chloride transporters sodium-potassium-chloride cotransporter 1 and potassium-chloride cotransporter 2. Additional western blot analyses confirmed the deficits in prefrontal GAD65/GAD67 and VGAT expression at the protein level. Intriguingly, the prefrontal GABAergic transcriptome was found to be more strongly affected in adult compared with peripubertal offspring born to immune-challenged mothers, and these age-dependent changes in GABAergic gene expression were paralleled by an adult onset of working memory deficiency. Collectively, our data emphasize a critical impact of prenatal immune-related insults on long-term GABAergic changes relevant to neuropsychiatric disorders with prenatal infectious etiologies, especially for those with delayed onset in early adulthood.

Prenatal poly(i:C) exposure and other developmental immune activation models in rodent systems

It is increasingly appreciated that altered neuroimmune mechanisms might play a role in the development of schizophrenia and related psychotic illnesses. On the basis of human epidemiological findings, a number of translational rodent models have been established to explore the consequences of prenatal immune activation on brain and behavioral development. The currently existing models are based on maternal gestational exposure to human influenza virus, the viral mimic polyriboinosinic-polyribocytidilic acid [Poly(I:C)], the bacterial endotoxin lipopolysaccharide, the locally acting inflammatory agent turpentine, or selected inflammatory cytokines. These models are pivotal for establishing causal relationships and for identifying cellular and molecular mechanisms that affect normal brain development in the event of early-life immune exposures. An important aspect of developmental immune activation models is that they allow a multi-faceted, longitudinal monitoring of the disease process as it unfolds during the course of neurodevelopment from prenatal to adult stages of life. An important recent refinement of these models is the incorporation of multiple etiologically relevant risk factors by combining prenatal immune challenges with specific genetic manipulations or additional environmental adversities. Converging findings from such recent experimental attempts suggest that prenatal infection can act as a "neurodevelopmental disease primer" that is likely relevant for a number of chronic mental illnesses. Hence, the adverse effects induced by prenatal infection might reflect an early entry into the neuropsychiatric route, but the specificity of subsequent disease or symptoms is likely to be strongly influenced by the genetic and environmental context in which the prenatal infectious process occurs.

Cytokines and the neurodevelopmental basis of mental illness

Epidemiological studies suggest that prenatal exposure to different types of viral or bacterial infections may be associated with similar outcomes; i.e., an increased risk of mental illness disorders in the offspring. Infections arising from various causes have similar debilitating effects in later life, suggesting that the exact pathogen may not be the critical factor in determining the neurological and cognitive outcome in the offspring. Instead, it is thought that response of the innate immune system, specifically the increased production of inflammatory cytokines, may be the critical mediator in altering fetal brain development pre-disposing the offspring to mental illness disorders later in life. Inflammatory cytokines are essential for normal brain development. Factors such as the site of cytokine production, a change in balance between anti- and pro- inflammatory cytokines, placental transfer of cytokines, the effects of cytokines on glial cells, and the effects of glucocorticoids are important when evaluating the impact of maternal infection on fetal brain development. Although it is clear that cytokines are altered in the fetal brain following maternal infection, further evidence is required to determine if cytokines are the critical factor that alters the trajectory of brain development, subsequently leading to postnatal behavioral and neurological abnormalities.

Maternal inflammation promotes fetal microglial activation and increased cholinergic expression in the fetal basal forebrain: role of interleukin-6

BACKGROUND

Perinatal exposure to infectious agents with associated maternal immune activation (MIA) leads to neuroanatomical and behavioral dysregulation reminiscent of autism spectrum disorders. Persistent microglial activation as well as increased choline acetyltransferase (ChAT) activity in the basal forebrain (BF) are characteristic of autistic subjects. Previous studies have shown that medium from activated microglia promotes cholinergic differentiation of precursors in the BF. We sought to determine whether MIA in vivo would lead to a similar effect on developing BF neurons.

METHODS

Pregnant mice were treated with the viral mimic polyinosinic-polycytidylic acid (poly(I:C)) or saline.

RESULTS

Poly(I:C) treatment resulted in increased production of cytokines and chemokines in fetal microglia and increased ChAT activity and cholinergic cell number in the perinatal BF. Whether microglial activation causes these changes is unclear. Examination of fetal brains from mice lacking interleukin-6 (IL-6 KOs) revealed an elevation in non-microglial-derived cytokines and chemokines over wild-type controls. Moreover, IL-6 KO offspring showed an elevation of ChAT activity even in the absence of poly(I:C) administration.

CONCLUSION

These data suggest that elevations in cytokines and/or chemokines caused either by maternal poly(I:C) administration or by the absence of IL-6 are associated with alterations in cholinergic development in the BF.

Enhanced hippocampal neuronal excitability and LTP persistence associated with reduced behavioral flexibility in the maternal immune activation model of schizophrenia

Individuals with schizophrenia display a number of structural and cytoarchitectural alterations in the hippocampus, suggesting that other functions such as synaptic plasticity may also be modified. Altered hippocampal plasticity is likely to affect memory processing, and therefore any such pathology may contribute to the cognitive symptoms of schizophrenia, which includes prominent memory impairment. The current study tested whether prenatal exposure to infection, an environmental risk factor that has previously been associated with schizophrenia produced changes in hippocampal synaptic transmission or plasticity, using the maternal immune activation (MIA) animal model. We also assessed performance in hippocampus-dependent memory tasks to determine whether altered plasticity is associated with memory dysfunction. MIA did not alter basal synaptic transmission in either the dentate gyrus or CA1 of freely moving adult rats. It did, however, result in increased paired-pulse facilitation of the dentate gyrus population spike and an enhanced persistence of dentate long-term potentiation. MIA animals displayed slower learning of a reversed platform location in the water maze, and a similarly slowed learning during reversal in a spatial plus maze task. Together these findings are indicative of reduced behavioral flexibility in response to changes in task requirements. The results are consistent with the hypothesis that hippocampal plasticity is altered in schizophrenia, and that this change in plasticity mechanisms may underlie some aspects of cognitive dysfunction in this disorder.

The effect of venovenous extra-corporeal membrane oxygenation (ECMO) therapy on immune inflammatory response of cerebral tissues in porcine model

Background

Extra-Corporeal Membrane Oxygenation (ECMO) therapy is associated with high risk of neurologic injury. But the mechanism of neurologic injury during and/or after ECMO therapy is still unclear. Recent animal experiments confirmed that ECMO treatment increases the immune inflammatory response. The aim of this study is to investigate the effect of VV- ECMO on immune inflammatory response of cerebral tissues and neurological impairment.

Methods

18 porcine were randomly divided into control, sham and ECMO group (n = 6/group). ECMO was run 24 h in the ECMO group, and serum collected at 0, 2, 6, 12 and 24 h during ECMO treatment for the analysis of cytokine (IL-1β, IL-6, IL-10, TNF-a) and cerebral injury specific biomarker S100B and NSE. After 24 h ECMO treatment, all animals were euthanized and cerebral tissues (hypothalamus, hippocampus and cortex) were collected for measure of mRNA and protein levels of cytokine (IL-1β, IL-6, IL-10, TNF-a).

Results

The results during ECMO treatment showed that all the pro-inflammation cytokines were increased significantly after 2 h, and anti-inflammation IL-10 showed transient hoist in the first 2 h in serum. After 24 h ECMO therapy, the mRNA levels of pro-inflammation cytokines and anti-inflammation IL-10 were simultaneously up-regulated in cerebral tissues (hypothalamus, hippocampus and cortex). And protein concentrations also showed different increasing levels in cerebral tissues. However, during the ECMO treatment, S100B and NSE protein in serum did not change significantly.

Conclusion

These findings suggest VV-ECMO treatment can not only lead to immune inflammatory response in blood, but can also produce immune and inflammatory response in cerebral tissues. However the extent of immune inflammation was not sufficient to cause significant neurological impairment in this study. But the correlation between cerebral inflammatory response and cerebral impairment need to further explore.

Soluble ST2 in the fetal inflammatory response syndrome: in vivo evidence of activation of the anti-inflammatory limb of the immune response

OBJECTIVE

Inflammation is a mechanism of host response to infection, which can be harmful when inappropriately modulated. Soluble ST2 (sST2) is a decoy receptor of interleukin (IL)-33, and this complex modulates the balance in the Th1/Th2 immune response. Moreover, sST2 inhibits the production of pro-inflammatory cytokines in cooperation with an anti-inflammatory cytokine, IL-10. The objectives of this study were to: (1) determine whether umbilical cord plasma sST2 concentration differs between preterm neonates with and without funisitis and between those with and without the fetal inflammatory response syndrome (FIRS); and (2) evaluate the relationship between sST2 and IL-10 among neonates with funisitis and/or FIRS.

METHODS

Umbilical cord plasma was collected from neonates delivered prematurely due to preterm labor or preterm prelabor rupture of membranes with (n = 36), and without funisitis (n = 30). FIRS (umbilical cord IL-6 concentration ≥ 17.5 pg/mL) was identified in 29 neonates. Plasma sST2 and IL-10 concentrations were determined by enzyme linked immune sorbent assay.

RESULTS

The median umbilical cord plasma sST2 concentration was 6.7-fold higher in neonates with FIRS than in those without FIRS (median 44.6 ng/mL, interquartile range (IQR) 13.8-80.3 ng/mL versus median 6.7 ng/mL, IQR 5.6-20.1 ng/mL; p < 0.0001). Similarly, the median umbilical cord plasma sST2 concentration was 2.7-fold higher in neonates with funisitis than in those without funisitis (median 19.1 ng/mL; IQR 7.1-75.0 ng/mL versus median 7.2 ng/mL; IQR 5.9-23.1 ng/mL; p = 0.008). There was a strong positive correlation between sST2 and IL-10 in neonates with funisitis and/or FIRS (Spearman's Rho = 0.7, p < 0.0001).

CONCLUSION

FIRS and funisitis are associated with an elevation of umbilical cord plasma concentrations of soluble ST2. This protein represents an important mediator of the immune response in neonates diagnosed with FIRS by promoting an anti-inflammatory effect in association with IL-10.

Epigenetic changes at gene promoters in response to immune activation in utero

Increasing evidence suggests that maternal infection increases the risk of psychiatric disorders, such as schizophrenia and autism in offspring. However, the molecular mechanisms associated with these effects are unclear. Here, we have studied epigenetic gene regulation in mice exposed to non-specific immune activation elicited by polyI:C injection to pregnant dams. Using Western blot analysis, we detected global hypoacetylation of histone H3, at lysine residues 9 and 14, and histone H4, at lysine residue 8, in the cortex from juvenile (∼24days of age) offspring exposed to polyI:C in utero, but not from adult (3months of age) offspring, which exhibit significant behavioral abnormalities. Accordingly, we detected robust deficits in the expression of genes associated with neuronal development, synaptic transmission and immune signaling in the cortex of polyI:C-exposed juvenile mice. In particular, we found that several genes in the glutamate receptor signaling pathway, including Gria1 and Slc17a7, showed decreases in promoter-specific histone acetylation, and corresponding gene expression deficits, in polyI:C-exposed offspring at both juvenile and adult ages. In contrast, the expression of these same genes, in addition to Disc1 and Ntrk3, was elevated in the hippocampus of juvenile mice, in concordance with elevated levels of promoter-specific histone acetylation. We suggest that these early epigenetic changes contribute to the delayed behavioral abnormalities that are observed in adult animals after exposure to polyI:C, and which resemble symptoms seen in schizophrenia and related disorders.

Schizophrenia: linking prenatal infection to cytokines, the tryptophan catabolite (TRYCAT) pathway, NMDA receptor hypofunction, neurodevelopment and neuroprogression

In 1995, the macrophage-T lymphocyte theory of schizophrenia (Smith and Maes, 1995) considered that activated immuno-inflammatory pathways may account for the higher neurodevelopmental pathology linked with gestational infections through the detrimental effects of activated microglia, oxidative and nitrosative stress (O&NS), cytokine-induced activation of the tryptophan catabolite (TRYCAT) pathway and consequent modulation of the N-methyl d-aspartate receptor (NMDAr) and glutamate production. The aim of the present paper is to review the current state-of-the art regarding the role of the above pathways in schizophrenia. Accumulating data suggest a powerful role for prenatal infection, both viral and microbial, in driving an early developmental etiology to schizophrenia. Models of prenatal rodent infection show maintained activation of immuno-inflammatory pathways coupled to increased microglia activation. The ensuing activation of immuno-inflammatory pathways in schizophrenia may activate the TRYCAT pathway, including increased kynurenic acid (KA) and neurotoxic TRYCATs. Increased KA, via the inhibition of the α7 nicotinic acetylcholine receptor, lowers gamma-amino-butyric-acid (GABA)ergic post-synaptic current, contributing to dysregulated glutamatergic activity. Hypofunctioning of the NMDAr on GABAergic interneurons will contribute to glutamatergic dysregulation. Many susceptibility genes for schizophrenia are predominantly expressed in early development and will interact with these early developmental driven changes in the immuno-inflammatory and TRYCAT pathways. Maternal infection and subsequent immuno-inflammatory responses are additionally associated with O&NS, including lowered antioxidants such as glutathione. This will contribute to alterations in neurogenesis and myelination. In such a scenario a) a genetic or epigenetic potentiation of immuno-inflammatory pathways may constitute a double hit on their own, stimulating wider immuno-inflammatory responses and thus potentiating the TRYCAT pathway and subsequent NMDAr dysfunction and neuroprogression; and b) antipsychotic-induced changes in immuno-inflammatory, TRYCAT and O&NS pathways would modulate the CNS glia-neuronal interactions that determine synaptic plasticity as well as myelin generation and maintenance.

Viral infection, inflammation and schizophrenia

Schizophrenia is a severe neurodevelopmental disorder with genetic and environmental etiologies. Prenatal viral/bacterial infections and inflammation play major roles in the genesis of schizophrenia. In this review, we describe a viral model of schizophrenia tested in mice whereby the offspring of mice prenatally infected with influenza at E7, E9, E16, and E18 show significant gene, protein, and brain structural abnormalities postnatally. Similarly, we describe data on rodents exposed to bacterial infection or injected with a synthetic viral mimic (PolyI:C) also demonstrating brain structural and behavioral abnormalities. Moreover, human serologic data has been indispensible in supporting the viral theory of schizophrenia. Individuals born seropositive for bacterial and viral agents are at a significantly elevated risk of developing schizophrenia. While the specific mechanisms of prenatal viral/bacterial infections and brain disorder are unclear, recent findings suggest that the maternal inflammatory response may be associated with fetal brain injury. Preventive and therapeutic treatment options are also proposed. This review presents data related to epidemiology, human serology, and experimental animal models which support the viral model of schizophrenia.

Developmental neuroinflammation and schizophrenia

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

Prenatal inflammation and neurodevelopment in schizophrenia: a review of human studies

A confluence of evidence supports an association between prenatal inflammation and risk of schizophrenia. Outside of studies of prenatal infections and risk of schizophrenia, other relevant human studies of prenatal inflammation and neurodevelopment in schizophrenia have not been reviewed. In this paper, we review human studies of 1) prenatal inflammation and risk of schizophrenia, 2) inflammation as a potential common mediator of several prenatal risk factors for schizophrenia other than prenatal infections, 3) prenatal inflammation and immune function, neurocognition, brain morphology, and gene expression in adult offspring with schizophrenia, and 4) gene by environment and gene by gene interactions relevant to these associations. We suggest future areas for human studies research based on existing findings.

Prenatal stress induces schizophrenia-like alterations of serotonin 2A and metabotropic glutamate 2 receptors in the adult offspring: role of maternal immune system

It has been suggested that severe adverse life events during pregnancy increase the risk of schizophrenia in the offspring. The serotonin 5-HT(2A) and the metabotropic glutamate 2 (mGlu2) receptors both have been the target of considerable attention regarding schizophrenia and antipsychotic drug development. We tested the effects of maternal variable stress during pregnancy on expression and behavioral function of these two receptors in mice. Prenatal stress increased 5-HT(2A) and decreased mGlu2 expression in frontal cortex, a brain region involved in perception, cognition, and mood. This pattern of expression of 5-HT(2A) and mGlu2 receptors was consistent with behavioral alterations, including increased head-twitch response to the hallucinogenic 5-HT(2A) agonist DOI [1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane] and decreased mGlu2-dependent antipsychotic-like effect of the mGlu2/3 agonist LY379268 (1R,4R,5S,6R-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate) in adult, but not prepubertal, mice born to stressed mothers during pregnancy. Cross-fostering studies determined that these alterations were not attributable to effects of prenatal stress on maternal care. Additionally, a similar pattern of biochemical and behavioral changes were observed in mice born to mothers injected with polyinosinic:polycytidylic acid [poly(I:C)] during pregnancy as a model of prenatal immune activation. These data strengthen pathophysiological hypotheses that propose an early neurodevelopmental origin for schizophrenia and other psychiatric disorders.

Penehyclidine hydrochloride attenuates the cerebral injury in a rat model of cardiopulmonary bypass

This study investigated the effect of penehyclidine hydrochloride (PHC) on regulatory mediators during the neuroinflammatory response and cerebral cell apoptosis following cardiopulmonary bypass (CPB). Forty-eight rats were randomly divided among 4 groups as follows: sham-operation, vehicle, low-dose PHC (0.6 mg·(kg body mass)(-1)), and high-dose PHC (2.0 mg·(kg body mass)(-1)). CPB was performed in the latter 3 groups. The plasma levels of neuron specific enolase (NSE) and S-100B were tested with ELISA. Real-time PCR and Western blotting were used to evaluate the expression levels of matrix metalloproteinase-9 (MMP-9), IL-10, caspase-3, Bcl-2, and p38 in brain tissue. The ultrastructure of hippocampus tissue was examined under an electron microscope. PHC attenuated the increase of plasma NSE and S-100B following CPB. MMP-9, cleaved caspase-3, and phosphorylated p38 expression were substantially increased in the vehicle group compared with the sham-operation group and gradually diminished with increasing doses of PHC. IL-10 and Bcl-2 expression were markedly lower in the vehicle group than in the sham-operation group and gradually recovered with increasing doses of PHC. PHC attenuated the histopathological changes of cerebral injury following CPB. PHC favorably regulates the inflammatory response and reduces markers of neuronal injury following CPB, potentially by reducing p38 and caspase-3 activation.

Stress in puberty unmasks latent neuropathological consequences of prenatal immune activation in mice

Prenatal infection and exposure to traumatizing experiences during peripuberty have each been associated with increased risk for neuropsychiatric disorders. Evidence is lacking for the cumulative impact of such prenatal and postnatal environmental challenges on brain functions and vulnerability to psychiatric disease. Here, we show in a translational mouse model that combined exposure to prenatal immune challenge and peripubertal stress induces synergistic pathological effects on adult behavioral functions and neurochemistry. We further demonstrate that the prenatal insult markedly increases the vulnerability of the pubescent offspring to brain immune changes in response to stress. Our findings reveal interactions between two adverse environmental factors that have individually been associated with neuropsychiatric disease and support theories that mental illnesses with delayed onsets involve multiple environmental hits.

Research review: maternal prenatal distress and poor nutrition - mutually influencing risk factors affecting infant neurocognitive development

BACKGROUND

Accumulating data from animal and human studies indicate that the prenatal environment plays a significant role in shaping children's neurocognitive development. Clinical, epidemiologic, and basic science research suggests that two experiences relatively common in pregnancy - an unhealthy maternal diet and psychosocial distress - significantly affect children's future neurodevelopment. These prenatal experiences exert their influence in the context of one another and yet, almost uniformly, are studied independently.

SCOPE AND METHOD OF REVIEW

In this review, we suggest that studying neurocognitive development in children in relation to both prenatal exposures is ecologically most relevant, and methodologically most sound. To support this approach, we selectively review two research topics that demonstrate the need for dual exposure studies, including exemplar findings on (a) the associations between pregnant women's inadequate maternal intake of key nutrients - protein, fat, iron, zinc, and choline - as well as distress in relation to overlapping effects on children's neurocognitive development; and (b) cross-talk between the biology of stress and nutrition that can amplify each experience for the mother and fetus,. We also consider obstacles to this kind of study design, such as questions of statistical methods for 'disentangling' the exposure effects, and aim to provide some answers.

CONCLUSION

Studies that specifically include both exposures in their design can begin to determine the relative and/or synergistic impact of these prenatal experiences on developmental trajectories - and thereby contribute most fully to the understanding of the early origins of health and disease.

Exploring the pathogenetic association between schizophrenia and type 2 diabetes mellitus diseases based on pathway analysis

BACKGROUND

Schizophrenia (SCZ) and type 2 diabetes mellitus (T2D) are both complex diseases. Accumulated studies indicate that schizophrenia patients are prone to present the type 2 diabetes symptoms, but the potential mechanisms behind their association remain unknown. Here we explored the pathogenetic association between SCZ and T2D based on pathway analysis and protein-protein interaction.

RESULTS

With sets of prioritized susceptibility genes for SCZ and T2D, we identified significant pathways (with adjusted p-value < 0.05) specific for SCZ or T2D and for both diseases based on pathway enrichment analysis. We also constructed a network to explore the crosstalk among those significant pathways. Our results revealed that some pathways are shared by both SCZ and T2D diseases through a number of susceptibility genes. With 382 unique susceptibility proteins for SCZ and T2D, we further built a protein-protein interaction network by extracting their nearest interacting neighbours. Among 2,104 retrieved proteins, 364 of them were found simultaneously interacted with susceptibility proteins of both SCZ and T2D, and proposed as new candidate risk factors for both diseases. Literature mining supported the potential association of partial new candidate proteins with both SCZ and T2D. Moreover, some proteins were hub proteins with high connectivity and interacted with multiple proteins involved in both diseases, implying their pleiotropic effects for the pathogenic association. Some of these hub proteins are the components of our identified enriched pathways, including calcium signaling, g-secretase mediated ErbB4 signaling, adipocytokine signaling, insulin signaling, AKT signaling and type II diabetes mellitus pathways. Through the integration of multiple lines of information, we proposed that those signaling pathways, which contain susceptibility genes for both diseases, could be the key pathways to bridge SCZ and T2D. AKT could be one of the important shared components and may play a pivotal role to link both of the pathogenetic processes.

CONCLUSIONS

Our study is the first network and pathway-based systematic analysis for SCZ and T2D, and provides the general pathway-based view of pathogenetic association between two diseases. Moreover, we identified a set of candidate genes potentially contributing to the linkage between these two diseases. This research offers new insights into the potential mechanisms underlying the co-occurrence of SCZ and T2D, and thus, could facilitate the inference of novel hypotheses for the co-morbidity of the two diseases. Some etiological factors that exert pleiotropic effects shared by the significant pathways of two diseases may have important implications for the diseases and could be therapeutic intervention targets.

Microglia in development: linking brain wiring to brain environment

Microglia are enigmatic non-neuronal cells that infiltrate and take up residence in the brain during development and are thought to perform a surveillance function. An established literature has documented how microglia are activated by pathogenic stimuli and how they contribute to and resolve injuries to the brain. However, much less work has been aimed at understanding their function in the uninjured brain. A series of recent in vivo imaging studies shows that microglia in their resting state are highly motile and actively survey their neuronal surroundings. Furthermore, new data suggest that microglia in their resting state are able to phagocytose unwanted synapses and in this way contribute to synaptic pruning and maturation during development. Coupled with their exquisite sensitivity to pathogenic stimuli, these data suggest that microglia form a link that couples changes in brain environment to changes in brain wiring. Here we discuss this hypothesis and propose a model for the role of microglia during development in sculpting brain connectivity.

Leptin and interleukin-6 alter the function of mesolimbic dopamine neurons in a rodent model of prenatal inflammation

Maternal inflammation during critical stages of gestation is thought to underlie the link between prenatal infection and several neurodevelopmental psychiatric disorders in the offspring, including schizophrenia. Increased activity of mesolimbic dopamine (DA) neurons, a hallmark of psychosis, is found in offspring of rodents exposed to a prenatal inflammatory challenge but it is unclear how this effect is elicited. Using an experimental model of localized aseptic inflammation with turpentine oil (TURP) we sought to establish whether circulating interleukin-6 (IL-6) and leptin play a role in the effects of prenatal inflammation on DA neurons. Both mediators are involved in the systemic inflammatory response to immunogens, with IL-6 mediating the early phase, followed by leptin in the late phase of the response. Maternal treatment with TURP at gestational day (GD) 15 enhanced the locomotor response to the DA indirect agonist, amphetamine (AMPH), increased the expression of tyrosine hydroxylase (TH), an enzyme involved in DA synthesis, DA levels and the expression of the post-synaptic protein spinophilin in the nucleus accumbens (NAcc) in the adult offspring. All of these alterations were totally abolished by co-treating the pregnant dams with a neutralizing IL-6 antiserum. Neutralization of maternal leptin prevented the enhanced behavioral sensitization and elevation of DA and spinophilin in the NAcc but spared other changes regulated by IL-6, such as increased NAcc TH levels and acute locomotor response to AMPH. Our results provide novel evidence to suggest that prenatal surges in both maternal circulating IL-6 and leptin contribute to the appearance of sensitized DA function in the adult offspring.

Interleukin-19 in fetal systemic inflammation

OBJECTIVE

The fetal inflammatory response syndrome (FIRS) is considered the fetal counterpart of the systemic inflammatory response syndrome (SIRS), which can be caused by infection and non-infection-related insults. Although the initial response is mediated by pro-inflammatory signals, the control of this response is achieved by anti-inflammatory mediators which are essential for the successful outcome of the affected individual. Interleukin (IL)-19 is capable of stimulating the production of IL-10, a major anti-inflammatory cytokine, and is a potent inducer of the T-helper 2 (Th2) response. The aim of this study was to determine if there is a change in umbilical cord plasma IL-19 and IL-10 concentrations in preterm neonates with and without acute funisitis, the histologic counterpart of FIRS.

METHODS

A case-control study was conducted including 80 preterm neonates born after spontaneous labor. Neonates were classified according to the presence (n = 40) or absence of funisitis (n = 40), which is the pathologic hallmark of FIRS. Neonates in each group were also matched for gestational age. Umbilical cord plasma IL-19 and IL-10 concentrations were determined by ELISA.

RESULTS

1) The median umbilical cord plasma IL-19 concentration was 2.5-fold higher in neonates with funisitis than in those without funisitis (median 87 pg/mL; range 20.6-412.6 pg/mL vs. median 37 pg/mL; range 0-101.7 pg/mL; p < 0.001); 2) newborns with funisitis had a significantly higher median umbilical cord plasma IL-10 concentration than those without funisitis (median 4 pg/mL; range 0-33.5 pg/mL vs. median 2 pg/mL; range 0-13.8 pg/mL; p < 0.001); and 3) the results were similar when we included only patients with funisitis who met the definition of FIRS by umbilical cord plasma IL-6 concentrations ≥ 17.5 pg/mL (p < 0.001).

CONCLUSION

IL-19 and IL-10 are parts of the immunologic response of FIRS. A subset of fetuses with FIRS had high umbilical cord plasma IL-19 concentrations. In utero exposure to high systemic concentrations of IL-19 may reprogram the immune response.

Maternal immune activation by poly I:C induces expression of cytokines IL-1β and IL-13, chemokine MCP-1 and colony stimulating factor VEGF in fetal mouse brain

Background

Maternal viral infection during pregnancy is associated with an increase in the incidence of psychiatric disorders with presumed neurodevelopmental origin, including autism spectrum disorders and schizophrenia. The enhanced risk for developing mental illness appears to be caused by deleterious effects of innate immune response-associated factors on the development of the central nervous system, which predispose the offspring to pathological behaviors in adolescence and adulthood. To identify the immune response-associated soluble factors that may affect central nervous system development, we examined the effect of innate immune response activation by polyriboinosinic-polyribocytidylic acid (poly(I:C)), a synthetic analogue of viral double-stranded RNA, on the expression levels of pro- and anti-inflammatory cytokines, chemokines and colony stimulating factors in fetal and postnatal mouse brain 6 h and 24 h after treatment.

Methods

C57BL/6J pregnant mice (gestational day 16) or newborn mice (postnatal day 4) received a single intraperitoneal injection of the synthetic analogue of viral double-stranded RNA poly(I:C) (20 mg/kg). Thirty-two immune response-associated soluble factors, including pro- and anti-inflammatory cytokines, chemokines and colony stimulating factors, were assayed 6 h and 24 h after poly(I:C) injection using multiplexed bead-based immunoassay (Milliplex Map) and processed in a Luminex 100 IS instrument.

Results

Maternal exposure to poly(I:C) at gestational day 16 induced a significant increase in cytokines interleukin (IL)-1β, IL-7 and IL-13; chemokines monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein (MIP)-1α, interferon gamma-induced protein (IP)-10 and monokine induced by IFN-gamma (MIG); and in the colony stimulating factor vascular endothelial growth factor (VEGF) in the fetal brain. IL-1β showed the highest concentration levels in fetal brains and was the only cytokine significantly up-regulated 24 h after maternal poly(I:C) injection, suggesting that IL-1β may have a deleterious impact on central nervous system development. In contrast, poly(I:C) treatment of postnatal day 4 pups induced a pronounced rise in chemokines and colony stimulating factors in their brains instead of the pro-inflammatory cytokine IL-1β.

Conclusions

This study identified a significant increase in the concentration levels of the cytokines IL-1β and IL-13, the chemokine MCP-1 and the colony stimulating factor VEGF in the developing central nervous system during activation of an innate immune response, suggesting that these factors are mediators of the noxious effects of maternal immune activation on central nervous system development, with potential long-lasting effects on animal behavior.

Animal models of prenatal immune challenge and their contribution to the study of schizophrenia: a systematic review

Prenatal immune challenge (PIC) in pregnant rodents produces offspring with abnormalities in behavior, histology, and gene expression that are reminiscent of schizophrenia and autism. Based on this, the goal of this article was to review the main contributions of PIC models, especially the one using the viral-mimetic particle polyriboinosinic-polyribocytidylic acid (poly-I:C), to the understanding of the etiology, biological basis and treatment of schizophrenia. This systematic review consisted of a search of available web databases (PubMed, SciELO, LILACS, PsycINFO, and ISI Web of Knowledge) for original studies published in the last 10 years (May 2001 to October 2011) concerning animal models of PIC, focusing on those using poly-I:C. The results showed that the PIC model with poly-I:C is able to mimic the prodrome and both the positive and negative/cognitive dimensions of schizophrenia, depending on the specific gestation time window of the immune challenge. The model resembles the neurobiology and etiology of schizophrenia and has good predictive value. In conclusion, this model is a robust tool for the identification of novel molecular targets during prenatal life, adolescence and adulthood that might contribute to the development of preventive and/or treatment strategies (targeting specific symptoms, i.e., positive or negative/cognitive) for this devastating mental disorder, also presenting biosafety as compared to viral infection models. One limitation of this model is the incapacity to model the full spectrum of immune responses normally induced by viral exposure.

Prenatal immune activation interacts with genetic Nurr1 deficiency in the development of attentional impairments

Prenatal exposure to infection has been linked to increased risk of neurodevelopmental brain disorders, and recent evidence implicates altered dopaminergic development in this association. However, since the relative risk size of prenatal infection appears relatively small with respect to long-term neuropsychiatric outcomes, it is likely that this prenatal insult interacts with other factors in shaping the risk of postnatal brain dysfunctions. In the present study, we show that the neuropathological consequences of prenatal viral-like immune activation are exacerbated in offspring with genetic predisposition to dopaminergic abnormalities induced by mutations in Nurr1, a transcription factor highly essential for normal dopaminergic development. We combined a mouse model of heterozygous genetic deletion of Nurr1 with a model of prenatal immune challenge by the viral mimetic poly(I:C) (polyriboinosinic polyribocytidilic acid). In our gene-environment interaction model, we demonstrate that the combination of the genetic and environmental factors not only exerts additive effects on locomotor hyperactivity and sensorimotor gating deficits, but further produces synergistic effects in the development of impaired attentional shifting and sustained attention. We further demonstrate that the combination of the two factors is necessary to trigger maldevelopment of prefrontal cortical and ventral striatal dopamine systems. Our findings provide evidence for specific gene-environment interactions in the emergence of enduring attentional impairments and neuronal abnormalities pertinent to dopamine-associated brain disorders such as schizophrenia and attention deficit/hyperactivity disorder, and further emphasize a critical role of abnormal dopaminergic development in these etiopathological processes.

Inflammation during fetal and neonatal life: implications for neurologic and neuropsychiatric disease in children and adults

Inflammation is increasingly recognized as being of both physiological and pathological importance in the immature brain. The rationale of this review is to present an update on this topic with focus on long-term consequences of inflammation during childhood and in adults. The immature brain can be exposed to inflammation in connection with viral or bacterial infection during pregnancy or as a result of sterile central nervous system (CNS) insults. Through efficient anti-inflammatory and reparative processes, inflammation may resolve without any harmful effects on the brain. Alternatively, inflammation contributes to injury or enhances CNS vulnerability. Acute inflammation can also be shifted to a chronic inflammatory state and/or adversely affect brain development. Hypothetically, microglia are the main immunocompetent cells in the immature CNS, and depending on the stimulus, molecular context, and timing, these cells will acquire various phenotypes, which will be critical regarding the CNS consequences of inflammation. Inflammation has long-term consequences and could speculatively modify the risk of a variety of neurological disorders, including cerebral palsy, autism spectrum disorders, schizophrenia, multiple sclerosis, cognitive impairment, and Parkinson disease. So far, the picture is incomplete, and data mostly experimental. Further studies are required to strengthen the associations in humans and to determine whether novel therapeutic interventions during the perinatal period can influence the occurrence of neurological disease later in life.

Evolutionary-developmental perspectives on immune system interactions among the pregnant woman, placenta, and fetus, and responses to sexually transmitted infectious agents

A balance has evolved over deep time between the various immune systems of the "triad" that is linked together for a short period: the pregnant woman, the fetus, and the placenta. This balance is affected by, and helps to determine, the immune responses to maternal infectious agents that may be transmitted to the fetus/infant transplacentally, intrapartum, or via breast milk. This review identifies newer evolutionary concepts and processes related particularly to the human placenta, innate and adaptive immune systems involved in tolerance, and in responses to sexually transmitted infectious (STI) agents that may be pathogenic to the fetus/infant at different gestational periods and in the first year of life. An evolutionary-developmental (EVO-DEVO) perspective has been applied to the complexities within, and among, the different actors and their beneficial or deleterious outcomes. Such a phylogenetic and ontogenic approach has helped to stimulate several basic questions and suggested possible explanations and novel practical interventions.

Nurr1 is not essential for the development of prepulse inhibition deficits induced by prenatal immune activation

Inflammation-induced disruption of fetal neurodevelopmental processes has been linked to the precipitation of long-lasting behavioral abnormalities and associated neuropathology. Recent longitudinal investigations in prenatal immune activation models have revealed developmental correspondences between the ontogeny of specific dopaminergic neuropathology and the postnatal onset of distinct forms of dopamine-dependent functional abnormalities implicated in schizophrenia. Two examples of such developmental correspondences are increased expression of the orphan nuclear receptor Nurr1 (NR4A2) in ventral midbrain areas and disruption of prepulse inhibition of the acoustic startle reflex, with both the neuroanatomical and behavioral effects emerging only in adult but not pre-pubertal subjects exposed to prenatal maternal inflammation. In the present study, we tested the hypothesis that Nurr1 may be a critical molecular mediator of prepulse inhibition deficits induced by prenatal immune activation. To this end, we compared the effects of prenatal immune challenge on adult PPI in wild-type (wt) mice and mice with a heterozygous constitutive deletion of Nurr1 (Nurr1+/-) using a well established mouse model of maternal immune activation by exposure to the viral mimetic poly(I:C) (=polyriboinosinic-polyribocytidilic acid). We found that prenatal poly(I:C) treatment on gestation day 9 was similarly effective in disrupting prepulse inhibition in adult wt and Nurr1+/- mice. Prenatal poly(I:C) treatment also generally increased midbrain Nurr1-positive cells and counteracted the genetically driven Nurr1 deficit in the substantia nigra. Our data thus suggest that at least under the present experimental conditions, Nurr1 is not essential for the development of prepulse inhibition deficits induced by prenatal immune activation.

Effects of antipsychotics on the behavioral deficits in human dominant-negative DISC1 transgenic mice with neonatal polyI:C treatment

Interactions of environmental and genetic factors may play a role in the pathoetiology of schizophrenia. We have recently developed a novel animal model of mental disorders such as schizophrenia by inducing abnormal immune response during the perinatal period in mice with overexpression of the human dominant-negative form of disrupted-in-schizophrenia 1 (DN-DISC1). In the present study, we investigated the effects of antipsychotics on the behavioral deficits in this animal model for mental disorders with gene-environment interaction. Neonatal DN-DISC1 transgenic (DN-DISC1 tg) mice were repeatedly injected with polyriboinosinic-polyribocytidylic acid (polyI:C) for 5 days from postnatal days 2 to 6. The behavioral analyses were performed in adulthood. Clozapine (3mg/kg) or haloperidol (1mg/kg) was administered orally once a day from 1 week before starting a series of behavioral experiments and continued until the end of the study. Cognitive impairment in polyI:C-treated DN-DISC1 tg mice was improved by repeated administration of clozapine while haloperidol had no effect. Both antipsychotics suppressed the augmentation of MK-801-induced hyperactivity in the model mice. Neither clozapine nor haloperidol ameliorated the impairments of social behaviors in polyI:C-treated DN-DISC1 tg mice. These results suggest that the polyI:C-treated DN-DISC tg mice are quite unique as an animal model for mental disorders. Furthermore, this mouse model may be useful for the screening of potential antipsychotic compounds that could be more effective than clozapine in ameliorating negative symptoms and cognitive impairment in schizophrenia.

Effect of paliperidone and risperidone on extracellular glutamate in the prefrontal cortex of rats exposed to prenatal immune activation or MK-801

The NMDA glutamate hypofunction model of schizophrenia is based in part upon acute effects of NMDA receptor blockade in humans and rodents. Several laboratories have reported glutamate system abnormalities following prenatal exposure to immune challenge, a known environmental risk factor for schizophrenia. Here we report indices of NMDA glutamate receptor hypofunction following prenatal immune activation, as well as the effects of treatment during periadolescence with the atypical antipsychotic medications risperidone and paliperidone. Pregnant Sprague-Dawley rats were injected with polyinosinic:polycytidylic acid (poly I:C) or saline on gestational day 14. Male offspring were treated orally via drinking water with vehicle, risperidone (0.01mg/kg/day), or paliperidone (0.01mg/kg/day) between postnatal days 35 and 56 (periadolescence) and extracellular glutamate levels in the prefrontal cortex were determined by microdialysis at PD 56. Consistent with decreased NMDA receptor function, MK-801-induced increases in extracellular glutamate concentration were markedly blunted following prenatal immune activation. Further suggesting NMDA receptor hypofunction, prefrontal cortex basal extracellular glutamate was significantly elevated (p<0.05) in offspring of poly I:C treated dams. Pretreatment with low dose paliperidone or risperidone (0.01mg/kg/day postnatal days 35-56) normalized prefrontal cortical basal extracellular glutamate (p<0.05 vs. poly I:C vehicle-treatment). Pretreatment with paliperidone and risperidone also prevented the acute MK-801-induced increase in extracellular glutamate. These observations demonstrate decreased NMDA receptor function and elevated extracellular glutamate, two key features of the NMDA glutamate receptor hypofunction model of schizophrenia, during periadolescence following prenatal immune activation. Treatment with the atypical antipsychotic medications paliperidone and risperidone normalized basal extracellular glutamate. Demonstration of glutamatergic abnormalities consistent with the NMDA glutamate receptor hypofunction model of schizophrenia as an early developmental consequence of prenatal immune action provides a model to identify novel early interventions targeting glutamatergic systems which play an important role in both positive and negative symptoms of schizophrenia.