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Maternal immune activation perturbs the brain epitranscriptome.

Maternal immune activation (MIA) results in abnormal fetal neurodevelopment and an increased risk of neurodevelopmental disorders. Altered RNA translation has been implicated in the pathophysiology of MIA-associated neurodevelopmental deficits, but more precise mechanisms underlying disruption in RNA metabolism are lacking. Here, we characterize key components of the RNA epitranscriptomic machinery, which refers to the set of reversible chemical modifications on RNA molecules that influence RNA function, including translation, stability, splicing, and localization. Using spatial transcriptomics, we define cell type- and brain region-specific distribution of epitranscriptome regulators in the developing mouse brain. We also use direct RNA sequencing to define how MIA changes the brain epitranscriptome landscape. We identify the demethylase FTO as being notably perturbed in the context of MIA. Using pharmacological and genetic approaches, we target FTO to ameliorate behavioral phenotypes in MIA offspring. In total, this work expands upon mechanisms of translational misregulation in MIA and identifies new targets for therapeutic manipulation.

Animals↗

Maternal Immune Activation Disrupts Epigenomic and Functional Maturation of Cortical Excitatory Neurons.

Elevated levels of maternal pro-inflammatory cytokines during gestation can disrupt offspring neural development, increasing the risk of neurodevelopmental disorders. We studied the effects of Poly(I:C)-induced maternal immune activation (PIC-MIA) during mid-gestation on developing cortical excitatory neurons' DNA methylation and transcriptome. PIC-MIA disrupted the developmental regulation of synapse-related genes and of genes implicated in autism spectrum disorders. Genomic regions that gain or lose DNA methylation during normal development were altered following PIC-MIA, including neurodevelopmental transcription factor binding sites. The DNA methylation and transcriptional changes were consistent with a delay in excitatory neuron maturation. Whole-cell recordings showed that PIC-MIA preferentially altered the physiological development of layer 5 excitatory neurons. Taken together, present results suggest that alterations in the epigenome, through the disruption of circuit formation, may drive the long-term consequences of maternal infection during gestation.

DNA methylation↗

Maternal immune activation disrupts epigenomic and functional maturation of cortical excitatory neurons.

Elevated levels of maternal pro-inflammatory cytokines following severe infection during gestation can disrupt offspring neural development and increase the risk of neurodevelopmental disorders. The viral mimetic Poly(I:C) reproduces the effects of gestational influenza exposure, leading to behavioral outcomes that recapitulate neurodevelopmental disorder phenotypes. Although Poly(I:C)-induced maternal immune activation (PIC-MIA) alters the epigenome, behavior and cognition of offspring in adulthood, it remains unclear when these changes occur and how MIA influences the epigenomic regulatory programming across the transition from embryonic development to the mature brain. Here, we examined the effects of PIC-MIA on the epigenomic maturation of the frontal cortex, focusing on excitatory neuron-specific DNA methylation and transcriptomic dynamics throughout perinatal development. Mid-gestation PIC-MIA disrupted development of the excitatory neuron transcriptome, with the largest alterations observed at birth. PIC-MIA altered the development of the mature DNA methylation program of excitatory neurons at thousands of genomic regulatory regions that normally gain or lose methylation during development. Transcription factor binding site analyses of these differentially methylated regions revealed a significant enrichment of Tbr1 motifs within hyper-methylated deep-layer neuron-specific regions at birth. Notably, transcriptional targets of Tbr1 were down-regulated at birth despite up-regulation of Tbr1 transcription, suggesting PIC-MIA uncouples Tbr1 expression from its regulatory function in deep-layer neurons. Electrophysiological recordings of intrinsic and firing properties further confirmed a lasting disruption in deep-layer neuronal activity. Our results suggest that mid-gestation MIA may alter the development of deep-layer neurons through an epigenomic blockade of Tbr1 function, thereby perturbing normal cortical circuit formation.

Journal Article↗

Maternal immune activation leads to behavioral and pharmacological changes in the adult offspring.

Maternal exposure to viral infection has been associated with an increased risk of schizophrenia in the offspring, and it has been suggested that the maternal immune response may interfere with normal fetal brain development. Although studies in rodents have shown that perinatal viral infections can lead to neuropathological and behavioral abnormalities considered relevant to schizophrenia, it is not clear whether these consequences are due to the infection itself or to the maternal immune response to infection. We show that an induction of maternal immune stimulation without exposure to a virus by injecting pregnant dams with the synthetic cytokine releaser polyriboinosinic-polyribocytidilic acid (poly I:C) leads to abnormal behavioral and pharmacological responses in the adult offspring. As in schizophrenia, these offspring displayed excessive behavioral switching, manifested in the loss of latent inhibition and in rapid reversal learning. Consistent with the clinical pharmacology of schizophrenia, both deficits were alleviated by antipsychotic treatment. In addition, these offspring displayed increased sensitivity to the locomotor-stimulating effects of MK-801, pointing to developmental alterations of the dopaminergic and/or glutamatergic systems. Prenatal poly I:C administration did not produce learning deficits in classical fear conditioning, active avoidance, discrimination learning and water maze. These results show that the maternal immune response is sufficient to cause behavioral and pharmacological alterations relevant to schizophrenia in the adult offspring.

Animals↗

Maternal immune activation during pregnancy increases limbic GABAA receptor immunoreactivity in the adult offspring: implications for schizophrenia.

Prenatal exposures to a variety of infections have been associated with an increased incidence of schizophrenia. We have reported that a single injection of the synthetic cytokine releaser PolyI:C to pregnant mice produced offspring that exhibited multiple schizophrenia-related behavioral deficits in adulthood. Here, we characterized the effect of maternal inflammation during fetal brain development on adult limbic morphology and expression of GABAA-receptors. The PolyI:C treatment did not induce morphological abnormalities but resulted in a significant increase in GABAA receptor subunit alpha2 immunoreactivity (IR) in the ventral dentate gyrus and basolateral amygdala in adult treated compared to control subjects. Correlative analyses between the a2 subunit IR in the ventral dentate gyrus and the performance in the prepulse inhibition paradigm revealed a significant correlation in controls that was however absent in the pathological condition. These results suggest that prenatal immune activation-induced disturbances of early brain development result in profound alterations in the limbic expression of GABAA receptors that may underlie the schizophrenia-related behavioral deficits in the adult mice.

Analysis of Variance↗

Nonspecific stimulation of the maternal immune system. I. Effects On teratogen-induced fetal malformations.

BACKGROUND: Maternal immune stimulation has reported, but unconfirmed, efficacy for reducing chemical-induced morphologic defects in mice. METHODS: Teratogenic chemicals (2,3,7, 8-tetrachlorodibenzo-p-dioxin [TCDD], ethyl carbamate [urethane], methylnitrosourea [MNU], or valproic acid [VA]) were given to pregnant mice to induce cleft palate (TCDD, urethane), digital defects (urethane, MNU), or exencephaly (VA). Before teratogen administration, the immune system of female mice was stimulated by intraperitoneal (IP) administration of pyran copolymer or attenuated bacillus Calmette Guérin (BCG), or by footpad injection with Freund's complete adjuvant (FCA). RESULTS: Fetal defects caused by all four chemicals studied were reduced by maternal immunostimulation, sometimes dramatically. In addition to reducing VA-induced exencephaly, immunostimulation with FCA resulted in fetal mice displaying anury (absence of tails). Activated maternal immune cells could not be detected in fetal circulation using flow cytometry and a fluorescent cell-tracking probe. CONCLUSIONS: For the chemicals tested, maternal immune stimulation has efficacy in reducing fetal defects. Immune protection against teratogenesis may be an indirect effect of maternal immune cell activation.

Abnormalities, Drug-Induced↗

[Resistance of mice with active and maternally passive immunity against Sendai virus].

Resistance of mice with active and maternally passive immunity to Sendai virus infection was investigated. Mice with active immunization were convalescent ones from intranasal infection with 10(3) TCID50 of the virus [CT], ones immunized with 4 weekly intranasal injections of about 4 X 10(3) hemagglutinating units (HAU) of formalin-inactivated virus (FV) [IN], or ones immunized with 4 weekly intraperitoneal injections of about 2 X 10(3) HAU of FV [IP]. The serum neutralizing (NT) antibody titers ranged 1 : 10 to 1 : 20 in CT and IN, and 1 : 20 to 1 : 40 in IP at 4 weeks after initial immunization. NT antibody in the lung lavage was detected only in IP in 3/5. After intranasal challenge infection with 10(6) TCID50 of the virus, little or no gross lung lesion, no virus recovery and no body weight loss were observed throughout experiment, in these 3 immunized groups, whereas, control mice showed lung lesions in 4/5 (7 days), virus recovery in 4/5 at 3 days and in 1/5 at 7 days post-challenge, and body weight loss. In additional histological study, bronchiolar epithelial methaplasia and alveolar septal thickening, which were characteristic findings in non-immunized infected mice, were not observed in mice immunized with 2 biweekly injection of about 250 HA of FV and then challenged. Maternal immunity was investigated in offsprings from convalescent dams infected with 10(3) TCID50 at mating [mCT] and from dams immunized intraperitoneally with 4 X 10(3) HAU of FV at 0, 1 and 2 weeks after mating and, 1 and 2 weeks after parturition [mIP]. Serum NT antibody was not detected in mCT, but the titers ranging 1 : 20 to 1 : 40 were detected in mIP. After intranasal challenge of mCT, mIP and offsprings from non-immune mice with 10(3) TCID50 of the virus, virus recovery on day 3 was 2/4, 1/4 and 3/3, and incidence of total lung lesions on day 7 and 12 was 11/21, 2/13 and 16/16, respectively. Body weight gain was suppressed slightly in the immune groups but markedly in the non-immune control.

Animals↗

Opposite effects of the maternal immune system activated by interleukin-1beta vs. PSK and OK432 on 5-azacytidine-induced birth defects.

Effects of stimulation of the maternal immune system on abnormal pregnancy induced with 5-azacytidine (5ACDR) administration at embryonic day 7.5 (E7.5) were examined in mice treated with recombinant interleukin 1beta (IL-1beta) at E6.5 (5ACDR + IL-1 at E6.5) or E9.5 (5ACDR + IL-1 at E9.5), OK432 (5ACDR + OK432) at E7.5 or PSK (5ACDR + PSK) at E7.5. Embryos from these dams were examined at E13.5. The frequency of dead and malformed embryos and number of malformations on each embryo increased in the 5ACDR + IL-1 at E6.5 groups compared with the 5ACDR-alone group. Adverse pregnancy outcomes in the 5ACDR + OK432 and 5ACDR + PSK groups were less frequent than in the 5ACDR-alone group. The frequency of exencephaly, facial cleft, eye anomalies (micro- or anophthalmos), and micrognathia significantly increased in the 5ACDR + IL-1 groups, in contrast, that of exencephaly decreased in the 5ACDR + OK432 and 5ACDR + PSK groups compared with the 5ACDR-alone group. The phagocytes on the exencephalic surface drastically increased in the 5ACDR + IL-1 groups, and they often appeared to ingest the migrating neuroepithelial cells. Such findings, however, were rarely observed in the 5ACDR-alone, 5ACDR + OK432 and 5ACDR + PSK groups. Thus, administration of IL-1beta to the abnormal pregnant dams increased the mortality and severity of the malformations in the embryos caused by 5ACDR, whereas PSK or OK432 decreased them. These results suggest that the different modes of activation of the maternal immune system may exert alternative or opposite effects on teratogenic pregnancy.

Abnormalities, Multiple↗

Apoptosis in the first trimester human placenta: the role in maintaining immune privilege at the maternal-foetal interface and in the trophoblast remodelling.

Apoptosis has been proposed as a mechanism for maintaining immune privilege. Expression of Fas ligand (FasL) by the human trophoblast has been recently accepted as a mechanism providing protection against the lytic action of activated decidual immune cells expressing Fas receptor (FasR). Therefore, the purpose of this review was to determine the role of apoptosis in early pregnancy maintenance according to the latest literature. We used Medline literature search. The data suggest that apoptosis may serve as a previously unsuspected mechanism that induces tolerance of the foetal allograft against maternal immune system. Apoptosis of activated maternal immune cells occurs in the human decidua mainly through Fas-FasL or receptor for TNF-related apoptosis-inducing ligand (TRAIL-R)-TNF-related apoptosis-inducing ligand (TRAIL) signalling. This might be a defence mechanism against rejection of the foetal allograft by the maternal immune system. In addition, in this review contribution of programmed cell death to placental cell turnover and remodelling during first trimester of pregnancy is also discussed.

Apoptosis↗

Influence of vaccine medium and vaccination schedules on the induction of active immunity against Aujeszky's disease in maternally immune pigs.

Active immunity against Aujeszky's disease virus (ADV) was compared at the end of the fattening period in pigs which had been vaccinated with the attenuated Bartha strain according to different schedules in the presence of different levels of maternal immunity. The percentage of seropositive pigs at the end of the fattening period varied from 21 to 94 per cent. The percentage was significantly higher when the vaccination schedules were applied to pigs from mothers vaccinated with an attenuated strain compared to pigs from mothers vaccinated with a subunit vaccine or from infected-immune mothers. Additionally, this percentage was two to three times lower when pigs were vaccinated once at 10 weeks old compared to pigs either revaccinated at 14 weeks or vaccinated once at 14 weeks old. When the virus strain used for vaccination had been suspended either in saline or in an oil-in-water emulsion, significant differences were not found in the serological response after vaccination and in the reduction of virus excretion upon subsequent challenge. In challenge experiments, a significantly longer duration of virus excretion was observed in vaccinated pigs which had not seroconverted than in vaccinated but seropositive pigs. The vaccination schedules for sows and fattening pigs in view of the eradication of ADV are discussed.

Animals↗

Investigating milk-derived extracellular vesicles as mediators of maternal stress and environmental intervention.

Parental communication signals are transmitted through nursing and critically shape neurodevelopmental trajectories. Mirroring some well characterized effects of gestational challenges in rodents, maternal immune activation (MIA) during the lactational period disrupts maternal physiology, decreases lipid content, and is associated with adverse neurobehavioral outcomes in offspring. This occurs without MIA significantly affecting maternal care. While gestational MIA models are responsive to environmental interventions, which beneficially alter maternal milk composition and associated offspring outcomes, the bioactive mediators in milk underlying resilience remain poorly understood. Milk-derived extracellular vesicles (MEVs) transport and deposit biologically active cargo, including microRNAs (miRNAs) that induce post-translational regulation of candidate mRNA in the nursing offspring's tissues and cells. Using a rat model, we show that lactational MIA alters MEV-miRNA cargo and the expression of hippocampal miRNAs in offspring. Several miRNAs in MEVs were also found in the hippocampus of matching offspring. Remarkably, the miRNA changes in MEVs and the neonatal hippocampus were rescued when dams were raised in an enriched environment, suggesting environmental enrichment protected from the effects of MIA. This was supported by the behavioral phenotype. RNA-seq of adult offspring hippocampus showed long-term transcriptional changes associated with the gene targets of early-life regulated miRNAs. Our results position MEV-miRNA as dynamic programming signals by which maternal experience is communicated to offspring, encoding both stress-induced and protective cues that influence development. This suggests that breastfeeding interventions can regulate the genetic cargo of the milk, programming the life of developing infants.

Journal Article↗

Possible interactions of genetic and immuno-neuro-endocrine regulatory mechanisms in pathogenesis of congenital anomalies.

The process of organogenesis depends on genetic and environmental factors. Besides genetic background, congenital anomalies can also be influenced by micro environmental changes, which are related to maternal-foetal interactions followed by the production of cytokines, hormones, neurotransmitters, growth factors and biochemical mediators, and stress proteins. Pre-natal maternal stress, including infections, psychological stress and other teratogens, can influence a disregulation of maternal immune, endocrine and nervous systems, during pregnancy. This is a crucial condition for the abnormal growth and development of the foetus. Activated maternal immune system can alter the cytokine network and make it inadequate for normal embryogenesis and organogenesis. Heat-shock proteins play an important role in stress physiology repairing DNA errors or activating pro-inflammatory response. Regarded from this aspect, the altered cytokine network suggests aetiopathogenetic basis of congenital anomalies in neonates. It is our wish to point out our potentially harmful conditions in the development of congenital anomalies, as well as their control by using pre-natal and pre-conceptional diagnostics and treatment.

Animals↗

Seminal 'priming' for protection from pre-eclampsia-a unifying hypothesis.

Conventional belief holds that an immune response to ejaculate antigens should interfere with fertilisation and establishment of pregnancy. However, emerging evidence now supports the opposing view-that insemination acts to activate maternal immune mechanisms exerting a positive effect on reproductive events. In a response well documented in rodents, semen triggers an influx of antigen-presenting cells into the female reproductive tract which process and present paternal ejaculate antigens to elicit activation of lymphocytes in the adaptive immune compartment. Transforming growth factor beta (TGFbeta), a cytokine present in abundance in seminal plasma, initiates this inflammatory response by stimulating the synthesis of pro-inflammatory cytokines and chemokines in uterine tissues. Lymphocyte activation is evident in lymph nodes draining the uterus and leads to hypo-responsiveness in T-cells reactive with paternal alloantigens. TGFbeta has potent immune-deviating effects and is likely to be the key agent in skewing the immune response against a Type-1 bias. Prior exposure to semen in the context of TGFbeta can be shown to be associated with enhanced fetal-placental development late in gestation. In this paper, we review the experimental basis for these claims and propose the hypothesis that, in women, the partner-specific protective effect of insemination in pre-eclampsia might be explained by induction of immunological hypo-responsiveness conferring tolerance to histocompatibility antigens present in the ejaculate and shared by the conceptus.

Animals↗

Effects of maternal infections on fetal adrenal steroid production.

We sought to determine the effect of maternal infections on the fetal hypothalamic-pituitary-adrenal axis. Umbilical cord blood was collected at vaginal delivery after labor (24-44 wk. gestation) from 361 infants of women having normal pregnancy ( apart from preterm delivery in some) and 110 infants of women diagnosed with infections: 86% of these women had amnionitis. Infants exposed to antenatal corticosteroids, being growth retarded, or having developmental abnormalities that would be expected to alter function of the hypothalamic-pituitary unit were excluded. Umbilical cord serum was assayed for dehydroepiandrosterone sulfate (DS) and for cortisol. The data were analyzed by use of SAS. The gestational age of the infants of normal women (35.8+/-0.2 wk., Mean +/- SE) was greater than that of the infants of women having infections (34.3+/-0.4 wk., P = 0.003). Umbilical cord serum levels of DS and cortisol rose as a function of gestational age in both groups of infants (P<0.01). Despite being, on average, 1 wk. younger than the normal infants are, the infants of women having infections during pregnancy had higher serum levels of cortisol and DS than did those infants of the normal women. These data are consistent with activation of the fetal hypothalamic-pituitary-adrenal axis in pregnancies complicated by maternal infections. Such a fetal response could be the consequence of transplacental passage of products of the activated maternal immune system.

Adrenal Cortex Hormones↗

Porphyromonas gingivalis infection during pregnancy increases maternal tumor necrosis factor alpha, suppresses maternal interleukin-10, and enhances fetal growth restriction and resorption in mice.

Epidemiological studies have shown a potential association between maternal periodontitis and pregnancy complications. We used a pregnant murine model to study the effect of infection with the periodontal pathogen Porphyromonas gingivalis on pregnancy outcomes. Female BALB/c mice were inoculated with heat-killed P. gingivalis (10(9) CFU) in a subcutaneous chamber and mated 2 weeks later. At gestation day (GD) 7.5, mice were challenged with live P. gingivalis (10(7) CFU) (n = 20) or broth (control; n = 8) and sacrificed at GD 16.5. Fetal growth restriction (FGR, <0.46 g) was defined as fetuses with weights 2 standard deviations (SD) smaller than controls (0.56 +/- 0.05 g [mean +/- SD]). Among the 20 challenged mice, 8 had both normal-weight (0.51 +/- 0.11 g) and FGR (0.34 +/- 0.1 g) fetuses within the same litter. All other challenged dams had normal-weight fetuses (0.57 +/- 0.04 g). Maternal liver, uterus, and spleen samples were examined for P. gingivalis DNA using a PCR technique. Of the eight challenged mice with FGR fetuses, three had PCR signals for P. gingivalis in liver and uterus, but not in the spleen. Liver, uterus, and spleen were negative for P. gingivalis DNA among all other challenged and control mice. In serum of dams with FGR fetuses, tumor necrosis factor alpha levels were elevated significantly, while interleukin-10 levels were significantly reduced compared to levels in dams with normal fetuses. P. gingivalis-specific serum immunoglobulin G levels were significantly elevated in dams with FGR fetuses compared to dams without any FGR fetuses. These data demonstrate that P. gingivalis-induced murine FGR is associated with systemic dissemination of the organism and activated maternal immune and inflammatory responses.

Animals↗

Orally administered microencapsulated reovirus can bypass suckled, neutralizing maternal antibody that inhibits active immunization of neonates.

Purified reovirus serotype 1, encapsulated in biodegradable aqueous microcapsules, was found to bypass maternal antibody passively transferred by suckling to neonates. Genetically identical, immunocompetent F1 scid/+ mice were generated by the reciprocal crosses of C.B17 scid/scid and normal congenic +/+ adult mice. The immunocompetent +/+ dams were either orally infected with reovirus prior to mating or not. Thus, these immunocompetent F1 pups developed either in the absence or in presence of passively transferred maternal immunity. The F1 mice were orally immunized on day 10 with either live virus, microencapsulated reovirus, or empty microcapsules plus live virus. The immune responses were assessed in the neonatal gut-associated lymphoid tissues (GALT). Examination of reovirus specific immunoglobulin A in the serum and GALT, taken on days 7, 14, and 21 postimmunization, clearly demonstrated that microencapsulated reovirus could bypass the normal effect of maternal antibodies, passively acquired by suckling, to inhibit active priming of neonates by oral route. These observations seem relevant to the development of efficacious oral vaccines that also allow passive, protective immunity via suckled maternal antibodies while permitting active oral immunization of neonates.

Administration, Oral↗