Maternal immune activation with staphylococcal enterotoxin A produces unique behavioral changes in C57BL/6 mouse offspring

Impact of Prenatal LPS and Early-life Constant Light Exposure on Circadian Gene Expression Profiles in Various Rat Tissues

Exposure to lipopolysaccharide (LPS) during prenatal development leads to various changes in neurobiological and behavioural patterns. Similarly, continuous exposure to constant light (LL) during the critical developmental period of the circadian system affects gene expression in various tissues in adulthood. Given the reciprocal nature of the interaction between the circadian and the immune systems, our study primarily investigated the individual effects of both interventions and, more importantly, their combined effect. We aimed to explore whether there might be a potential synergistic effect on circadian rhythms and their parameters, focussing on the expression of clock genes, immune-related genes, and specific genes in the hippocampus, pineal gland, spleen and adrenal gland of rats at postnatal day 30. Our results show a significant influence of prenatal LPS and postnatal LL on the expression profiles of all genes assessed. However, the combination of prenatal LPS and postnatal LL only revealed an enhanced negative effect in a minority of the comparisons. In most cases, it appeared to attenuate the changes induced by the individual interventions, restoring the measured parameters to values closer to those of the control group. In particular, genes such as Nr1d1, Aanat and Tph1 showed increased amplitude in the pineal gland and spleen, while the kynurenine enzymes Kynu and KatII developed circadian rhythmicity in the adrenal glands only after the combined interventions. Our data suggest that a mild immunological challenge during prenatal development may play a critical role in triggering an adaptive response of the circadian clock later in life.

Staphylococcal enterotoxin B exposed to pregnant rats inhibits the hedgehog signaling pathway in thymic T lymphocytes of the offspring

The Hedgehog (Hh) signaling pathway is involved in T cell differentiation and development and plays a major regulatory part in different stages of T cell development. A previous study by us suggested that prenatal exposure to staphylococcal enterotoxin B (SEB) changed the percentages of T cell subpopulation in the offspring thymus. However, it is unclear whether prenatal SEB exposure impacts the Hh signaling pathway in thymic T cells. In the present study, pregnant rats at gestational day 16 were intravenously injected once with 15 μg SEB, and the thymi of both neonatal and adult offspring rats were aseptically acquired to scrutinize the effects of SEB on the Hh signaling pathway. It firstly found that prenatal SEB exposure clearly caused the increased expression of Shh and Dhh ligands of the Hh signaling pathway in thymus tissue of both neonatal and adult offspring rats, but significantly decreased the expression levels of membrane receptors of Ptch1 and Smo, transcription factor Gli1, as well as target genes of CyclinD1, C-myc, and N-myc in Hh signaling pathway of thymic T cells. These data suggest that prenatal SEB exposure inhibits the Hh signaling pathway in thymic T lymphocytes of the neonatal offspring, and this effect can be maintained in adult offspring via the imprinting effect.

Mitochondrial bioenergetics stimulates autophagy for pathological tau clearance in tauopathy neurons

Hyperphosphorylation and aggregation of microtubule-associated tau is a pathogenic hallmark of tauopathies and a defining feature of Alzheimer's disease (AD). Pathological tau is targeted by autophagy for clearance, but autophagy dysfunction is indicated in tauopathy. While mitochondrial bioenergetic failure has been shown to precede the development of tau pathology, it is unclear whether energy metabolism deficiency is involved in tauopathy-related autophagy defects. Here, we reveal that stimulation of anaplerotic metabolism restores defective oxidative phosphorylation (OXPHOS) in tauopathy which, strikingly, leads to enhanced autophagy and pronounced tau clearance. OXPHOS-induced autophagy is attributed to increased ATP-dependent phosphatidylethanolamine biosynthesis in mitochondria. Excitingly, early bioenergetic stimulation boosts autophagy activity and reduces tau pathology, thereby counteracting memory impairment in tauopathy mice. Taken together, our study sheds light on a pivotal role of bioenergetic dysfunction in tauopathy-linked autophagy defects and suggests a new therapeutic strategy to prevent toxic tau buildup in AD and other tauopathies.

LPS-induced inflammation in rats during pregnancy reduces maternal melatonin and impairs neurochemistry and behavior of adult male offspring

Inflammation during pregnancy can induce neurodevelopmental changes that affect the neurological health of offspring. Elevated levels of circulating inflammatory cytokines have been shown to decrease nocturnal melatonin synthesis by the pineal gland, potentially impacting fetal development. This study aimed to assess the effects of LPS-induced inflammation on melatonin concentrations in the plasma of pregnant female rats and explore resulting neurochemical and behavioral changes in their offspring. Our findings revealed that pregnant rats injected with LPS experienced decreased nocturnal melatonin levels in their plasma, with an increase in diurnal melatonin content. The offspring exhibited reduced performance in tests evaluating motor coordination and spatial memory compared to control subjects. Immunohistochemical analysis indicated a decline in calbindin immunoreactivity in Purkinje cells in the cerebellum. Additionally, the hippocampus displayed an increase in IBA-1 and calretinin expression, coupled with a reduction in parvalbumin expression in the offspring of the LPS group. Collectively, this study provides compelling evidence that an inflammatory state can lead to a reduction in melatonin synthesis in pregnant females, potentially impacting the neurodevelopment of offspring, including neuronal, glial, motor, and cognitive aspects. Subsequent studies will further elucidate the mechanisms underlying inflammation-induced maternal melatonin reduction and its impact on offspring neurodevelopment.

Maternal pre-pregnancy obesity affects the uncinate fasciculus white matter tract in preterm infants

Background

A growing body of evidence suggests an association between a higher maternal pre-pregnancy body mass index (BMI) and adverse long-term neurodevelopmental outcomes for their offspring. Despite recent attention to the effects of maternal obesity on fetal and neonatal brain development, changes in the brain microstructure of preterm infants born to mothers with pre-pregnancy obesity are still not well understood. This study aimed to detect the changes in the brain microstructure of obese mothers in pre-pregnancy and their offspring born as preterm infants using diffusion tensor imaging (DTI).

Methods

A total of 32 preterm infants (born to 16 mothers with normal BMI and 16 mothers with a high BMI) at <32 weeks of gestation without brain injury underwent brain magnetic resonance imaging at term-equivalent age (TEA). The BMI of all pregnant women was measured within approximately 12 weeks before pregnancy or the first 2 weeks of gestation. We analyzed the brain volume using a morphologically adaptive neonatal tissue segmentation toolbox and calculated the major white matter (WM) tracts using probabilistic maps of the Johns Hopkins University neonatal atlas. We investigated the differences in brain volume and WM microstructure between preterm infants of mothers with normal and high BMI. The DTI parameters were compared among groups using analysis of covariance adjusted for postmenstrual age at scan and multiple comparisons.

Results

Preterm infants born to mothers with a high BMI showed significantly increased cortical gray matter volume (p = 0.001) and decreased WM volume (p = 0.003) after controlling for postmenstrual age and multiple comparisons. We found a significantly lower axial diffusivity in the uncinate fasciculus (UNC) in mothers with high BMI than that in mothers with normal BMI (1.690 ± 0.066 vs. 1.762 ± 0.101, respectively; p = 0.005).

Conclusion

Our study is the first to demonstrate that maternal obesity impacts perinatal brain development patterns in preterm infants at TEA, even in the absence of apparent brain injury. These findings provide evidence for the detrimental effects of maternal obesity on brain developmental trajectories in offspring and suggest potential neurodevelopmental outcomes based on an altered UNC WM microstructure, which is known to be critical for language and social-emotional functions.

Enterotoxins A and B produced by Staphylococcus aureus increase cell proliferation, invasion and cytarabine resistance in acute myeloid leukemia cell lines

As in the case of cancer, the risk of infection increases when the host's immune system is not working properly. It has been shown that toxins produced by the bacteria responsible for bacterial infections can alter the properties of cancer cells as well as their sensitivity to chemotherapy agents. Staphylococcus aureus (S. aureus) is one of the most prevalent pathogens in acute myeloid leukemia (AML) patients and it produces several virulence factors, including Staphylococcal enterotoxin A (SEA) and Staphylococcal enterotoxin B (SEB). Cytotoxicity, transwell migration, invasion assays, and various transcriptomic and gene set enrichment (GSE) analyses were used to determine how SEA and SEB alter cell proliferation, migration, invasion, and Cytarabine (Cyt) resistance in AML cell lines. The treatment of AML cell lines with SEA/SEB caused an increase in cell proliferation and Cyt resistance. Toxins enhanced the proclivity of cells to migrate and invade, with around 50% of cells in the presence of SEA and SEB. Transcriptomic and gene set enrichment analyses, and subsequent PCR validations showed dysregulation of immune related genes and genesets. Apparently, this allows AML cells to escape and survive the undesirable environment created by toxins, possibly via the ER stress signaling pathway. Therefore, SEA and SEB can significantly alter the characteristics of AML cancer cells and evaluation of alterations in responsible immune genes and pathways may be crucial for controlling the progression of cancer. In addition, our results suggest that there may be a strong interaction between the immune related pathways and the ER signaling pathway.

Interaction of the pre- and postnatal environment in the maternal immune activation model

Adverse influences during pregnancy are associated with a range of unfavorable outcomes for the developing offspring. Maternal psychosocial stress, exposure to infections and nutritional imbalances are known risk factors for neurodevelopmental derangements and according psychiatric and neurological manifestations later in offspring life. In this context, the maternal immune activation (MIA) model has been extensively used in preclinical research to study how stimulation of the maternal immune system during gestation derails the tightly coordinated sequence of fetal neurodevelopment. The ensuing consequence of MIA for offspring brain structure and function are majorly manifested in behavioral and cognitive abnormalities, phenotypically presenting during the periods of adolescence and adulthood. These observations have been interpreted within the framework of the "double-hit-hypothesis" suggesting that an elevated risk for neurodevelopmental disorders results from an individual being subjected to two adverse environmental influences at distinct periods of life, jointly leading to the emergence of pathology. The early postnatal period, during which the caregiving parent is the major determinant of the newborn´s environment, constitutes a window of vulnerability to external stimuli. Considering that MIA not only affects the developing fetus, but also impinges on the mother´s brain, which is in a state of heightened malleability during pregnancy, the impact of MIA on maternal brain function and behavior postpartum may importantly contribute to the detrimental consequences for her progeny. Here we review current information on the interaction between the prenatal and postnatal maternal environments in the modulation of offspring development and their relevance for the pathophysiology of the MIA model.

Cohort-guided insights into gene-environment interactions in autism spectrum disorders

Prospective birth cohorts offer unprecedented opportunities to investigate the pathogenesis of complex disorders such as autism, in which gene-environment interactions must be appreciated in a temporal context. This Perspective article considers the history of autism research, including missteps that reflected an incomplete understanding of the epidemiology of autistic spectrum disorders, the effects of advocacy and philanthropy on the trajectory of scientific inquiry, and the current and future roles of prospective birth cohort research in illuminating the pathology of these and other complex disorders wherein exposures during gestation might not manifest until later in life.

Intrauterine Inflammation Leads to Select Sex- and Age-Specific Behavior and Molecular Differences in Mice

Sex-specific differences in behavior have been observed in anxiety and learning in children exposed to prenatal inflammation; however, whether these behaviors manifest differently by age is unknown. This study assesses possible behavioral changes due to in utero inflammation as a function of age in neonatal, juvenile, and adult animals and presents potential molecular targets for observed differences. CD-1 timed pregnant dams were injected in utero with lipopolysaccharide (LPS, 50 μg/animal) or saline at embryonic day 15. No differences in stress responses were measured by neonatal ultrasonic vocalizations between LPS- and saline-exposed groups of either sex. By contrast, prenatal inflammation caused a male-specific increase in anxiety in mature but not juvenile animals. Juvenile LPS-exposed females had decreased movement in open field testing that was not present in adult animals. We additionally observed improved memory retrieval after in utero LPS in the juvenile animals of both sexes, which in males may be related to a perseverative phenotype. However, there was an impairment of long-term memory in only adult LPS-exposed females. Finally, gene expression analyses revealed that LPS induced sex-specific changes in genes involved in hippocampal neurogenesis. In conclusion, intrauterine inflammation has age- and sex-specific effects on anxiety and learning that may correlate to sex-specific disruption of gene expression associated with neurogenesis in the hippocampus.

Sources and Translational Relevance of Heterogeneity in Maternal Immune Activation Models

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

Impact of Gestational Haloperidol Exposure on miR-137-3p and Nr3c1 mRNA Expression in Hippocampus of Offspring Mice

BACKGROUND

Schizophrenia is a mental disorder caused by both environmental and genetic factors. Prenatal exposure to antipsychotics, an environmental factor for the fetal brain, induces apoptotic neurodegeneration and cognitive impairment of offspring similar to schizophrenia. The aim was to investigate molecular biological changes in the fetal hippocampus exposed to haloperidol (HAL) by RNA expression as a model of the disorder.

METHODS

HAL (1 mg/kg/d) was administered to pregnant mice. Upregulated and downregulated gene expressions in the hippocampus of offspring were studied with RNA-sequencing and validated with the qPCR method, and micro-RNA (miR) regulating mRNA expressional changes was predicted by in silico analysis. An in vitro experiment was used to identify the miRNA using a dual-luciferase assay.

RESULTS

There were significant gene expressional changes (1370 upregulated and 1260 downregulated genes) in the HAL group compared with the control group on RNA-sequencing analysis (P &lt; .05 and q &lt; 0.05). Of them, the increase of Nr3c1 mRNA expression was successfully validated, and in silico analysis predicted that microRNA-137-3p (miR-137-3p) possibly regulates that gene's expression. The expression of miR-137-3p in the hippocampus of offspring was significantly decreased in the first generation, but it increased in the second generation. In vitro experiments with Neuro2a cells showed that miR-137-3p inversely regulated Nr3c1 mRNA expression, which was upregulated in the HAL group.

CONCLUSIONS

These findings will be key for understanding the impact of the molecular biological effects of antipsychotics on the fetal brain.

Resveratrol Prevents Cytoarchitectural and Interneuronal Alterations in the Valproic Acid Rat Model of Autism

Autism spectrum disorder (ASD) is a prevalent neurodevelopmental disorder characterized by several alterations, including disorganized brain cytoarchitecture and excitatory/inhibitory (E/I) imbalance. We aimed to analyze aspects associated with the inhibitory components in ASD, using bioinformatics to develop notions about embryonic life and tissue analysis for postnatal life. We analyzed microarray and RNAseq datasets of embryos from different ASD models, demonstrating that regions involved in neuronal development are affected. We evaluated the effect of prenatal treatment with resveratrol (RSV) on the neuronal organization and quantity of parvalbumin-positive (PV+), somatostatin-positive (SOM+), and calbindin-positive (CB+) GABAergic interneurons, besides the levels of synaptic proteins and GABA receptors in the medial prefrontal cortex (mPFC) and hippocampus (HC) of the ASD model induced by valproic acid (VPA). VPA increased the total number of neurons in the mPFC, while it reduced the number of SOM+ neurons, as well as the proportion of SOM+, PV+, and CB+ neurons (subregion-specific manner), with preventive effects of RSV. In summary, metabolic alterations or gene expression impairments could be induced by VPA, leading to extensive damage in the late developmental stages. By contrast, due to its antioxidant, neuroprotective, and opposite action on histone properties, RSV may avoid damages induced by VPA.

Modestly increasing systemic interleukin-6 perinatally disturbs secondary germinal zone neurogenesis and gliogenesis and produces sociability deficits

Epidemiologic studies have demonstrated that infections during pregnancy increase the risk of offspring developing Schizophrenia, Autism, Depression and Bipolar Disorder and have implicated interleukin-6 (IL-6) as a causal agent. However, other cytokines have been associated with the developmental origins of psychiatric disorders; therefore, it remains to be established whether elevating IL-6 is sufficient to alter the trajectory of neural development. Furthermore, most rodent studies have manipulated the maternal immune system at mid-gestation, which affects the stem cells and progenitors in both the primary and secondary germinal matrices. Therefore, a question that remains to be addressed is whether elevating IL-6 when the secondary germinal matrices are most active will affect brain development. Here, we have increased IL-6 from postnatal days 3-6 when the secondary germinal matrices are rapidly expanding. Using Nestin-Cre^ERT2 fate mapping we show that this transient increase in IL-6 decreased neurogenesis in the dentate gyrus of the dorsal hippocampus, reduced astrogliogenesis in the amygdala and decreased oligodendrogenesis in the body and splenium of the corpus callosum all by ∼ 50%. Moreover, the IL-6 treatment elicited behavioral changes classically associated with neurodevelopmental disorders. As adults, IL-6 injected male mice lost social preference in the social approach test, spent ∼ 30% less time socially engaging with sexually receptive females and produced ∼ 50% fewer ultrasonic vocalizations during mating. They also engaged ∼ 50% more time in self-grooming behavior and had an increase in inhibitory avoidance. Altogether, these data provide new insights into the biological mechanisms linking perinatal immune activation to complex neurodevelopmental brain disorders.

Maternal inflammation and its ramifications on fetal neurodevelopment

Exposure to heightened inflammation in pregnancy caused by infections or other inflammatory insults has been associated with the onset of neurodevelopmental and psychiatric disorders in children. Rodent models have provided unique insights into how this maternal immune activation (MIA) disrupts brain development. Here, we discuss the key immune factors involved, highlight recent advances in determining the molecular and cellular pathways of MIA, and review how the maternal immune system affects fetal development. We also examine the roles of microbiomes in shaping maternal immune function and the development of autism-like phenotypes. A comprehensive understanding of the gut bacteria-immune-neuro interaction in MIA is essential for developing diagnostic and therapeutic measures for high-risk pregnant women and identifying targets for treating inflammation-induced neurodevelopmental disorders.

Broad activation of the Parkin pathway induces synaptic mitochondrial deficits in early tauopathy

Mitochondrial defects are a hallmark of early pathophysiology in Alzheimer's disease, with pathologically phosphorylated tau reported to induce mitochondrial toxicity. Mitophagy constitutes a key pathway in mitochondrial quality control by which damaged mitochondria are targeted for autophagy. However, few details are known regarding the intersection of mitophagy and pathologies in tauopathy. Here, by applying biochemical and cell biological approaches including time-lapse confocal imaging in live tauopathy neurons, combined with gene rescue experiments via stereotactic injections of adeno-associated virus particles into tauopathy mouse brains, electrophysiological recordings and behavioural tests, we demonstrate for the first time that mitochondrial distribution deficits at presynaptic terminals are an early pathological feature in tauopathy brains. Furthermore, Parkin-mediated mitophagy is extensively activated in tauopathy neurons, which accelerates mitochondrial Rho GTPase 1 (Miro1) turnover and consequently halts Miro1-mediated mitochondrial anterograde movement towards synaptic terminals. As a result, mitochondrial supply at tauopathy synapses is disrupted, impairing synaptic function. Strikingly, increasing Miro1 levels restores the synaptic mitochondrial population by enhancing mitochondrial anterograde movement and thus reverses tauopathy-associated synaptic failure. In tauopathy mouse brains, overexpression of Miro1 markedly elevates synaptic distribution of mitochondria and protects against synaptic damage and neurodegeneration, thereby counteracting impairments in learning and memory as well as synaptic plasticity. Taken together, our study reveals that activation of the Parkin pathway triggers an unexpected effect-depletion of mitochondria from synaptic terminals, a characteristic feature of early tauopathy. We further provide new mechanistic insights into how parkin activation-enhanced Miro1 degradation and impaired mitochondrial anterograde transport drive tauopathy-linked synaptic pathogenesis and establish a foundation for future investigations into new therapeutic strategies to prevent synaptic deterioration in Alzheimer's disease and other tauopathies.

Hypothalamic melanin-concentrating hormone regulates hippocampus-dorsolateral septum activity

Hypothalamic melanin-concentrating hormone (MCH) polypeptide contributes to regulating energy homeostasis, sleep, and memory, though the mechanistic bases of its effects are unknown. Here, in mice, we uncover the physiological mechanism underlying the functional role of MCH signaling in projections to the dorsolateral septum (dLS), a region involved in routing hippocampal firing rhythms and encoding spatial memory based on such rhythms. Firing activity within the dLS in response to dorsal CA3 (dCA3) excitation is limited by strong feed-forward inhibition (FFI). We find that MCH synchronizes dLS neuronal firing with its dCA3 inputs by enhancing GABA release, which subsequently reduces the FFI and augments dCA3 excitatory input strength, both via presynaptic mechanisms. At the functional level, our data reveal a role for MCH signaling in the dLS in facilitating spatial memory. These findings support a model in which peptidergic signaling within the dLS modulates dorsal hippocampal output and supports memory encoding.

Influence of Prenatal Drug Exposure, Maternal Inflammation, and Parental Aging on the Development of Autism Spectrum Disorder

Autism spectrum disorder (ASD) affects reciprocal social interaction and produces abnormal repetitive, restrictive behaviors and interests. The diverse causes of ASD are divided into genetic alterations and environmental risks. The prevalence of ASD has been rising for several decades, which might be related to environmental risks as it is difficult to consider that the prevalence of genetic disorders related to ASD would increase suddenly. The latter includes (1) exposure to medications, such as valproic acid (VPA) and selective serotonin reuptake inhibitors (SSRIs) (2), maternal complications during pregnancy, including infection and hypertensive disorders of pregnancy, and (3) high parental age. Epidemiological studies have indicated a pathogenetic role of prenatal exposure to VPA and maternal inflammation in the development of ASD. VPA is considered to exert its deleterious effects on the fetal brain through several distinct mechanisms, such as alterations of γ-aminobutyric acid signaling, the inhibition of histone deacetylase, the disruption of folic acid metabolism, and the activation of mammalian target of rapamycin. Maternal inflammation that is caused by different stimuli converges on a higher load of proinflammatory cytokines in the fetal brain. Rodent models of maternal exposure to SSRIs generate ASD-like behavior in offspring, but clinical correlations with these preclinical findings are inconclusive. Hypertensive disorders of pregnancy and advanced parental age increase the risk of ASD in humans, but the mechanisms have been poorly investigated in animal models. Evidence of the mechanisms by which environmental factors are related to ASD is discussed, which may contribute to the development of preventive and therapeutic interventions for ASD.

Maternal COVID-19 Vaccination and Its Potential Impact on Fetal and Neonatal Development

Vaccines have been developed at "warp speed" to combat the COVID-19 pandemic caused by the SARS-CoV-2 coronavirus. Although they are considered the best approach for preventing mortality, when assessing the safety of these vaccines, pregnant women have not been included in clinical trials. Thus, vaccine safety for this demographic, as well as for the developing fetus and neonate, remains to be determined. A global effort has been underway to encourage pregnant women to get vaccinated despite the uncertain risk posed to them and their offspring. Given this, post-hoc data collection, potentially for years, will be required to determine the outcomes of COVID-19 and vaccination on the next generation. Most COVID-19 vaccine reactions include injection site erythema, pain, swelling, fatigue, headache, fever and lymphadenopathy, which may be sufficient to affect fetal/neonatal development. In this review, we have explored components of the first-generation viral vector and mRNA COVID-19 vaccines that are believed to contribute to adverse reactions and which may negatively impact fetal and neonatal development. We have followed this with a discussion of the potential for using an ovine model to explore the long-term outcomes of COVID-19 vaccination during the prenatal and neonatal periods.

Mycobacterium tuberculosis causes a leaky blood-brain barrier and neuroinflammation in the prefrontal cortex and cerebellum regions of infected mice offspring

The maternal system's exposure to pathogens influences foetal brain development through the influx of maternal cytokines and activation of the foetal immune status to a persistent inflammatory state characterised by glia cell activation. Neuroinflammation influences the blood-brain barrier's (BBB) permeability allowing peripheral immune cell trafficking into the brain. Mycobacterium tuberculosis (Mtb) is a pathogen that causes Tuberculosis (TB), a global pandemic responsible for health and economic burdens. Although it is known that maternal infections increase the risk of Autism spectrum disorder (ASD), it is not known whether gestational Mtb infections also contribute to impaired foetal neurodevelopment. Here we infect pregnant Balb/c mice with Mtb H37Rv and Valproic acid (VPA) individually and in combination. Neuroinflammation was measured by assessing microglia and astrocyte population in the prefrontal cortex (PFC) and cerebellum (CER) of pups. Mtb infection increased the microglia population and caused morphological changes to a reactive phenotype in the PFC. Also, the astrocyte population was significantly increased in the PFC of Mtb pups. The BBB permeability was determined by measuring the Evans Blue (EB) dye concentration in the PFC and CER 1 hr post receiving intravenous EB-dye injection. We found that prenatal Mtb exposure significantly increased the BBB's permeability in the PFC and CER of pups versus saline. Overall, our data demonstrate that prenatal exposure to Mtb predisposes offspring to a higher risk of BBB damage while inducing persistent neuroinflammation, which could lead to impaired neuronal development and function. These findings implicate a potential role of gestational Mtb infections in the aetiology of ASD.

Maternal obesity and developmental programming of neuropsychiatric disorders: An inflammatory hypothesis

Maternal obesity is associated with the development of a variety of neuropsychiatric disorders; however, the mechanisms behind this association are not fully understood. Comparison between maternal immune activation and maternal obesity reveals similarities in associated impairments and maternal cytokine profile. Here, we present a summary of recent evidence describing how inflammatory processes contribute towards the development of neuropsychiatric disorders in the offspring of obese mothers. This includes discussion on how maternal cytokine levels, fatty acids and placental inflammation may interact with foetal neurodevelopment through changes to microglial behaviour and epigenetic modification. We also propose an exosome-mediated mechanism for the disruption of brain development under maternal obesity and discuss potential intervention strategies.

Potential role of primed microglia during obesity on the mesocorticolimbic circuit in autism spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disease which involves functional and structural defects in selective central nervous system (CNS) regions that harm function and individual ability to process and respond to external stimuli. Individuals with ASD spend less time engaging in social interaction compared to non-affected subjects. Studies employing structural and functional magnetic resonance imaging reported morphological and functional abnormalities in the connectivity of the mesocorticolimbic reward pathway between the nucleus accumbens and the ventral tegmental area (VTA) in response to social stimuli, as well as diminished medial prefrontal cortex in response to visual cues, whereas stronger reward system responses for the non-social realm (e.g., video games) than social rewards (e.g., approval), associated with caudate nucleus responsiveness in ASD children. Defects in the mesocorticolimbic reward pathway have been modulated in transgenic murine models using D2 dopamine receptor heterozygous (D2+/-) or dopamine transporter knockout mice, which exhibit sociability deficits and repetitive behaviors observed in ASD phenotypes. Notably, the mesocorticolimbic reward pathway is modulated by systemic and central inflammation, such as primed microglia, which occurs during obesity or maternal overnutrition. Therefore, we propose that a positive energy balance during obesity/maternal overnutrition coordinates a systemic and central inflammatory crosstalk that modulates the dopaminergic neurotransmission in selective brain areas of the mesocorticolimbic reward pathway. Here, we will describe how obesity/maternal overnutrition may prime microglia, causing abnormalities in dopamine neurotransmission of the mesocorticolimbic reward pathway, postulating a possible immune role in the development of ASD.

Maternal Immunity in Autism Spectrum Disorders: Questions of Causality, Validity, and Specificity

Autism spectrum disorders (ASD) are complex neurodevelopmental disorders with unknown heterogeneous aetiologies. Epidemiological studies have found an association between maternal infection and development of ASD in the offspring, and clinical findings reveal a state of immune dysregulation in the pre- and postnatal period of affected subjects. Maternal immune activation (MIA) has been proposed to mediate this association by altering fetal neurodevelopment and leading to autism. Although animal models have supported a causal link between MIA and development of ASD, their validity needs to be explored. Moreover, considering that only a small proportion of affected offspring develop autism, and that MIA has been implicated in related diseases such as schizophrenia, a key unsolved question is how disease specificity and phenotypic outcome are determined. Here, we have integrated preclinical and clinical evidence, including the use of animal models for establishing causality, to explore the role of maternal infections in ASD. A proposed priming/multi-hit model may offer insights into the clinical heterogeneity of ASD, its convergence with related disorders, and therapeutic strategies.

Maternal Immune Activation Induces Neuroinflammation and Cortical Synaptic Deficits in the Adolescent Rat Offspring

Maternal immune activation (MIA), induced by infection during pregnancy, is an important risk factor for neuro-developmental disorders, such as autism. Abnormal maternal cytokine signaling may affect fetal brain development and contribute to neurobiological and behavioral changes in the offspring. Here, we examined the effect of lipopolysaccharide-induced MIA on neuro-inflammatory changes, as well as synaptic morphology and key synaptic protein level in cerebral cortex of adolescent male rat offspring. Adolescent MIA offspring showed elevated blood cytokine levels, microglial activation, increased pro-inflammatory cytokines expression and increased oxidative stress in the cerebral cortex. Moreover, pathological changes in synaptic ultrastructure of MIA offspring was detected, along with presynaptic protein deficits and down-regulation of postsynaptic scaffolding proteins. Consequently, ability to unveil MIA-induced long-term alterations in synapses structure and protein level may have consequences on postnatal behavioral changes, associated with, and predisposed to, the development of neuropsychiatric disorders.

Exposure of pregnant rats to staphylococcal enterotoxin B attenuates the response of increased Tregs to re-exposure to SEB in the thymus of adult offspring

Regulatory T cells (Tregs) play an essential role during homeostasis and tolerance of the immune system. Based on our previous study that exposure of pregnant rats to staphylococcal enterotoxin B (SEB) can alter the percentage of CD4/CD8 subsets in the thymus of the offspring, in this study, we focus on the influence of exposure of pregnant rats to SEB on number, function and response of Tregs in the thymus of the offspring. Pregnant rats at gestational day of 16 were intravenously injected with 15 μg SEB and the thymuses of the neonatal and adult offspring were harvested for this study. We found that exposure of pregnant rats to SEB could significantly increase the absolute number of Tregs and the FoxP3 expression level in the thymus of not only neonatal but also adult offspring. Re-exposure of adult offspring to SEB remarkably reduced the suppressive capacity of Tregs to CD4⁺ T cells and the expression levels of TGF-β and IL-10 in the thymus, but had no effect on production of IL-4 and IFN-γ. Furthermore, it also notedly decreased the absolute number of Tregs and the FoxP3 expression level. These data suggest that prenatal exposure of pregnant rats to SEB attenuates the response of increased Tregs to re-exposure to SEB in the thymus of adult offspring.

Lipopolysaccharide exposure during late embryogenesis triggers and drives Alzheimer-like behavioral and neuropathological changes in CD-1 mice

INTRODUCTION

Infections could contribute to Alzheimer's disease (AD) neuropathology in human. However, experimental evidence for a causal relationship between infections during the prenatal phase and the onset of AD is lacking.

METHODS

CD-1 mothers were intraperitoneally received lipopolysaccharide (LPS) with two doses (25 and 50 μg/kg) or normal saline every day during gestational days 15-17. A battery of behavioral tasks was used to assess the species-typical behavior, sensorimotor capacity, anxiety, locomotor activity, recognition memory, and spatial learning and memory in 1-, 6-, 12-, 18-, and 22-month-old offspring mice. An immunohistochemical technology was performed to detect neuropathological indicators consisting of amyloid-β (Aβ), phosphorylated tau (p-tau), and glial fibrillary acidic protein (GFAP) in the hippocampus.

RESULTS

Compared to the same-aged controls, LPS-treated offspring had similar behavioral abilities and the levels of Aβ42, p-tau, and GFAP at 1 and 6 months old. From 12 months onward, LPS-treated offspring gradually showed decreased species-typical behavior, sensorimotor ability, locomotor activity, recognition memory, and spatial learning and memory, and increased anxieties and the levels of Aβ42, p-tau, and GFAP relative to the same-aged controls. Moreover, this damage effect (especially cognitive decline) persistently progressed onwards. The changes in these neuropathological indicators significantly correlated with impaired spatial learning and memory.

CONCLUSIONS

Prenatal exposure to low doses of LPS caused AD-related features including behavioral and neuropathological changes from midlife to senectitude.

Adult conditional knockout of PGC-1α in GABAergic neurons causes exaggerated startle reactivity, impaired short-term habituation and hyperactivity

Interneurons not only contribute to the global balance of activity in cortical networks but also mediate the precise gating of information through specific proteins. Accumulating evidence demonstrates that peroxisome-proliferator-activated receptor-gamma co-activator 1 alpha (PGC-1α) is concentrated in inhibitory interneurons and that it plays an important role in neuropsychiatric diseases. However, the functions of the transcriptional coactivator PGC-1α in sensorimotor gating, short-term habituation and spatial reference memory are still not entirely clear. To investigate the precise involvement of PGC-1α in the progression of psychiatric disorders, we first generated PGC-1α conditional knockout mice through transgenic expression of Cre recombinase under the control of dlx5/6 promoter, Cre-mediated excision events occurred specifically in γ-amino-butyric-acid-(GABA)ergic neurons. Short-term habituation and spatial reference memory in Dlx5/6-Cre::PGC-1α^fl/fl mice were evaluated using the novel object recognition test and the Morris water maze test, and sensorimotor gating was measured by prepulse inhibition of the acoustic startle reflex. Protein expression of parvalbumin (PV) in specific brain regions was studied by western blotting, immunofluorescence and immunohistochemistry. Here, we show that mice lacking the PGC-1α gene in GABAergic neurons exhibit deficits in short-term habituation, hyperactivity, reduced prepulse inhibition and exaggerated startle reactivity but normal associative spatial reference memory. In particular, these mice display aberrant salience, whereby more attention is paid to a further copy of the original object (now familiar) (relative to the first presentation of the original object, and relative to the presentation of the novel object). These behavioral dysfunctions were associated with decreased PV expression in the cortex (including somatosensory and motor cortex) as well as in the hippocampus, especially in its CA1 and CA3 regions. Together, these findings draw attention to a hyper-response phenotype of PGC-1α conditional knockout mice and indicate that PGC-1α is a novel regulator of gene expression and function in PV-positive interneurons and a potential therapeutic target for psychiatric disorders associated with PGC-1α dysregulation.

Atypical antipsychotic drug modulates early life infection induced impairment of hypothalamic-pituitary-adrenal axis: An age related study in mice

Evidences from human and animal studies indicate that exposure to infection during early life act as a stressor to impair the hypothalamic-pituitary-adrenal (HPA) axis and may be one of the contributing factors of mental illness of later life. Several atypical antipsychotic drugs (AAPDs) proved to be effective in alleviating psychiatric illness through normalization of HPA axis. However, AAPD are least tried to evaluate their efficacy in modulation of HPA axis impaired under infection. The present study elucidated that the treatment with AAPD paliperidone (PAL: 0.025 mg/kg/bw and 0.05 mg/kg/bw) during periadolescence period (postnatal day 35- postnatal day 56) dose-dependently normalized the HPA axis of the female mice who were gestationally (gestational day 15 and 17) exposed to bacterial endotoxin lipopolysaccharide (LPS: 800 μg/kg/bw; intraperitoneally). The effectiveness of PAL treatment in counteracting the LPS induced hyperactivity of HPA axis was age-related, better observed at postnatal day 120 than at postnatal day 200. The PAL modulation of HPA axis reflected at different levels: inhibition of hypothalamic CRF expression and reduction in plasma levels of adrenocorticotropin and corticosterone. Histopathological alterations such as hypertrophy and/or hyperplasia in cortical zona fasciculata as well as medullary chromaffin cells of adrenal also normalized on PAL treatment. The comparatively long wash out period after drug treatment (postnatal day 57- postnatal day 200) along with age related hormonal imbalance could be correlated to less effectiveness of PAL on HPA axis at postnatal day 200. PAL modulation of HPA axis might be through maintenance of cytokines and reproductive axis homeostasis.

Inflammatory domains modulate autism spectrum disorder susceptibility during maternal nutritional programming

Autism spectrum disorder (ASD) is a complex neurodevelopmental disease which involves functional and structural defects in selective central nervous system (CNS) regions harming capability to process and respond to external stimuli. In addition to genetic background, etiological causes of ASD have not been fully clarified. Maternal immune activation (MIA) during pregnancy have been proposed as a potential etiological cause leading to aberrant synaptic pruning and microglia-mediated neurogenesis impairment. Several clinical studies suggest that pro-inflammatory profile during maternal obesity associates with a higher risk of having a child with autism. In this context, the effect of maternal programing by high fat diet overconsumption during pregnancy sets a pro-inflammatory profile partly dependent on an epigenetic program of immunity which promotes brain micro and macrostructural abnormalities in the offspring that might last through adulthood accompanied by phenotypic changes in ASD subjects. Of note, maternal programming of inflammation during development seems to integrate the CNS and peripheral immune system cross-talk which arrays central inflammatory domains coordinating ASD behavior. In this review, we discuss basic and clinical studies regarding the effects of obesity-induced MIA on peripheral immune cells and microglia priming and their relationship with brain structural alterations in ASD models. Also, we show supportive evidence stating the role of maternal programming on epigenetic gene activation in immune cells of ASD subjects. We suggest that maternal programming by hypercaloric diets during development sets a central and peripheral immune cross-talk which potentially might modulate brain macro and microstructural defects leading to autism susceptibility.