Maternal exposure to lipopolysaccharide leads to transient motor dysfunction in neonatal rats

Maternal immune activation accelerates pup reflex development and alters immune proteins in pup stomach contents and brain

Prenatal infection increases the risk for neurodevelopmental disorders including autism spectrum disorder and schizophrenia. To better understand this link, a number of maternal immune activation (MIA) rodent models have been studied. However, the majority of these studies focus on adult behavioural outcomes that mirror adult symptoms related to neurodevelopmental disorders. There is little research reporting the effects of MIA on early postnatal development and even fewer using outbred mouse strains. Here, we use a modified version of the Fox scale to assess the effects of two MIA models, a bacterial model (LPS) and a viral model (PolyIC), on overall mouse pup sensorimotor development in CD-1 mice. Surprisingly, both bacterial and viral MIA models resulted in early reflex development when compared with control pups. To better characterize potential factors related to these changes, we examined indicators of sickness/inflammation in the immune-activated dams and in their pups. Sickness behaviour in the dams resulting from immune activation was assessed using a telemetry implant that allowed for continuous recording of temperature and activity in dams exposed to bacterial or viral immune activation. Although MIA dams showed reduced activity on the day immediately following MIA compared to controls, there was no evidence of fever. All dams showed elevated cytokines/chemokines associated with parturition, but this resolved by day 10 post-parturition and was unaffected by previous immune activation. Although circulating cytokines/chemokines in the dams were similar across MIA treatments, there were differences in the amount of interleukin-12p70 and interleukin-13 present in milk taken from milk bands in MIA pups, and interleukin-4 was overall decreased in LPS pup brain. These findings demonstrate that bacterial and viral models of MIA can result in similar precocious development in mice but differing long-term effects on inflammatory markers in both the milk provided to the pups and in their brains.

Timed fetal inflammation and postnatal hypoxia cause cortical white matter injury, interneuron imbalances, and behavioral deficits in a double-hit rat model of encephalopathy of prematurity

Extreme preterm birth-associated adversities are a major risk factor for aberrant brain development, known as encephalopathy of prematurity (EoP), which can lead to long-term neurodevelopmental impairments. Although progress in clinical care for preterm infants has markedly improved perinatal outcomes, there are currently no curative treatment options available to combat EoP. EoP has a multifactorial etiology, including but not limited to pre- or postnatal immune activation and oxygen fluctuations. Elucidating the underlying mechanisms of EoP and determining the efficacy of potential therapies relies on valid, clinically translatable experimental models that reflect the neurodevelopmental and pathophysiological hallmarks of EoP. Here, we expand on our double-hit rat model that can be used to study EoP disease mechanisms and therapeutic options in a preclinical setting. Pregnant Wistar dams were intraperitoneally injected with 10 μg/kg LPS on embryonic day (E)20 and offspring was subjected to hypoxia (140 min, 8% O2) at postnatal day 4. Rats exposed to fetal inflammation and postnatal hypoxia (FIPH) showed neurodevelopmental impairments, such as reduced nest-seeking ability, ultrasonic vocalizations, social engagement, and working memory, and increased anxiety and sensitivity. Impairments in myelination, oligodendrocyte maturation and interneuron development were examined as hallmarks for EoP, in different layers and coordinates of the cortex using histological and molecular techniques. Myelin density and complexity was decreased in the cortex, which partially coincided with a decrease in mature oligodendrocytes. Furthermore, interneuron populations (GAD67+ and PVALB+) were affected. To determine if the timing of inducing fetal inflammation affected the severity of EoP hallmarks in the cortex, multiple timepoints of fetal inflammation were compared. Inflammation at E20 combined with postnatal hypoxia gave the most severe EoP phenotype in the cortex. In conclusion, we present a double-hit rat model which displays various behavioral, anatomical and molecular hallmarks of EoP, including diffuse white matter injury. This double-hit model can be used to investigate pathophysiological mechanisms and potential therapies for EoP.

Prenatal restraint stress affects early neurobehavioral response and oxidative stress in mice pups

Prenatal stress (PS), in both humans and animals, presents a potential risk to the mother and her fetus throughout gestation. PS is always associated with physiological changes that alter embryonic development and predispose the individual to lifelong health problems, including susceptibility to mental illness. This study aims to identify the harmful effects of prenatal restraint stress (PRS), commonly employed to induce stress painlessly and without any lasting debilitation during gestation. This stress is applied to pregnant Swiss albino mice from E7.5 to delivery for three hours daily. Our results show that PS affects dams' weight gain during the gestational period; moreover, the PS dams prefer passive nursing, exhibit a lower percentage of licking and grooming, and impair other maternal behaviors, including nesting and pup retrieval. Concerning the offspring, this stress induces neurobehavioral impairments, including a significant increase in the time of recovery of the young stressed pups in the surface righting reflex, the latency to avoid the cliff in the cliff avoidance test, longer latencies to accomplish the task in negative geotaxis, and a lower score in swimming development. These alterations were accompanied by increased Malondialdehyde activity (MDA) at PND17 and 21 and downregulation of AchE activity in the whole brain of pups on postnatal days 7 and 9. These findings demonstrated that PS causes deleterious neurodevelopmental impairments that can alter various behaviors later in life.

Persisting neurobehavioral consequences of daily or intermittent paternal cannabis administration in F1 and F2 Rats

Repeated paternal preconception exposure to Δ9-tetrahydrocannabinol (Δ9-THC) alone or together with the other constituents in a cannabis extract has been shown in our earlier studies in rats to cause significant neurobehavioral impairment in their offspring. In the current study, we compared the effects of daily cannabis extract (CE) exposure to cannabis on two consecutive days per week, modeling weekend cannabis use in human. The CE contained Δ9-THC as well as cannabidiol and cannabinol. We also extended the investigation of the study to cross-generational effects of grand-paternal cannabis exposure on the F2 generation and included testing the effects of paternal cannabis exposure on responding for opiate self-administration in F1 and F2 generation offspring. We replicated the findings of neurobehavioral impairment in F1 offspring of male rats exposed to cannabis extract containing 4 mg/kg/day of Δ9-THC daily for four weeks prior to mating with drug naïve females. The 4-week cannabis extract exposure caused a significant decrease in weight gain in the male rats exposed daily. In contrast, their offspring showed significantly greater body weights and anogenital distances (AGD) in the third to fourth weeks after birth. The behavioral effects seen in the F1 generation were increased habituation of locomotor activity in the figure-8 maze in female offspring and increased lever pressing for the opiate drug remifentanil in male offspring. The F2 generation showed significantly impaired negative geotaxis and an elimination of the typical sex-difference in locomotor activity, with effects not seen in the F1 generation. This study shows that daily paternal cannabis exposure for four weeks prior to mating causes significant neurobehavioral impairment in the F1 and F2 offspring. Intermittent exposure on two consecutive days per week for four weeks caused comparable neurobehavioral impairment. In sum, there should be concern about paternal as well as maternal exposure to cannabis concerning neurobehavioral development of their offspring.

Altered Developmental Trajectory in Male and Female Rats in a Prenatal Valproic Acid Exposure Model of Autism Spectrum Disorder

Early motor and sensory developmental delays precede Autism Spectrum Disorder (ASD) diagnosis and may serve as early indicators of ASD. The literature on sensorimotor development in animal models is sparse, male centered, and has mixed findings. We characterized early development in a prenatal valproic acid (VPA) model of ASD and found sex-specific developmental delays in VPA rats. We created a developmental composite score combining 15 test readouts, yielding a reliable gestalt measure spanning physical, sensory, and motor development, that effectively discriminated between VPA and control groups. Considering the heterogeneity in ASD phenotype, the developmental composite offers a robust metric that can enable comparison across different animal models of ASD and can serve as an outcome measure for early intervention studies.

Limosilactobacillus reuteri normalizes blood-brain barrier dysfunction and neurodevelopment deficits associated with prenatal exposure to lipopolysaccharide

Maternal immune activation (MIA) derived from late gestational infection such as seen in chorioamnionitis poses a significantly increased risk for neurodevelopmental deficits in the offspring. Manipulating early microbiota through maternal probiotic supplementation has been shown to be an effective means to improve outcomes; however, the mechanisms remain unclear. In this study, we demonstrated that MIA modeled by exposing pregnant dams to lipopolysaccharide (LPS) induced an underdevelopment of the blood vessels, an increase in permeability and astrogliosis of the blood-brain barrier (BBB) at prewean age. The BBB developmental and functional deficits early in life impaired spatial learning later in life. Maternal Limosilactobacillus reuteri (L. reuteri) supplementation starting at birth rescued the BBB underdevelopment and dysfunction-associated cognitive function. Maternal L. reuteri-mediated alterations in β-diversity of the microbial community and metabolic responses in the offspring provide mechanisms and potential targets for promoting BBB integrity and long-term neurodevelopmental outcomes.

Transcriptional analyses provide novel insights into the transgenerational effects of Poly (I:C) on chickens

Pathogenic microorganisms that are ubiquitous in the environment threaten human health and food safety. Polyinosinic:polycytidylic acid (Poly (I:C)) is a macromolecule with a double-stranded RNA structure, which is often used to simulate viruses. Our previous study found that Poly (I:C) maternal stimulation could affect the reproduction of laying hens and their offspring, but the underlying mechanism needed to be explored. In the present study, splenic transcriptomes were sequenced and analyzed from two groups (Poly (I:C) treatment as the challenged group and saline treatment as the control) and in three generations (maternal stimulated F0 hens, unchallenged F1 and F2 generations). The results showed that Poly (I:C) maternal stimulation affected gene expression patterns in laying hens and their offspring. A total of 27 differentially expressed genes (DEGs) with the same regulating trend were discovered in the F0 and F1 generations, indicating an influence of the intergenerational transmission effect. Functional enrichment analysis of Gene Ontology (GO) showed that lymphocyte differentiation, positive regulation of leukocyte differentiation, positive regulation of MAPK cascade, and T cell differentiation were the common biological processes between F0 and F1 generations, revealing Poly (I:C) could affect the immunity of the treated F0 hens and the unchallenged subsequent generations. Further study showed that pathways associated with growth, development, biosynthesis, and metabolism of F2 chicks were also affected by Poly (I:C) maternal stimulation. Correlation analysis between DEGs and reproductive traits revealed that PHLDA2 (pleckstrin homology-like domain family A member 2) and PODN (podocan) with inheritable effect were highly correlated with egg-laying rate and egg weight in F1 hens, suggesting their potential long-term role in regulating reproductive traits. ARHGAP40, FGB, HRH4, PHLDA2, PODN, NTSR1, and NMU were supposed to play important roles in regulating chickens' immunity and reproductive traits. This study reveals the far-reaching effect on transcriptome induced by Poly (I:C), reflecting the influence of the mother's living environment on the offspring. It is an important reference for future research into the multi-generational transmission of maternal stimulation and harmful environmental factors.

Characterisation of the consequences of maternal immune activation on distinct cell populations in the developing rat spinal cord

Maternal immune activation (MIA) during gestation has been implicated in the development of neurological disorders such as schizophrenia and autism. Epidemiological studies have suggested that the effect of MIA may depend on the gestational timing of the immune challenge and the region of the central nervous system (CNS) in question. This study investigated the effects of MIA with 100 μg/kg lipopolysaccharide at either Embryonic days (E)12 or E16 on the oligodendrocytes, microglia and astrocytes of the offspring spinal cord. At E16, MIA decreased the number of olig2⁺ and Iba‐1⁺ cells in multiple grey and white matter regions of the developing spinal cord 5 h after injection. These decreases were not observed at postnatal day 14. In contrast, MIA at E12 did not alter Olig2⁺ or Iba‐1⁺ cell number in the developing spinal cord 5 h after injection, however, Olig2⁺ cell number was decreased in the ventral grey matter of the P14 spinal cord. No changes were observed in glial fibrillary acidic protein (GFAP) expression at P14 following MIA at either E12 or E16. These data suggest that E16 may be a window of immediate vulnerability to MIA during spinal cord development, however, the findings also suggest that the developmental process may be capable of compensation over time. Potential changes in P14 animals following the challenge at E12 are indicative of the complexity of the effects of MIA during the developmental process.

Long-lasting effects of lipopolysaccharide on the reproduction and splenic transcriptome of hens and their offspring

Lipopolysaccharide (LPS) is ubiquitous in the environment and is released after the death of gram-negative bacteria, which may be related to inflammation and immunosuppression. However, its impact on the reproduction of animals and their offspring, especially the underlying mechanism need further elucidation. Here, we used laying hens as a model organism to investigate the effects of maternal exposure to LPS (LPS maternal stimulation) on animal and their offspring's immunity and reproductive performance, as well as the regulatory role of the transcriptome. We found that the LPS maternal stimulation could reduce the egg-laying rate of hens and their offspring, especially during the early and late laying stages. The transcriptome study of the spleen in F0, F1 and F2 generations showed that the maternal stimulation of the LPS affects the patterns of gene expression in laying hens, and this change has a long-lasting effect. Further analysis of DEGs and their enrichment pathways found that the LPS maternal stimulation mainly affects the reproduction and immunity of laying hens and their offspring. The DEGs such as AVD, HPS5, CATHL2, S100A12, EXFABP, RSFR, LY86, PKD4, XCL1, FOS, TREM2 and MST1 may play an essential role in the regulation of the immunity and egg-laying rate of hens. Furthermore, the MMR1L3, C3, F13A1, LY86 and GDPD2 genes with heritable effects are highly correlated with the egg-laying rate, may have an important reference value for further research. Our study reveals the profound implications of LPS exposure on immunity and reproduction of offspring, elaborating the impact of immune alteration on the egg-laying rate, emphasizing the regulatory role of intergenerational transmission of the transcriptome, implying that the environment parents being exposed to has an important impact on offspring.

Effects of prenatal exposure to inflammation coupled with prepubertal stress on prefrontal white matter structure and related molecules in adult mouse offspring

Maternal immune activation (MIA) by inflammatory agents such as lipopolysaccharide (LPS) and prepubertal stress (PS) may individually and collectively affect the central nervous system (CNS) during adulthood. Here, we intended to assess the effects of MIA, alone or combined with PS, on prefrontal white matter structure and its related molecules in adult mice offspring. Pregnant mice received either an i.p. dose of LPS (50 μg/kg) on gestational day 17 (GD17) or normal saline. Their pups were exposed to stress from postnatal days (PD) 30 to PD38 or no stress during prepubertal development. We randomly chose 56-day-old male offspring (n = 2 offspring per mother) from each group and isolated their prefrontal areas according to relevant protocols. The tissue samples were prepared for structural, histological, and molecular examinations. The LPS + stress group had evidence of increased damage in the white matter structures compared to the control, stress, and LPS groups (p < 0.05). The LPS + stress group also had significant downregulation of the genes involved in white matter formation (Sox10, Olig1, myelin regulatory factor, and Wnt compared with the control, stress, and LPS groups (p < 0.05). In conclusion, although each manipulation individually resulted in small changes in myelination, their combined effects were more pronounced. These changes were parallel to abnormal expression levels of the molecular factors that contribute to myelination.

Cognitive performance during adulthood in a rat model of neonatal diffuse white matter injury

RATIONALE

Infants born prematurely risk developing diffuse white matter injury (WMI), which is associated with impaired cognitive functioning and an increased risk of autism spectrum disorder. Recently, our rat model of preterm diffuse WMI induced by combined fetal inflammation and postnatal hypoxia showed impaired motor performance, anxiety-like behaviour and autism-like behaviour in juvenile rats, especially males. Immunohistochemistry showed delayed myelination in the sensory cortex and impaired oligodendrocyte differentiation.

OBJECTIVE

To assess long-term cognitive deficits in this double-hit rat model of diffuse WMI, animals were screened on impulsivity, attention and cognitive flexibility in adulthood using the 5-choice serial reaction time task (5CSRTT) and a probabilistic reversal learning task, tests that require a proper functioning prefrontal cortex. Thereafter, myelination deficits were evaluated by immunofluorescent staining in adulthood.

RESULTS

Overall, little effect of WMI or sex was found in the cognitive tasks. WMI animals showed subtle differences in performance in the 5CSRTT. Manipulating 5CSRTT parameters resulted in performance patterns previously seen in the literature. Sex differences were found in perseverative responses and omitted trials: female WMI rats seem to be less flexible in the 5CSRTT but not in the reversal learning task. Males collected rewards faster in the probabilistic reversal learning task. These findings are explained by temporally rather than permanently affected myelination and by the absence of extensive injury to prefrontal cortical subregions, confirmed by immunofluorescent staining in both adolescence and adulthood.

CONCLUSION

This rat model of preterm WMI does not lead to long-term cognitive deficits as observed in prematurely born human infants.

Neuronal let-7b-5p acts through the Hippo-YAP pathway in neonatal encephalopathy

Despite increasing knowledge on microRNAs, their role in the pathogenesis of neonatal encephalopathy remains to be elucidated. Herein, we identify let-7b-5p as a significant microRNA in neonates with moderate to severe encephalopathy from dried blood spots using next generation sequencing. Validation studies using Reverse Transcription and quantitative Polymerase Chain Reaction on 45 neonates showed that let-7b-5p expression was increased on day 1 in neonates with moderate to severe encephalopathy with unfavourable outcome when compared to those with mild encephalopathy. Mechanistic studies performed on glucose deprived cell cultures and the cerebral cortex of two animal models of perinatal brain injury, namely hypoxic-ischaemic and intrauterine inflammation models confirm that let-7b-5p is associated with the apoptotic Hippo pathway. Significant reduction in neuronal let-7b-5p expression corresponded with activated Hippo pathway, with increased neuronal/nuclear ratio of Yes Associated Protein (YAP) and increased neuronal cleaved caspase-3 expression in both animal models. Similar results were noted for let-7b-5p and YAP expression in glucose-deprived cell cultures. Reduced nuclear YAP with decreased intracellular let-7b-5p correlated with neuronal apoptosis in conditions of metabolic stress. This finding of the Hippo-YAP association with let-7b needs validation in larger cohorts to further our knowledge on let-7b-5p as a biomarker for neonatal encephalopathy.

Using next generation sequencing of dried blood spots and subsequent validation, Ponnusamy et al identify let-7b-5p as an elevated microRNA in neonates with moderate to severe encephalopathy. Using cell culture and murine models of perinatal brain injury they demonstrate that the effects of let-7b-5p are elicited via the Hippo-YAP pathway, which should be validated in large neonate cohorts to expand our understanding of let-7b-5p as a biomarker for neonatal encephalopathy.

Novel DNA methylation markers of PRRSV-specific antibodies and their intergenerational transmission from pregnant sows to piglets

The main strategy for preventing porcine reproductive and respiratory syndrome (PRRS) is vaccination. However, current commercial porcine reproductive and respiratory syndrome virus (PRRSV) vaccines have limited effectiveness and may even cause infections in pigs. The identification of stable molecular markers associated with immune responses to PRRSV vaccination in pigs provides a new approach for PRRS prevention. DNA methylation, the most stable epigenetic molecular marker related to PRRSV vaccination, has not been investigated. In the current research, we used whole genome bisulfite sequencing (WGBS) to investigate DNA methylation in pregnant sows that received PRRSV vaccination and their piglets with high and low PRRSV-specific antibody levels. By performing methylation data analysis and basing on our previous transcriptomic studies, we identified several differentially methylated genes (DMGs) that are involved in the pathways of inflammatory and immune responses. Among the DMGs, ISG15, MX1, SERPINE1, GNG11 and IFIT3 were common hub genes in the two generations. MX1 and GNG11 were located in quantitative trait loci related with PRRSV antibody titer and PRRSV susceptibility, respectively. These results suggest that PRRSV vaccination in sows induces DNA methylation changes in genes and DNA methylation changes occur through intergenerational transmission. The novel DNA methylation markers and target genes observed in our study provide new insights into the molecular mechanisms of immune responses to PRRSV vaccination across two pig generations.

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

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

Ibuprofen during gestation prevents some changes in physical and reflex development in offspring in a model of hyperleucinemia and maternal inflammation

Maple Syrup Urine Disease (MSUD) is caused by a severe deficiency in the branched-chain ketoacid dehydrogenase complex activity. Patients MSUD accumulate the branched-chain amino acids leucine (Leu), isoleucine, valine in blood, and other tissues. Leu and/or their branched-chain α-keto acids are linked to neurological damage in MSUD. When immediately diagnosed and treated, patients develop normally. Inflammation in MSUD can elicit a metabolic decompensation crisis. There are few cases of pregnancy in MSUD women, and little is known about the effect of maternal hyperleucinemia on the neurodevelopment of their babies. During pregnancy, some intercurrences like maternal infection or inflammation may affect fetal development and are linked to neurologic diseases. Lipopolysaccharide is widely accepted as a model of maternal inflammation. We analyzed the effects of maternal hyperleucinemia and inflammation and the possible positive impact the use of ibuprofen in Wistar rats on a battery of physics (ear unfolding, hair growing, incisors eruption, eye-opening, and auditive channel opening) and neurological reflexes (palmar grasp, surface righting, negative geotaxis, air-righting, and auditory-startle response) maturation parameters in the offspring. Maternal hyperleucinemia and inflammation delayed some physical parameters and neurological reflexes, indicating that both situations may be harmful to fetuses, and ibuprofen reversed some settings.

The Role of Immune Factors in Shaping Fetal Neurodevelopment

Fetal neurodevelopment in utero is profoundly shaped by both systemic maternal immunity and local processes at the maternal-fetal interface. Immune pathways are a critical participant in the normal physiology of pregnancy and perturbations of maternal immunity due to infections during this period have been increasingly linked to a diverse array of poor neurological outcomes, including diseases that manifest much later in postnatal life. While experimental models of maternal immune activation (MIA) have provided groundbreaking characterizations of the maternal pathways underlying pathogenesis, less commonly examined are the immune factors that serve pathogen-independent developmental functions in the embryo and fetus. In this review, we explore what is known about the in vivo role of immune factors in fetal neurodevelopment during normal pregnancy and provide an overview of how MIA perturbs the proper orchestration of this sequence of events. Finally, we discuss how the dysregulation of immune factors may contribute to the manifestation of a variety of neurological disorders.

Lipopolysaccharide-Induced Systemic Inflammation in the Neonatal Period Increases Microglial Density and Oxidative Stress in the Cerebellum of Adult Rats

Inflammatory processes occurring in the perinatal period may affect different brain regions, resulting in neurologic sequelae. Injection of lipopolysaccharide (LPS) at different neurodevelopmental stages produces long-term consequences in several brain structures, but there is scarce evidence regarding alterations in the cerebellum. The aim of this study was to evaluate the long-term consequences on the cerebellum of a systemic inflammatory process induced by neonatal LPS injection. For this, neonatal rats were randomly assigned to three different groups: naïve, sham, and LPS. Saline (sham group) or LPS solution (1 mg/kg) was intraperitoneally injected on alternate postnatal days (PN) PN1, PN3, PN5, and PN7. Spontaneous activity was evaluated with the open field test in adulthood. The cerebellum was evaluated for different parameters: microglial and Purkinje cell densities, oxidative stress levels, and tumor necrosis factor alpha (TNF-α) mRNA expression. Our results show that administration of LPS did not result in altered spontaneous activity in adult animals. Our data also indicate increased oxidative stress in the cerebellum, as evidenced by an increase in superoxide fluorescence by dihydroethidium (DHE) indicator. Stereological analyses indicated increased microglial density in the cerebellum that was not accompanied by Purkinje cell loss or altered TNF-α expression in adult animals. Interestingly, Purkinje cells ectopically positioned in the granular and molecular layers of the cerebellum were observed in animals of the LPS group. Our data suggest that neonatal LPS exposure causes persistent cellular and molecular changes to the cerebellum, indicating the susceptibility of this region to systemic inflammatory insults in infancy. Further investigation of the consequences of these changes and the development of strategies to avoid those should be subject of future studies.

Prenatal cigarette smoke exposure slightly alters neurobehavioral development in neonatal rats: Implications for developmental origins of health and disease (DoHAD)

Numerous studies indicate that smoking during pregnancy exerts harmful effects on fetal brain development. The aim of this study was to determine the influence of maternal smoking during pregnancy on the early physical and neurobehavioral development of newborn rats. Wistar rats were subjected to whole-body smoke exposure for 2 × 40 min daily from the day of mating until day of delivery. For this treatment, a manual closed-chamber smoking system and 4 research cigarettes per occasion were used. After delivery the offspring were tested daily for somatic growth, maturation of facial characteristics and neurobehavioral development until three weeks of age. Motor coordination tests were performed at 3 and 4 weeks of age. We found that prenatal cigarette smoke exposure did not alter weight gain or motor coordination. Critical physical reflexes indicative of neurobehavioral development (eyelid reflex, ear unfolding) appeared significantly later in pups prenatally exposed to smoke as compared to the control group. Prenatal smoke exposure also resulted in a delayed appearance of reflexes indicating neural maturity, including hind limb grasping and forelimb placing reflexes. In conclusion, clinically relevant prenatal exposure to cigarette smoke results in slightly altered neurobehavioral development in rat pups. These findings suggest that chronic exposure of pregnant mothers to cigarette smoke (including passive smoking) results in persisting alterations in the developing brain, which may have long-lasting consequences supporting the concept of developmental origins of health and disease (DoHAD).

Current Evidence on Cell Death in Preterm Brain Injury in Human and Preclinical Models

Despite tremendous advances in neonatal intensive care over the past 20 years, prematurity carries a high burden of neurological morbidity lasting lifelong. The term encephalopathy of prematurity (EoP) coined by Volpe in 2009 encompasses all aspects of the now known effects of prematurity on the immature brain, including altered and disturbed development as well as specific lesional hallmarks. Understanding the way cells are damaged is crucial to design brain protective strategies, and in this purpose, preclinical models largely contribute to improve the comprehension of the cell death mechanisms. While neuronal cell death has been deeply investigated and characterized in (hypoxic–ischemic) encephalopathy of the newborn at term, little is known about the types of cell death occurring in preterm brain injury. Three main different morphological cell death types are observed in the immature brain, specifically in models of hypoxic–ischemic encephalopathy, namely, necrotic, apoptotic, and autophagic cell death. Features of all three types may be present in the same dying neuron. In preterm brain injury, description of cell death types is sparse, and cell loss primarily concerns immature oligodendrocytes and, infrequently, neurons. In the present review, we first shortly discuss the different main severe preterm brain injury conditions that have been reported to involve cell death, including periventricular leucomalacia (PVL), diffuse white matter injury (dWMI), and intraventricular hemorrhages, as well as potentially harmful iatrogenic conditions linked to premature birth (anesthesia and caffeine therapy). Then, we present an overview of current evidence concerning cell death in both clinical human tissue data and preclinical models by focusing on studies investigating the presence of cell death allowing discriminating between the types of cell death involved. We conclude that, to improve brain protective strategies, not only apoptosis but also other cell death (such as regulated necrotic and autophagic) pathways now need to be investigated together in order to consider all cell death mechanisms involved in the pathogenesis of preterm brain damage.

The different effects of viral and bacterial mimics maternal stimuli on ethology of hens and reproduction of their offspring

Environmental stimuli resulting from immunological stress can induce transgenerational phenotypic inheritance, but few similar studies are found in avian. Here, we challenged F0 hens with polyinosinic: polycytidylic acid [Poly(I: C)] and lipopolysaccharide (LPS) at 53 wk of age, and then investigated the ethology of the challenged hens. In the unchallenged F1 descendants, the egg quality at 23 wk of age and laying rate (LR) at different stages were measured. Mortality rate (MR) and the days of population LR reaching 50% (D50%LR) at 33 wk of age were also tested in F1 hens. Pearson correlation analysis was subsequently calculated between F1 peripheral blood lymphocytes transcriptome and LR (in L vs. C) and EW (in P vs. C), respectively. The results showed that the ethology and egg-laying variations of stimuli-challenged hens and their descendants could be affected by the 2 kinds of immune stimuli. Poly(I: C) was likely to increase LR, especially in the early laying period and advance the D50%LR in F1 hens. It also reduced the MR, albumen height, and Haugh units of the unchallenged offspring. Whereas LPS could induce a sickness behavior of the challenged F0 hens, it also reduced the LR of F1 hens throughout the study, prolonged the D50%LR, and faded the eggshell color. Correlation analysis showed that Poly(I: C) mainly affected EW, while LPS mainly influenced LR of F1 offspring. All findings in the present study were the first time to be revealed in laying chickens, suggesting the different effects of Poly(I: C) and LPS on chickens and their descendants, and laying the foundation for the study of the influence of maternal experience on offspring in avian.

LPS-Induced Systemic Neonatal Inflammation: Blockage of P2X7R by BBG Decreases Mortality on Rat Pups and Oxidative Stress in Hippocampus of Adult Rats

Neonatal lipopolysaccharide (LPS) exposure-induced brain inflammation has been associated to neuronal injury and facilitates the development of models of neurological disorders in adult rats. The P2X7 receptor (P2X7R) plays a fundamental role in the onset and maintenance of the inflammatory cascade. Brilliant blue G (BBG), a P2X7R antagonist, has been shown to effectively promote neuroinflammatory protection. Here, we have investigated the long-term effects of the neonatal systemic inflammation on hippocampal oxidative stress, anxiety behavior and pain sensitivity in adulthood. We hypothesized that P2X7R blockade is able to modulate the effects of inflammation on these variables. Male and female rat pups received LPS and/or BBG solution intraperitoneally on the 1st, 3rd, 5th and 7th postnatal days. The survival rate and body weight were evaluated during the experimental procedures. The animals were submitted to behavioral tests for anxiety (elevated plus maze, EPM) and nociception (hot-plate and tail-flick) and the oxidative stress was measured by superoxide production in the dentate gyrus of the hippocampus using dihydroethidium (DHE) probe. BBG increased the survival rate in LPS-treated rats. No significant differences were found regarding anxiety behavior and pain sensitivity between the experimental groups. Systemic neonatal inflammation leads to a higher production of superoxide anion in the dentate gyrus of the hippocampus in adulthood and BBG inhibited that effect. Our data suggest that blocking the activation of the P2X7R during neonatal systemic inflammation may have a potential neuroprotective effect in adulthood.

Neonatal Inhibition of Connexin 36 Ameliorates Fetal Brain Injury Induced by Maternal Noninfectious Fever in Mice

Prenatal fever could result in brain function impairments in the offspring. The present study investigated the effect of interleukin-6 (IL-6)-induced maternal fever on the offspring and the involvement of connexin 36 in this process. Pregnant C57BL/6J mice were injected with IL-6 on gestational day 15. The levels of iNOS and COX-2 were measured as an index of neuroinflammation in the brain of newborn pups. Offspring were treated with the connexin 36 (Cx36) inhibitor mefloquine at postnatal day (P)1-P3 or at P40-P42. Rotarod, grip traction, and foot fault tests were carried out to evaluate the motor behavior of adult offspring. Injection of IL-6 led to an elevation of the core temperature in the pregnant dams. Offspring of these dams showed significantly increased COX-2 and iNOS mRNA expression and protein levels in the whole-brain samples and significantly increased Cx36 in the cerebellum. Moreover, offspring of these dams showed motor deficits at an adult age. Neonatal administration of the Cx36 inhibitor mefloquine could prevent these motor deficits. Maternal fever during pregnancy induced by IL-6 injection could lead to neuroinflammation and motor deficits in the offspring. Neonatal inhibition of Cx36 could ameliorate the motor deficits in the offspring, indicating an involvement of Cx36 in the IL-6-induced maternal fever.

Can Neonatal Systemic Inflammation and Hypoxia Yield a Cerebral Palsy-Like Phenotype in Periadolescent Mice?

Cerebral palsy (CP) is one of the most common childhood-onset motor disabilities, attributed to injuries of the immature brain in the foetal or early postnatal period. The underlying mechanisms are poorly understood, rendering prevention and treatment strategies challenging. The aim of the present study was to establish a mouse model of CP for preclinical assessment of new interventions. For this purpose, we explored the impact of a double neonatal insult (i.e. systemic inflammation combined with hypoxia) on behavioural and cellular outcomes relevant to CP during the prepubertal to adolescent period of mice. Pups were subjected to intraperitoneal lipopolysaccharide (LPS) injections from postnatal day (P) 3 to P6 followed by hypoxia at P7. Gene expression analysis at P6 revealed a strong inflammatory response in a brain region-dependent manner. A comprehensive battery of behavioural assessments performed between P24 and P47 showed impaired limb placement and coordination when walking on a horizontal ladder in both males and females. Exposed males also displayed impaired performance on a forelimb skilled reaching task, altered gait pattern and increased exploratory activity. Exposed females showed a reduction in grip strength and traits of anxiety-like behaviour. These behavioural alterations were not associated with gross morphological changes, white matter lesions or chronic inflammation in the brain. Our results indicate that the neonatal double-hit with LPS and hypoxia can induce subtle long-lasting deficits in motor learning and fine motor skills, which partly reflect the symptoms of children with CP who have mild gross and fine motor impairments.

Transgenerational transmission of maternal stimulatory experience in domesticated birds

The environmental stimuli experienced by a female can influence phenotypes and gene expression in the subsequent generations. We used a specifically designed domesticated-bird model to examine the transgenerational transmission of maternal stimulus exposure, a phenomenon that has been observed but has not been understood in noninbred animals. We subjected parental generation [filial (F)0] hens to viral- or bacterial-like stimulation after artificial insemination. Subsequent filial generations F1 and F2 transmitted growth or fertility variations without further stimulation in contrast to the controls. The whole-genome bisulfite sequence and next-generation mRNA sequencing of peripheral blood lymphocytes (PBLs) from the F1 generation revealed DNA methylome and transcriptome differences in the F1 polyriboinosinic:polyribocytidylic [poly(I:C)] acid or LPS offspring, compared with the F1 controls. In the F1 offspring, DNA methylation changes induced by maternal immune stimulation may have contributed to transcriptional variation. Pathways analysis indicated that the metabolic processes of xenobiotics and drug metabolism pathways, as well as reproduction-related pathways, were involved in the transgenerational transmission of maternal stimulatory experience. Furthermore, LPS-induced transcriptional transmission may have contributed to subfertility, as indicated by the results of comparative analysis between the transcriptomes of spleen tissues across the F0 and F1 generations, as well as the correlative analysis between the transcriptome and reproductive phenotypes. Our findings provide a framework for determining the mechanisms by which maternal stimulatory factors can be inherited transgenerationally with respect to growth, fertility, DNA methylation, and transcriptional levels in outbred animals.-Liu, L., Yang, N., Xu, G., Liu, S., Wang, D., Song, J., Duan, Z., Yang, S., Yu, Y. Transgenerational transmission of maternal stimulatory experience in domesticated birds.

In Utero Administration of Drugs Targeting Microglia Improves the Neurodevelopmental Outcome Following Cytomegalovirus Infection of the Rat Fetal Brain

Congenital cytomegalovirus (CMV) infections represent one leading cause of neurodevelopmental disorders. Recently, we reported on a rat model of CMV infection of the developing brain in utero, characterized by early and prominent infection and alteration of microglia-the brain-resident mononuclear phagocytes. Besides their canonical function against pathogens, microglia are also pivotal to brain development. Here we show that CMV infection of the rat fetal brain recapitulated key postnatal phenotypes of human congenital CMV including increased mortality, sensorimotor impairment reminiscent of cerebral palsy, hearing defects, and epileptic seizures. The possible influence of early microglia alteration on those phenotypes was then questioned by pharmacological targeting of microglia during pregnancy. One single administration of clodronate liposomes in the embryonic brains at the time of CMV injection to deplete microglia, and maternal feeding with doxycyxline throughout pregnancy to modify microglia in the litters' brains, were both associated with dramatic improvements of survival, body weight gain, sensorimotor development and with decreased risk of epileptic seizures. Improvement of microglia activation status did not persist postnatally after doxycycline discontinuation; also, active brain infection remained unchanged by doxycycline. Altogether our data indicate that early microglia alteration, rather than brain CMV load per se, is instrumental in influencing survival and the neurological outcomes of CMV-infected rats, and suggest that microglia might participate in the neurological outcome of congenital CMV in humans. Furthermore this study represents a first proof-of-principle for the design of microglia-targeted preventive strategies in the context of congenital CMV infection of the brain.

A quantitative method for microstructural analysis of myelinated axons in the injured rodent brain

MRI studies (e.g. using diffusion tensor imaging) revealed that injury to white matter tracts, as observed in for instance perinatal white matter injury and multiple sclerosis, leads to compromised microstructure of myelinated axonal tracts. Alterations in white matter microstructure are also present in a wide range of neurological disorders including autism-spectrum disorders, schizophrenia and ADHD. Whereas currently myelin quantity measures are often used in translational animal models of white matter disease, it can be an important valuable addition to study the microstructural organization of myelination patterns in greater detail. Here, we describe methods to extensively study the microstructure of cortical myelination by immunostaining for myelin. To validate these methods, we carefully analyzed the organization of myelinated axons running from the external capsule towards the outer layers of the cortex in three rodent models of neonatal brain injury and in an adult stroke model, that have all been associated with myelination impairments. This unique, relatively easy and sensitive methodology can be applied to study subtle differences in myelination patterns in animal models in which aberrations in myelination integrity are suspected. Importantly, the described methods can be applied to determine efficacy of novel experimental treatments on microstructural organization of cortical myelination.

Systemic inflammation combined with neonatal cerebellar haemorrhage aggravates long-term structural and functional outcomes in a mouse model

BACKGROUND

Despite the increased recognition of cerebellar injury in survivors of preterm birth, the neurodevelopmental consequences of isolated cerebellar injury have been largely unexplored and our current understanding of the functional deficits requires further attention in order to translate knowledge to best practices. Preterm infants are exposed to multiple stressors during their postnatal development including perinatal cerebellar haemorrhage (CBH) and postnatal infection, two major risk factors for neurodevelopmental impairments.

METHODS

We developed a translational mouse model of CBH and/or inflammation to measure the short- and long-term outcomes in cerebellar structure and function.

RESULTS

Mice exposed to early combined insults of CBH and early inflammatory state (EIS) have a delay in grasping acquisition, neonatal motor deficits and deficient long-term memory. CBH combined with late inflammatory state (LIS) does not induce neonatal motor problems but leads to poor fine motor function and long-term memory deficits at adulthood. Early combined insults result in poor cerebellar growth from postnatal day 15 until adulthood shown by MRI, which are reflected in diminished volumes of cerebellar structures. There are also decreases in volumes of gray matter and hippocampus. Cerebellar microgliosis appears 24h after the combined insults and persists until postnatal day 15 in the cerebellar molecular layer and cerebellar nuclei in association with a disrupted patterning of myelin deposition, a delay of oligodendrocyte maturation and reduced white matter cerebellar volume.

CONCLUSIONS

Together, these findings reveal poor outcomes in developing brains exposed to combined cerebellar perinatal insults in association with cerebellar hypoplasia, persistence of microgliosis and alterations of cerebellar white matter maturation and growth.

Maternal Inflammation Results in Altered Tryptophan Metabolism in Rabbit Placenta and Fetal Brain

Maternal inflammation has been linked to neurodevelopmental and neuropsychiatric disorders such as cerebral palsy, schizophrenia, and autism. We had previously shown that intrauterine inflammation resulted in a decrease in serotonin, one of the tryptophan metabolites, and a decrease in serotonin fibers in the sensory cortex of newborns in a rabbit model of cerebral palsy. In this study, we hypothesized that maternal inflammation results in alterations in tryptophan pathway enzymes and metabolites in the placenta and fetal brain. We found that intrauterine endotoxin administration at gestational day 28 (G28) resulted in a significant upregulation of indoleamine 2,3-dioxygenase (IDO) in both the placenta and fetal brain at G29 (24 h after treatment). This endotoxin-mediated IDO induction was also associated with intense microglial activation, an increase in interferon gamma expression, and increases in kynurenine and the kynurenine pathway metabolites kynurenine acid and quinolinic acid, as well as a significant decrease in 5-hydroxyindole acetic acid (a precursor of serotonin) levels in the periventricular region of the fetal brain. These results indicate that maternal inflammation shunts tryptophan metabolism away from the serotonin to the kynurenine pathway, which may lead to excitotoxic injury along with impaired development of serotonin-mediated thalamocortical fibers in the newborn brain. These findings provide new targets for prevention and treatment of maternal inflammation-induced fetal and neonatal brain injury leading to neurodevelopmental disorders such as cerebral palsy and autism.

Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges

Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.

Neurodevelopmental Reflex Testing in Neonatal Rat Pups

Neurodevelopmental reflex testing is commonly used in clinical practice to assess the maturation of the nervous system. Neurodevelopmental reflexes are also referred to as primitive reflexes. They are sensitive and consistent with later outcomes. Abnormal reflexes are described as an absence, persistence, reappearance, or latency of reflexes, which are predictive indices of infants that are at high risk for neurodevelopmental disorders. Animal models of neurodevelopmental disabilities, such as cerebral palsy, often display aberrant developmental reflexes, as would be observed in human infants. The techniques described assess a variety of neurodevelopmental reflexes in neonatal rats. Neurodevelopmental reflex testing offers the investigator a testing method that is not otherwise available in such young animals. The methodology presented here aims to assist investigators in examining developmental milestones in neonatal rats as a method of detecting early-onset brain injury and/or determining the effectiveness of therapeutic interventions. The methodology presented here aims to provide a general guideline for investigators.

Brain damage resulting from postnatal hypoxic-ischemic brain injury is reduced in C57BL/6J mice as compared to C57BL/6N mice

Perinatal hypoxia is a critical complication during delivery and is mostly studied in animal models of postnatal hypoxic-ischemic brain injury. We here studied the effects of postnatal hypoxic-ischemic brain injury in two different sub-strains of C57BL/6 mice, i.e. C57BL/6J and C57BL/6N mice. These two sub-strains show different metabolic properties, for instance an impaired glucose tolerance in C57BL/6J mice. Genetically, this was linked to differences in their nicotinamide nucleotide transhydrogenase (Nnt) genes: In C57BL/6J mice, exons 7-11 of the Nnt gene are deleted, resulting in the absence of functional Nnt protein. The mitochondrial Nnt-protein is one of several enzymes that catalyses the generation of NADPH, which in turn is important for the elimination of reactive oxygen species (ROS). As ROS is thought to contribute to the pathophysiology of hypoxia-ischemia, the lack of Nnt might indirectly increase ROS levels and therefore result in increased brain damage. We therefore hypothesize that lesion score and lesion size will increase in C57BL/6J mice as compared to C57BL/6N mice. Surprisingly, the results showed exactly the opposite: C57BL/6J mice showed a decrease in lesion score and size, associated with a reduced number of apoptotic cells and activated microglia. In contrast, the number of cells with ROS-induced DNA modifications (detected by 8OHdG) was higher in C57BL/6J than C57BL/6N mice. In conclusion, C57BL/6J mice showed reduced ischemic consequences after postnatal hypoxic-ischemic brain injury compared to C57BL/6N mice, with the exception of the amount of ROS-induced DNA-damage. These differences might relate to the lack of Nnt, but also to a modified metabolic setting (cardiovascular parameters, oxygen and glucose metabolism, immune function) in C57BL/6J mice.

Consumption of broccoli sprouts during late gestation and lactation confers protection against developmental delay induced by maternal inflammation

BACKGROUND

The presence of a fetal inflammatory response is linked to cerebral palsy. Unfortunately no preventive therapies are available. In this study, we determined whether dietary supplementation with broccoli sprouts (BrSp), a phase-II enzyme inducer, would be effective in preventing the behavioural and pathologic manifestations in a rodent model of inflammation during late pregnancy.

METHODS

Pregnant Long-Evans rats were administered i.p. Injections of saline (100μl) or lipopolysaccharide (LPS, 200μg/kg), every 12h on embryonic day (E) 19 and 20. In the treatment groups, dams were supplemented with 200mg/day of dried BrSp from E14 until postnatal day 21. Pups underwent a series of neurodevelopmental reflex tests from postnatal day 3-21 followed by neuropathological analyses.

RESULTS

Pups born from the LPS group were significantly growth restricted (p<0.001) and delayed in hindlimb placing (p<0.05), cliff avoidance (p<0.05), and gait (p<0.001) compared to controls. In the open field behaviour analyses, LPS pups had an increase in grooming behaviour (p<0.05) and a decreased amount of time spent in the center of the box compared to controls. Dietary supplementation with BrSp to offspring exposed to LPS had increased birth weights (p<0.001), were no longer delayed in acquiring hindlimb placing, cliff avoidance, gait, and posture, and groomed less compared to LPS alone pups (p<0.01). Histological analyses revealed that LPS pups had reduced myelin basic protein compared to controls.

CONCLUSIONS

Our data suggest that BrSp dietary supplementation during pregnancy may be effective in preventing growth restriction and neurodevelopmental delays.

Impaired oligodendrocyte maturation in preterm infants: Potential therapeutic targets

Preterm birth is an evolving challenge in neonatal health care. Despite declining mortality rates among extremely premature neonates, morbidity rates remain very high. Currently, perinatal diffuse white matter injury (WMI) is the most commonly observed type of brain injury in preterm infants and has become an important research area. Diffuse WMI is associated with impaired cognitive, sensory and psychological functioning and is increasingly being recognized as a risk factor for autism-spectrum disorders, ADHD, and other psychological disturbances. No treatment options are currently available for diffuse WMI and the underlying pathophysiological mechanisms are far from being completely understood. Preterm birth is associated with maternal inflammation, perinatal infections and disrupted oxygen supply which can affect the cerebral microenvironment by causing activation of microglia, astrogliosis, excitotoxicity, and oxidative stress. This intricate interplay of events negatively influences oligodendrocyte development, causing arrested oligodendrocyte maturation or oligodendrocyte cell death, which ultimately results in myelination failure in the developing white matter. This review discusses the current state in perinatal WMI research, ranging from a clinical perspective to basic molecular pathophysiology. The complex regulation of oligodendrocyte development in healthy and pathological conditions is described, with a specific focus on signaling cascades that may play a role in WMI. Furthermore, emerging concepts in the field of WMI and issues regarding currently available animal models are put forward. Novel insights into the molecular mechanisms underlying impeded oligodendrocyte maturation in diffuse WMI may aid the development of novel treatment options which are desperately needed to improve the quality-of-life of preterm neonates.

Loss of Metabotropic Glutamate Receptor 5 Function on Peripheral Benzodiazepine Receptor in Mice Prenatally Exposed to LPS

Parental microglial induced neuroinflammation, triggered by bacterial- or viral infections, can induce neuropsychiatric disorders like schizophrenia and autism to offspring in animal models. Recent investigations suggest that microglia, the resident immune cells of the brain, provides a link between neurotransmission, immune cell activation, brain inflammation and neuronal dysfunction seen with the offspring. Relatively little is known about how reduction of brain inflammation and restoration of glial function are associated with diminution of brain degeneration and behavioral deficits in offspring. Increased mGluR5 expression and the long-lasting excitotoxic effects of the neurotoxin during brain development are associated with the glial dysfunctions. We investigated the relationship of mGluR5 and PBR and how they regulate glial function and inflammatory processes in mice prenatally exposed to LPS (120μg/kg, between gestational days 15 and 17), an inflammatory model of a psychiatric disorder. Using PET imaging, we showed that pharmacological activation of mGluR5 during 5 weeks reduced expression of classic inflammation marker PBR in many brain areas and that this molecular association was not present in LPS-exposed offspring. The post-mortem analysis revealed that the down regulation of PBR was mediated through activation of mGluR5 in astrocytes. In addition, we demonstrated that this interaction is defective in a mouse model of the psychiatric deficit offering a novel insight of mGluR5 involvement to brain related disorders and PBR related imaging studies. In conclusion, mGluR5 driven glutamatergic activity regulates astrocytic functions associated with PBR (cholesterol transport, neurosteroidogenesis, glial phenotype) during maturation and could be associated with neuropsychiatric disorders in offspring.

Considerations for the Optimization of Induced White Matter Injury Preclinical Models

White matter (WM) injury in relation to acute neurologic conditions, especially stroke, has remained obscure until recently. Current advances in imaging technologies in the field of stroke have confirmed that WM injury plays an important role in the prognosis of stroke and suggest that WM protection is essential for functional recovery and post-stroke rehabilitation. However, due to the lack of a reproducible animal model of WM injury, the pathophysiology and mechanisms of this injury are not well studied. Moreover, producing selective WM injury in animals, especially in rodents, has proven to be challenging. Problems associated with inducing selective WM ischemic injury in the rodent derive from differences in the architecture of the brain, most particularly, the ratio of WM to gray matter in rodents compared to humans, the agents used to induce the injury, and the location of the injury. Aging, gender differences, and comorbidities further add to this complexity. This review provides a brief account of the techniques commonly used to induce general WM injury in animal models (stroke and non-stroke related) and highlights relevance, optimization issues, and translational potentials associated with this particular form of injury.

Lipopolysaccharide-Induced Preconditioning Attenuates Apoptosis and Differentially Regulates TLR4 and TLR7 Gene Expression after Ischemia in the Preterm Ovine Fetal Brain

Acute exposure to subclinical infection modulates subsequent hypoxia-ischemia (HI) injury in a time-dependent manner, likely by cross-talk through Toll-like receptors (TLRs), but the specific pathways are unclear in the preterm-equivalent brain. In the present study, we tested the hypothesis that repeated low-dose exposure to lipopolysaccharide (LPS) before acute ischemia would be associated with induction of specific TLRs that are potentially neuroprotective. Fetal sheep at 0.65 gestation (term is ∼145 days) received intravenous boluses of low-dose LPS for 5 days (day 1, 50 ng/kg; days 2-5, 100 ng/kg) or the same volume of saline. Either 4 or 24 h after the last bolus of LPS, complete carotid occlusion was induced for 22 min. Five days after LPS, brains were collected. Pretreatment with LPS for 5 days decreased cellular apoptosis, microglial activation and reactive astrogliosis in response to HI injury induced 24 but not 4 h after the last dose of LPS. This was associated with upregulation of TLR4, TLR7 and IFN-β mRNA, and increased fetal plasma IFN-β concentrations. The association of reduced white matter apoptosis and astrogliosis after repeated low-dose LPS finishing 24 h but not 4 h before cerebral ischemia, with central and peripheral induction of IFN-β, suggests the possibility that IFN-β may be an important mediator of endogenous neuroprotection in the developing brain.

Brain damage of the preterm infant: new insights into the role of inflammation

Epidemiological studies have shown a strong association between perinatal infection/inflammation and brain damage in preterm infants and/or neurological handicap in survivors. Experimental studies have shown a causal effect of infection/inflammation on perinatal brain damage. Infection including inflammatory factors can disrupt programmes of brain development and, in particular, induce death and/or blockade of oligodendrocyte maturation, leading to myelin defects. Alternatively, in the so-called multiple-hit hypothesis, infection/inflammation can act as predisposing factors, making the brain more susceptible to a second stress (sensitization process), such as hypoxic-ischaemic or excitotoxic insults. Epidemiological data also suggest that perinatal exposure to inflammatory factors could predispose to long-term diseases including psychiatric disorders.

Systemic inflammation in early neonatal mice induces transient and lasting neurodegenerative effects

Background

The inflammatory mediator lipopolysaccharide (LPS) has been shown to induce acute gliosis in neonatal mice. However, the progressive effects on the murine neurodevelopmental program over the week that follows systemic inflammation are not known. Thus, we investigated the effects of repeated LPS administration in the first postnatal week in mice, a condition mimicking sepsis in late preterm infants, on the developing central nervous system (CNS).

Methods

Systemic inflammation was induced by daily intraperitoneal administration (i.p.) of LPS (6 mg/kg) in newborn mice from postnatal day (PND) 4 to PND6. The effects on neurodevelopment were examined by staining the white matter and neurons with Luxol Fast Blue and Cresyl Violet, respectively. The inflammatory response was assessed by quantifying the expression/activity of matrix metalloproteinases (MMP), toll-like receptor (TLR)-4, high mobility group box (HMGB)-1, and autotaxin (ATX). In addition, B6 CX3CR1^gfp/+ mice combined with cryo-immunofluorescence were used to determine the acute, delayed, and lasting effects on myelination, microglia, and astrocytes.

Results

LPS administration led to acute body and brain weight loss as well as overt structural changes in the brain such as cerebellar hypoplasia, neuronal loss/shrinkage, and delayed myelination. The impaired myelination was associated with alterations in the proliferation and differentiation of NG2 progenitor cells early after LPS administration, rather than with excessive phagocytosis by CNS myeloid cells. In addition to disruptions in brain architecture, a robust inflammatory response to LPS was observed. Quantification of inflammatory biomarkers revealed decreased expression of ATX with concurrent increases in HMGB1, TLR-4, and MMP-9 expression levels. Acute astrogliosis (GFAP⁺ cells) in the brain parenchyma and at the microvasculature interface together with parenchymal microgliosis (CX3CR1⁺ cells) were also observed. These changes preceded the migration/proliferation of CX3CR1⁺ cells around the vessels at later time points and the subsequent loss of GFAP⁺ astrocytes.

Conclusion

Collectively, our study has uncovered a complex innate inflammatory reaction and associated structural changes in the brains of neonatal mice challenged peripherally with LPS. These findings may explain some of the neurobehavioral abnormalities that develop following neonatal sepsis.

A Critical Review of Models of Perinatal Infection

One of the central, unanswered questions in perinatology is why preterm infants continue to have such poor long-term neurodevelopmental, cognitive and learning outcomes, even though severe brain injury is now rare. There is now strong clinical evidence that one factor underlying disability may be infection, as well as nonspecific inflammation, during fetal and early postnatal life. In this review, we examine the experimental evidence linking both acute and chronic infection/inflammation with perinatal brain injury and consider key experimental determinants, including the microglia response, relative brain and immune maturity and the pattern of exposure to infection. We highlight the importance of the origin and derivation of the bacterial cell wall component lipopolysaccharide. Such experimental paradigms are essential to determine the precise time course of the inflammatory reaction and to design targeted neuroprotective strategies to protect the perinatal brain from infection and inflammation.

Mild intermittent hypoxemia in neonatal mice causes permanent neurofunctional deficit and white matter hypomyelination

Very low birth weight (VLBW) premature infants experience numerous, often self-limited non-bradycardic episodes of intermittent hypoxemia (IH). We hypothesized that these episodes of IH affect postnatal white matter (WM) development causing hypomyelination and neurological handicap in the absence of cellular degeneration. Based on clinical data from ten VLBW neonates; a severity, daily duration and frequency of non-bradycardic IH episodes were reproduced in neonatal mice. Changes in heart rate and cerebral blood flow during IH were recorded. A short-term and long-term neurofunctional performance, cerebral content of myelin basic protein (MBP), 2'3' cyclic-nucleotide 3-phosphodiesterase (CNPase), electron microscopy of axonal myelination and the extent of cellular degeneration were examined. Neonatal mice exposed to IH exhibited no signs of cellular degeneration, yet demonstrated significantly poorer olfactory discrimination, wire holding, beam and bridge crossing, and walking-initiation tests performance compared to controls. In adulthood, IH-mice demonstrated no alteration in navigational memory. However, sensorimotor performance on rota-rod, wire-holding and beam tests was significantly worse compared to naive littermates. Both short- and long-term neurofunctional deficits were coupled with decreased MBP, CNPase content and poorer axonal myelination compared to controls. In neonatal mice mild, non-ischemic IH stress, mimicking that in VLBW preterm infants, replicates a key phenotype of non-cystic WM injury: permanent hypomyelination and sensorimotor deficits. Because this phenotype has developed in the absence of cellular degeneration, our data suggest that cellular mechanisms of WM injury induced by mild IH differ from that of cystic periventricular leukomalacia where the loss of myelin-producing cells and axons is the major mechanism of injury.

The different effects of LPS and poly I:C prenatal immune challenges on the behavior, development and inflammatory responses in pregnant mice and their offspring

In recent years, in vivo animal models of prenatal infection have been developed in an attempt to recreate behavioral and neuropathological features associated to a number of neurological and neuropsychiatric disorders. However, these models are still in their emerging phase and a better understanding of how these types of infections relate to adult-onset of brain-related disorders is needed. Here, we undertook an extensive behavioral characterization of both pregnant females and their pups following late gestational exposure (from gestational days (GD) 15-17) to either lipopolysaccharide (LPS; 120μg/kg i.p.) or polyinosinic:polycytidylic acid (poly I:C; 5mg/kg i.v.). We observed that both LPS and poly I:C treatments produced anxiety-like behaviors in treated pregnant females, although to a lesser extent with LPS. LPS injections, but not poly I:C, led to reduced food intake and consequently decreased weight gain in pregnant dams. In pups, poly I:C treatments triggered a delay in growth and sensorimotor development, as evaluated by righting, geotaxis and grasping reflexes. At the cellular level, both toxins induced an initial inflammatory response while only LPS reduced the expression of brain cell markers in foetuses (GFAP and NeuN), which was no longer observable at postnatal day (PnD) 10. Higher levels of IL-2, IL-5 and IL-6 in plasma and an upregulation of the metabotropic receptor 5 (mGluR5) in foetal brains of 10-day-old offspring prenatally exposed to poly I:C was also observed. Interestingly, the increased mGluR5 expression correlated with impairments of the righting reflex. This study is the first to directly compare reflex development following LPS and poly I:C prenatal immune challenges in mice and sheds light onto the different patterns of behavior and pathology in dams and their offspring.

Inflammatory response and oxidative stress in developing rat brain and its consequences on motor behavior following maternal administration of LPS and perinatal anoxia

Cerebral palsy (CP) is a disorder of locomotion, posture and movement that can be caused by prenatal, perinatal or postnatal insults during brain development. An increased incidence of CP has been correlated to perinatal asphyxia and maternal infections during gestation. The effects of maternal exposure to low doses of bacterial endotoxin (lipopolysaccharide, LPS) associated or not with perinatal anoxia (PA) in oxidative and inflammatory parameters were examined in cerebral cortices of newborns pups. Concentrations of TNF-α, IL-1, IL-4, SOD, CAT and DCF were measured by the ELISA method. Other newborn rats were assessed for neonatal developmental milestones from day 1 to 21. Motor behavior was also tested at P29 using open-field and Rotarod. PA alone only increased IL-1 expression in cerebral cortex with no changes in oxidative measures. PA also induced a slight impact on development and motor performance. LPS alone was not able to delay motor development but resulted in changes in motor activity and coordination with increased levels of IL-1 and TNF-α expression associated with a high production of free radicals and elevated SOD activity. When LPS and PA were combined, changes on inflammatory and oxidative stress parameters were greater. In addition, greater motor development and coordination impairments were observed. Prenatal exposure of pups to LPS appeared to sensitize the developing brain to effects of a subsequent anoxia insult resulting in an increased expression of pro-inflammatory cytokines and increased free radical levels in the cerebral cortex. These outcomes suggest that oxidative and inflammatory parameters in the cerebral cortex are implicated in motor deficits following maternal infection and perinatal anoxia by acting in a synergistic manner during a critical period of development of the nervous system.