Perinatal inflammation results in decreased oligodendrocyte numbers in adulthood

Glycyrrhizin Attenuates White Matter Injury by Inhibiting Neuroinflammation through the HMGB1/TLR4 Pathway

White matter injury (WMI) is a common complication of preterm birth, potentially resulting in long-term behavioral and motor abnormalities. The objective of this study is to investigate the neuroprotective effects of glycyrrhizin (GLY) on WMI, and try to elucidate the potential mechanisms. In vivo chronic hypoxia-induced WMI mouse model and in vitro oxygen-glucose deprivation (OGD) induced WMI cell model were established, and the effects of GLY on WMI were explored through multiple assays, such as western blotting, immunofluorescence, immunohistochemistry, behavioral experiments, real-time quantitative polymerase chain reaction (RT-qPCR), transmission electron microscope (TEM), molecular docking, and bioinformatics analysis. The results showed that GLY facilitated the maturation and differentiation of oligodendrocytes and enhanced the thickness as well as density of myelin sheaths. GLY also reduced inflammatory response, improved memory, learning, and locomotor performances, and alleviated anxiety in WMI mice. The neuroprotective effects of GLY may be involved in the down-regulation of HMGB1 and its associated proteins such as TLR4 and NF-κB. In conclusion, GLY could mitigate chronic hypoxia-induced WMI and OGD-induced oligodendrocyte injury through its anti-inflammatory effects by inhibiting the HMGB1/TLR4 pathway, suggesting a potential therapeutic avenue for WMI.

Nurturing development: how a mother's nutrition shapes offspring's brain through the gut

Pregnancy is a transformative period marked by profound physical and emotional changes, with far-reaching consequences for both mother and child. Emerging research has illustrated the pivotal role of a mother's diet during pregnancy in influencing the prenatal gut microbiome and subsequently shaping the neurodevelopment of her offspring. The intricate interplay between maternal gut health, nutrition, and neurodevelopmental outcomes has emerged as a captivating field of investigation within developmental science. Acting as a dynamic bridge between mother and fetus, the maternal gut microbiome, directly and indirectly, impacts the offspring's neurodevelopment through diverse pathways. This comprehensive review delves into a spectrum of studies, clarifying putative mechanisms through which maternal nutrition, by modulating the gut microbiota, orchestrates the early stages of brain development. Drawing insights from animal models and human cohorts, this work underscores the profound implications of maternal gut health for neurodevelopmental trajectories and offers a glimpse into the formulation of targeted interventions able to optimize the health of both mother and offspring. The prospect of tailored dietary recommendations for expectant mothers emerges as a promising and accessible intervention to foster the growth of beneficial gut bacteria, potentially leading to enhanced cognitive outcomes and reduced risks of neurodevelopmental disorders.

Perinatal Inflammation Results in Sex-Dependent Cardiac Dysfunction

BACKGROUND

An increased incidence of adult-onset heart failure is seen in individuals born preterm or affected by fetal growth restriction. An adverse maternal environment is associated with both preterm birth and poor fetal development, and postnatal oxygen therapy is frequently required to sustain oxygenation of vulnerable tissues due to lung immaturity.

METHODS

Studies using our murine model of maternal inflammation (LPS) and neonatal hyperoxia exposure (O2) observed pathological changes in cardiac structural proteins and functional analysis with sex dependent differences in pathologies at 10 months of age. Using our previous model, the current investigations tested the hypothesis that early-life perturbations in cardiac structural proteins might predict adult cardiac dysfunction in a sex dependent manner.

RESULTS

LPS-exposed females had lower αMHC mRNA and protein at P0 and P7 relative to the saline-exposed females, but these changes did not persist. Male mice exposed to LPS/O2 had normal expression of αMHC mRNA and protein compared to saline/room air controls though P56, when they dramatically increased. Correlative changes were observed in left ventricular function with a more severe phenotype in the males indicating sex-based differences in cardiac adaptation.

CONCLUSIONS

Our findings demonstrate that early changes in contractile proteins temporally correlate with deficits in cardiac contractility, with a more severe phenotype in males. Our data suggest that similar findings in humans may predict risk for disease in growth-restricted infants.

Myelin Pathology in Alzheimer's Disease: Potential Therapeutic Opportunities

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by memory loss and cognitive decline. Despite significant efforts over several decades, our understanding of the pathophysiology of this disease is still incomplete. Myelin is a multi-layered membrane structure ensheathing neuronal axons, which is essential for the fast and effective propagation of action potentials along the axons. Recent studies highlight the critical involvement of myelin in memory consolidation and reveal its vulnerability in various pathological conditions. Notably, apart from the classic amyloid hypothesis, myelin degeneration has been proposed as another critical pathophysiological feature of AD, which could occur prior to the development of amyloid pathology. Here, we review recent works supporting the critical role of myelin in cognition and myelin pathology during AD progression, with a focus on the mechanisms underlying myelin degeneration in AD. We also discuss the complex intersections between myelin pathology and typical AD pathophysiology, as well as the therapeutic potential of pro-myelinating approaches for this disease. Overall, these findings implicate myelin degeneration as a critical contributor to AD-related cognitive deficits and support targeting myelin repair as a promising therapeutic strategy for AD.

Cerebral Myelination in a Bronchopulmonary Dysplasia Murine Model

INTRODUCTION

Bronchopulmonary dysplasia (BPD) is a devastating disease in preterm infants concurrent with neurodevelopmental disorders. Chronic hyperoxia exposure might also cause brain injury, but the evidence was insufficient.

METHODS

Neonatal C57BL/6J mice were exposed to hyperoxia from P0 to induce a BPD disease model. Lung histopathological morphology analyses were performed at P10, P15, and P20. Cerebral myelination was assessed using MBP (myelin basic protein, a major myelin protein), NfH (neurofilament heavy chain, a biomarker of neurofilament heavy chain), and GFAP (glial fibrillary acidic protein, a marker of astrocytes) as biomarkers by western blot and immunofluorescence.

RESULTS

Mice exposed to hyperoxia exhibited reduced and enlarged alveoli in lungs. During hyperoxia exposure, MBP declined at P10, but then increased to a comparable level to the air group at P15 and P20. Meanwhile, GFAP elevated significantly at P10, and the elevation sustained to P15 and P20.

CONCLUSION

Neonatal hyperoxia exposure caused an arrest of lung development, as well as an obstacle of myelination process in white matter of the immature brain, with a decline of MBP in the generation period of myelin and persistent astrogliosis.

How lung injury and therapeutic oxygen could alter white matter development

Developmental brain injury describes a spectrum of neurological pathologies resulting from either antenatal or perinatal injury. This includes both cognitive and motor defects that affect patients for their entire lives. Developmental brain injury can be caused by a spectrum of conditions including stroke, perinatal hypoxia-ischemia, and intracranial hemorrhage. Additional risk factors have been identified including very low birth weight, mechanical ventilation, and oxygen (O2 ) supplementation. In fact, infants with bronchopulmonary dysplasia, an inflammatory disease associated with disrupted lung development, have been shown to have decreased cerebral white matter and decreased intracranial volumes. Thus, there appears to be a developmental link between the lung, O2 , and the brain that leads to proper myelination. Here, we will discuss what is currently known about the link between O2 and myelination and how scientists are exploring mechanisms through which supplemental O2 and/or lung injury can affect brain development. Consideration of a link between the diseased lung and developing brain will allow clinicians to fine tune their approaches in managing preterm lung disease in order to optimize brain health.

Neonatal Anesthesia and Oxidative Stress

Neonatal anesthesia, while often essential for surgeries or imaging procedures, is accompanied by significant risks to redox balance in the brain due to the relatively weak antioxidant system in children. Oxidative stress is characterized by concentrations of reactive oxygen species (ROS) that are elevated beyond what can be accommodated by the antioxidant defense system. In neonatal anesthesia, this has been proposed to be a contributing factor to some of the negative consequences (e.g., learning deficits and behavioral abnormalities) that are associated with early anesthetic exposure. In order to assess the relationship between neonatal anesthesia and oxidative stress, we first review the mechanisms of action of common anesthetic agents, the key pathways that produce the majority of ROS, and the main antioxidants. We then explore the possible immediate, short-term, and long-term pathways of neonatal-anesthesia-induced oxidative stress. We review a large body of literature describing oxidative stress to be evident during and immediately following neonatal anesthesia. Moreover, our review suggests that the short-term pathway has a temporally limited effect on oxidative stress, while the long-term pathway can manifest years later due to the altered development of neurons and neurovascular interactions.

Multi-Hit White Matter Injury-Induced Cerebral Palsy Model Established by Perinatal Lipopolysaccharide Injection

Cerebral palsy (CP) is a group of permanent, but not unchanging, disorders of movement and/or posture and motor function. Since the major brain injury associated with CP is white matter injury (WMI), especially, in preterm infants, we established a "multi-hit" rat model to mimic human WMI in symptomatology and at a histological level. In our WMI model, pups suffering from limb paresis, incoordination, and direction difficulties fit the performance of CP. Histologically, they present with fewer neural cells, inordinate fibers, and more inflammatory cell infiltration, compared to the control group. From the electron microscopy results, we spotted neuronal apoptosis, glial activation, and myelination delay. Besides, the abundant appearance of IBA1-labeled microglia also implied that microglia play a role during neuronal cell injury. After activation, microglia shift between the pro-inflammatory M1 type and the anti-inflammatory M2 type. The results showed that LPS/infection stimulated IBA1 + (marked activated microglia) expression, downregulated CD11c + (marked M1 phenotype), and upregulated Arg 1 + (marked M2 phenotype) protein expression. It indicated an M1 to M2 transition after multiple infections. In summary, we established a "multi-hit" WMI-induced CP rat model and demonstrated that the microglial activation correlates tightly with CP formation, which may become a potential target for future studies.

Low-body-perfusion via an arterial sheath reduces inflammation after aortic arch reconstruction surgery

Pediatric cardiac surgeries involving aortic arch reconstruction are complex and require long cardiopulmonary bypass (CPB) times with deep hypothermic circulatory arrest (DHCA). Selective perfusion techniques have been developed to prevent the deleterious consequences of DHCA associated hypoperfusion. The effectivity of low body perfusion through cannulation of the femoral artery with an arterial sheath remains to be elucidated. We compared perfusion and inflammation in patients receiving selective antegrade cerebral perfusion (ACP) only to low body perfusion (LBP) in addition to ACP during DHCA for aortic arch reconstruction surgery. There was no difference in patient characteristics, cardiac pathologies, or performed procedures between ACP and LBP groups. Lactate levels increased after cardiac arrest in both groups. However, lactate levels were lower after 1 h reperfusion, at the end of extracorporeal circulation (ECC), and after surgery in LBP group compared to ACP only. Furthermore, creatinine was increased in ACP group on postoperative day 1 compared to LBP group but no acute kidney injury was observed in any group. IL-6 concentration increased in ACP group, while remained unchanged in LBP group compared to pre surgical values and were significantly lower compared to ACP group on postoperative days 1 and 2. LBP via an arterial sheath during cardiac arrest for aortic arch reconstruction surgery in addition to ACP, improves post ECC tissue perfusion as indicated by lower lactate levels and reduces creatinine levels suggesting milder kidney injury. LBP seems to prevent postoperative inflammation through a reduction in procedural duration or enhanced perfusion and thereby improves the outcome after aortic arch reconstruction surgery.

Sex differences in the association between prenatal exposure to maternal obesity and hippocampal volume in children

INTRODUCTION

Animal studies have shown that male but not female offspring exposed to maternal obesity have abnormal hippocampal development. Similar sex differences were observed in animal models of developmental programming by prenatal stress or maternal diabetes. We aimed to translate this work into humans by examining sex-specific effects of exposure to maternal obesity on hippocampal volume in children.

METHODS

Eighty-eight children (37 boys and 51 girls) aged 7-11 years completed the study. Maternal prepregnancy body mass index (BMI) was obtained from electronic medical records. A high-resolution anatomical scan was performed using a 3-Tesla magnetic resonance imaging (MRI) scanner. Total hippocampal volume and hippocampal subfield volumes were analyzed using FreeSurfer 6.0. Linear regression was used to investigate sex differences in relationships between maternal prepregnancy BMI and child hippocampal volume.

RESULTS

Maternal prepregnancy BMI ranged from 19.0 to 50.4 kg/m2 . We observed a significant interaction between maternal prepregnancy BMI and sex on total hippocampal volume (p < .001) such that boys (r = -.39, p = .018) but not girls (r = .11, p = .45) had a significant negative relationship between maternal prepregnancy BMI and total hippocampal volume. This relationship in boys remained significant after adjusting for child and maternal covariates (β = -126.98, p = .012). The sex interactions with prepregnancy BMI were consistently observed in hippocampal subfields CA1 (p = .008), CA2/3 (p = .016), CA4 (p = .002), dentate gyrus (p < .001), and subiculum (p < .001).

CONCLUSIONS

Our results support findings in animal models and suggest that boys may be more vulnerable to the adverse effects of exposure to maternal obesity on hippocampal development than girls.

Maternal prepregnancy body mass index and offspring white matter microstructure: results from three birth cohorts

BACKGROUND AND AIMS

Prepregnancy maternal obesity is a global health problem and has been associated with offspring metabolic and mental ill-health. However, there is a knowledge gap in understanding potential neurobiological factors related to these associations. This study explored the relation between maternal prepregnancy body mass index (BMI) and offspring brain white matter microstructure at the age of 6, 10, and 26 years in three independent cohorts.

SUBJECTS AND METHODS

The study used data from three European birth cohorts (n = 116 children aged 6 years, n = 2466 children aged 10 years, and n = 437 young adults aged 26 years). Information on maternal prepregnancy BMI was obtained before or during pregnancy and offspring brain white matter microstructure was measured at age 6, 10, or 26 years. We used magnetic resonance imaging-derived fractional anisotropy (FA) and mean diffusivity (MD) as measures of white matter microstructure in the brainstem, callosal, limbic, association, and projection tracts. Linear regressions were fitted to examine the association of maternal BMI and offspring white matter microstructure, adjusting for several socioeconomic and lifestyle-related confounders, including education, smoking, and alcohol use.

RESULTS

Maternal BMI was associated with higher FA and lower MD in multiple brain tracts, for example, association and projection fibers, in offspring aged 10 and 26 years, but not at 6 years. In each cohort maternal BMI was related to different white matter tract and thus no common associations across the cohorts were found.

CONCLUSIONS

Maternal BMI was associated with higher FA and lower MD in multiple brain tracts in offspring aged 10 and 26 years, but not at 6 years of age. Future studies should examine whether our observations can be replicated and explore the potential causal nature of the findings.

Inhibitory Effect of LPS on the Proliferation of Oligodendrocyte Precursor Cells through the Notch Signaling Pathway in Intrauterine Infection-induced Rats

Periventricular white matter injury (PWMI) is very common in survivors of premature birth, and the final outcomes are a reduction in myelinated neurons leading to white matter hypomyelination. How and (or) why the oligodendrocyte lineage develops abnormally and myelination is reduced is a hot topic in the field. This study focuses on the effect of intrauterine inflammation on the proliferation of oligodendrocyte lineage cells and the underlying mechanisms. Lipopolysaccharide (LPS) (300 μg/kg) was intraperitoneally injected into pregnant Sprague-Dawley rats at embryonic days 19 and 20 to establish a rat model of intrauterine infection-induced white matter injury. Corpus callosum tissues were collected at postnatal day 14 (P14) to quantify the number of oligodendrocytes, the number and proliferation of oligodendrocyte precursor cells (OPCs), and the expression of myelin proteins (MBP and PLP). Furthermore, the expression of Wnt and Notch signaling-related proteins was analyzed. The results showed that the number of oligodendrocytes in the corpus callosum tissues of LPS-treated rats was reduced, and the expression levels of myelinating proteins were down-regulated. Further analysis showed that the Notch signaling pathway was down-regulated in the LPStreated group. These results indicate that intrauterine LPS may inhibit the proliferation of OPCs by down-regulating the Notch rather than the Wnt signaling pathway, leading to hypomyelination of white matter.

Maternal Glucose Supplementation in a Murine Model of Chorioamnionitis Alleviates Dysregulation of Autophagy in Fetal Brain

Fetal brain injury induced by intrauterine inflammation is a major risk factor for adverse neurological outcomes, including cerebral palsy, cognitive dysfunction, and behavioral disabilities. There are no adequate therapies for neuronal protection to reduce fetal brain injury, especially new strategies that may apply promptly and conveniently. In this study, we explored the effect of maternal glucose administration in a mouse model of intrauterine inflammation at term. Our results demonstrated that maternal glucose supplementation significantly increased survival birth rate and improved the neurobehavioral performance of pups exposed to intrauterine inflammation. Furthermore, we demonstrated that maternal glucose administration improved myelination and oligodendrocyte development in offspring exposed to intrauterine inflammation. Though the maternal blood glucose concentration was temporally prevented from decrease induced by intrauterine inflammation, the glucose concentration in fetal brain was not recovered by maternal glucose supplementation. The adenosine triphosphate (ATP) level and autophagy in fetal brain were regulated by maternal glucose supplementation, which may prevent dysregulation of cellular metabolism. Our study is the first to provide evidence for the role of maternal glucose supplementation in the cell survival of fetal brain during intrauterine inflammation and further support the possible medication with maternal glucose treatment.

Nurr1 expression is modified by inflammation in microglia

Advances in neonatal care have allowed premature infants to survive at earlier gestational ages, but they are often afflicted with neurological delays or deficits. Maternal inflammation has been identified as a major risk factor for premature birth and once born, infants often require supplemental oxygen for survival. Nurr1 (NR4A2) is an orphan nuclear receptor with no known binding site and is essential for the growth of midbrain dopamine neurons. Others have reported that Nurr1 can act as an anti-inflammatory transcription factor in microglia and astrocytes and respond lipopolysaccharide (LPS). We have previously reported decreased numbers of oligodendrocytes and increased numbers of microglia in the mice exposed to both maternal inflammation and neonatal hyperoxia in the perinatal period. These studies tested the hypothesis that the combined exposures to inflammation and hyperoxia would increase Nurr1 expression in microglia in our mouse model and in an immortalized microglia cell line, BV2 cells. Our data indicate that Nurr1 protein expression is increased at postnatal day 0 and postnatal day 28 in whole-brain homogenates from mice exposed to LPS and hyperoxia. Alternatively, Nurr1 message is decreased at postnatal day 60 in isolated microglia, indicating that the increases in whole-brain homogenates may be due to other cell types. In BV2 cells, Nurr1 message in increased by exposure to hyperoxia, but this increase is attenuated in cells exposed to both LPS and hyperoxia. Although Nurr1 regulation is not straightforward, these data indicate that Nurr1 expression is increased in whole-brain homogenates in response to inflammation, but is decreased in isolated primary microglia and BV2 cells in response to similar inflammation. Our data support the hypothesis that Nurr1 expression may play a significant role in regulating inflammation in the brain and understanding the complex regulation of Nurr1 could lead to new therapeutic strategies.

Intrauterine inflammation induces sex-specific effects on neuroinflammation, white matter, and behavior

Exposure to inflammation during pregnancy has been linked to adverse neurodevelopmental consequences for the offspring. One common route through which a developing fetus is exposed to inflammation is with intrauterine inflammation. To that end, we utilized an animal model of intrauterine inflammation (IUI; intrauterine lipopolysaccharide (LPS) administration, 50µg, E15) to assess placental and fetal brain inflammatory responses, white matter integrity, anxiety-related behaviors (elevated zero maze, light dark box, open field), microglial counts, and the CNS cytokine response to an acute injection of LPS in both males and females. These studies revealed that for multiple endpoints (fetal brain cytokine levels, cytokine response to adult LPS challenge) male IUI offspring were uniquely affected by intrauterine inflammation, while for other endpoints (behavior, microglial number) both sexes were similarly affected. These data advance our understanding of sex-specific effects of early life exposure to inflammation in a translationally- relevant model.

Embracing oligodendrocyte diversity in the context of perinatal injury

Emerging evidence is fueling a new appreciation of oligodendrocyte diversity that is overturning the traditional view that oligodendrocytes are a homogenous cell population. Oligodendrocytes of distinct origins, maturational stages, and regional locations may differ in their functional capacity or susceptibility to injury. One of the most unique qualities of the oligodendrocyte is its ability to produce myelin. Myelin abnormalities have been ascribed to a remarkable array of perinatal brain injuries, with concomitant oligodendrocyte dysregulation. Within this review, we discuss new insights into the diversity of the oligodendrocyte lineage and highlight their relevance in paradigms of perinatal brain injury. Future therapeutic development will be informed by comprehensive knowledge of oligodendrocyte pathophysiology that considers the particular facets of heterogeneity that this lineage exhibits.

Minocycline-Suppression of Early Peripheral Inflammation Reduces Hypoxia-Induced Neonatal Brain Injury

While extensive studies report that neonatal hypoxia-ischemia (HI) induces long-term cognitive impairment via inflammatory responses in the brain, little is known about the role of early peripheral inflammation response in HI injury. Here we used a neonatal hypoxia rodent model by subjecting postnatal day 0 (P0d) rat pups to systemic hypoxia (3.5 h), a condition that is commonly seen in clinic neonates, Then, an initial dose of minocycline (45 mg/kg) was injected intraperitoneally (i.p.) 2 h after the hypoxia exposure ended, followed by half dosage (22.5 mg/kg) minocycline treatment for next 6 consecutive days daily. Saline was injected as vehicle control. To examine how early peripheral inflammation responded to hypoxia and whether this peripheral inflammation response was associated to cognitive deficits. We found that neonatal hypoxia significantly increased leukocytes not only in blood, but also increased the monocytes in central nervous system (CNS), indicated by presence of C-C chemokine receptor type 2 (CCR2⁺)/CD11b⁺CD45⁺ positive cells and CCR2 protein expression level. The early onset of peripheral inflammation response was followed by a late onset of brain inflammation that was demonstrated by level of cytokine IL-1β and ionized calcium binding adapter molecule 1(Iba-1; activated microglial cell marker). Interrupted blood-brain barrier (BBB), hypomyelination and learning and memory deficits were seen after hypoxia. Interestingly, the cognitive function was highly correlated with hypoxia-induced leukocyte response. Notably, administration of minocycline even after the onset of hypoxia significantly suppressed leukocyte-mediated inflammation as well as brain inflammation, demonstrating neuroprotection in systemic hypoxia-induced brain damage. Our data provided new insights that systemic hypoxia induces cognitive dysfunction, which involves the leukocyte-mediated peripheral inflammation response.

Effects of therapeutic hypothermia on white matter injury from murine neonatal hypoxia-ischemia

BackgroundTherapeutic hypothermia (TH) is the standard of care for neonates with hypoxic-ischemic encephalopathy, but it is not fully protective in the clinical setting. Hypoxia-ischemia (HI) may cause white matter injury (WMI), leading to neurological and cognitive dysfunction.MethodsP9 mice were subjected to HI as previously described. Pups underwent 3.5 h of systemic hypothermia or normothermia. Cresyl violet and Perl's iron staining for histopathological scoring of brain sections was completed blindly on all brains. Immunocytochemical (ICC) staining for myelin basic protein (MBP), microglia (Iba1), and astrocytes (glia fibrillary acidic protein (GFAP)) was performed on adjacent sections. Volumetric measurements of MBP coverage were used for quantitative analysis of white matter.ResultsTH provided neuroprotection by injury scoring for the entire group (n=44; P<0.0002). ICC analysis of a subset of brains showed that the lateral caudate was protected from WMI (P<0.05). Analysis revealed decreased GFAP and Iba1 staining in hippocampal regions, mostly CA2/CA3. GFAP and Iba1 directly correlated with injury scores of normothermic brains.ConclusionTH reduced injury, and qualitative data suggest that hippocampus and lateral caudate are protected from HI. Mildly injured brains may better show the benefits of TH. Overall, these data indicate regional differences in WMI susceptibility and inflammation in a P9 murine HI model.

Impact of neonatal hypoxia-ischaemia on oligodendrocyte survival, maturation and myelinating potential

Hypoxic-ischaemic episodes experienced at the perinatal period commonly lead to a development of neurological disabilities and cognitive impairments in neonates or later in childhood. Clinical symptoms often are associated with the observed alterations in white matter in the brains of diseased children, suggesting contribution of triggered oligodendrocyte/myelin pathology to the resulting disorders. To date, the processes initiated by perinatal asphyxia remain unclear, hampering the ability to develop preventions. To address the issue, the effects of temporal hypoxia-ischaemia on survival, proliferation and the myelinating potential of oligodendrocytes were evaluated ex vivo using cultures of hippocampal organotypic slices and in vivo in rat model of perinatal asphyxia. The potential engagement of gelatinases in oligodendrocyte maturation was assessed as well. The results pointed to a significant decrease in the number of oligodendrocyte progenitor cells (OPCs), which is compensated for to a certain extent by the increased rate of OPC proliferation. Oligodendrocyte maturation seemed however to be significantly altered. An ultrastructural examination of selected brain regions performed several weeks after the insult showed however that the process of developing central nervous system myelination proceeds efficiently resulting in enwrapping the majority of axons in compact myelin. The increased angiogenesis in response to neonatal hypoxic-ischaemic insult was also noticed. In conclusion, the study shows that hypoxic-ischaemic episodes experienced during the most active period of nervous system development might be efficiently compensated for by the oligodendroglial cell response triggered by the insult. The main obstacle seems to be the inflammatory process modulating the local microenvironment.

Prenatal infection leads to ASD-like behavior and altered synaptic pruning in the mouse offspring

Environmental challenges to the maternal immune system during pregnancy have been associated with an increase in the frequency of neurodevelopmental disorders such as Autism Spectrum Disorders (ASD) appearing in the offspring. Microglia, the brain's resident immune-cells, are now known to be critically involved in normal brain development, shaping connections between neurons by pruning superfluous synaptic spines. Our aim was to investigate whether maternal infection during critical stages of gestation compromises the role of microglia in sculpting neuronal circuits. Using a mouse model of maternal immune activation (MIA) induced by bacterial Lipopolysaccharide (LPS), we assayed the offspring's behavior during postnatal development. Additionally, we quantified spines within the offspring's brain and assessed alterations in some molecular signals involved in pruning. LPS-induced MIA led to behavioral changes relevant to ASD in the offspring in the absence of gross neurological problems. Prenatal LPS resulted in a significant increase in the number of spines in the granule cells of the dentate gyrus, as well as a reduction in hippocampal expression of the fractalkine microglial receptor (CX3CR1), involved in mediating the pruning process in the offspring. Interestingly, these changes were only noted in the male progeny of the LPS challenged dams. These results provide an early indicator that microglial function is altered in the brain of offspring from immune challenged mothers and that the effects in the brain appear to be specific along sex lines.

Human amnion epithelial cells rescue cell death via immunomodulation of microglia in a mouse model of perinatal brain injury

BACKGROUND

Human amnion epithelial cells (hAECs) are clonogenic and have been proposed to reduce inflammatory-induced tissue injury. Perturbation of the immune response is implicated in the pathogenesis of perinatal brain injury; modulating this response could thus be a novel therapy for treating or preventing such injury. The immunomodulatory properties of hAECs have been shown in other animal models, but a detailed investigation of the effects on brain immune cells following injury has not been undertaken. Here, we investigate the effects of hAECs on microglia, the first immune responders to injury within the brain.

METHODS

We generated a mouse model combining neonatal inflammation and perinatal hyperoxia, both of which are risk factors associated with perinatal brain injury. On embryonic day 16 we administered lipopolysaccharide (LPS), or saline (control), intra-amniotically to C57Bl/6 J mouse pups. On postnatal day (P)0, LPS pups were placed in hyperoxia (65% oxygen) and control pups in normoxia for 14 days. Pups were given either hAECs or saline intravenously on P4.

RESULTS

At P14, relative to controls, LPS and hyperoxia pups had reduced body weight, increased density of apoptotic cells (TUNEL) in the cortex, striatum and white matter, astrocytes (GFAP) in the white matter and activated microglia (CD68) in the cortex and striatum, but no change in total microglia density (Iba1). hAEC administration rescued the decreased body weight and reduced apoptosis and astrocyte areal coverage in the white matter, but increased the density of total and activated microglia. We then stimulated primary microglia (CD45lowCD11b+) with LPS for 24 h, followed by co-culture with hAEC conditioned medium for 48 h. hAEC conditioned medium increased microglial phagocytic activity, decreased microglia apoptosis and decreased M1 activation markers (CD86). Stimulating hAECs for 24 h with LPS did not alter release of cytokines known to modulate microglia activity.

CONCLUSIONS

These data demonstrate that hAECs can directly immunomodulate brain microglia, probably via release of trophic factors. This observation offers promise that hAECs may afford therapeutic utility in the management of perinatal brain injury.

Maternal high fat diet exposure is associated with increased hepcidin levels, decreased myelination, and neurobehavioral changes in male offspring

Maternal obesity induces chronic inflammatory responses that impact the fetus/neonate during the perinatal period. Inflammation, iron regulation, and myelination are closely interconnected and disruptions in these processes may have deleterious effects on neurodevelopment. Hepcidin levels are increased in response to inflammation causing subsequent decreases in ferroportin and available iron needed for myelination. Our current studies were designed to test the hypotheses that: 1) maternal high fat diet (HFD) prior to and during pregnancy is sufficient to induce inflammation and alter iron regulation in the brain of the offspring, and 2) HFD exposure is associated with altered myelination and neurobehavioral deficits in the offspring. Our data revealed modest increases in inflammatory cytokines in the serum of dams fed HFD prior to pregnancy compared to dams fed a control diet (CD). Early increases in IL-5 and decreases in IL-10 were observed in serum at PN7 while IL-5 remained elevated at PN21 in the HFD-exposed pups. At PN0, most cytokine levels in whole brain homogenates were higher in the pups born to HFD-fed dams but were not different or were lower than in pups born to CD-fed dams at PN21. Conversely, the inflammation mediated transcription factor Nurr77 remained elevated at PN21. At birth, brain hepcidin, ferroportin, and l-ferritin levels were elevated in pups born to HFD-fed dams compared to pups born to CD-fed dams. Hepcidin levels remained elevated at PN7 and PN21 while ferroportin and l-ferritin levels were lower at PN7 and were not different at PN21. Decreases in myelination in the medial cortex were observed in male but not in female pups born to maternal HFD-fed dams at PN21. These structural changes correlated with changes in behavior (novel object recognition) in at 4months in males only. Our data indicate that maternal obesity (HFD) results in disruption of iron regulation in the brains of the offspring with structural and neurobehavioral deficits in males.

Human Amnion Epithelial Cells Protect Against White Matter Brain Injury After Repeated Endotoxin Exposure in the Preterm Ovine Fetus

Intrauterine inflammation is a significant cause of injury to the developing fetal brain. Using a preterm fetal sheep model of in utero infection, we asked whether human amnion epithelial cells (hAECs) were able to reduce inflammation-induced fetal brain injury. Surgery was undertaken on pregnant sheep at ∼105 days gestation (term is 147 days) for implantation of vascular catheters. Lipopolysaccharide (LPS; 150 ng/kg bolus) or saline was administered IV at 109, 110, and 111 days. Sixty million fluorescent-labeled hAECs were administered at 110, 111, and 112 days gestation via the brachial artery catheter. Brains were collected at 114 days for histological assessment. hAECs were observed within the cortex, white matter, and hippocampus. Compared to control lambs, LPS administration was associated with significant and widespread fetal brain inflammation and injury as evidenced by increased number of activated microglia in the periventricular white matter (p = 0.02), increased pyknosis, cell degeneration (p = 0.01), and a nonsignificant trend of fewer oligodendrocytes in the subcortical and periventricular white matter. Administration of hAECs to LPS-treated animals was associated with a significant mitigation in both inflammation and injury as evidenced by fewer activated microglia (p = 0.03) and pyknotic cells (p = 0.03), significantly more oligodendrocytes in the subcortical and periventricular white matter (p = 0.01 and 0.02, respectively), and more myelin basic protein-positive cells within the periventricular white matter (p = 0.02). hAEC administration to fetal sheep exposed to multiple doses of LPS dampens the resultant fetal inflammatory response and mitigates associated brain injury.

The role of systemic inflammation linking maternal BMI to neurodevelopment in children

Children of obese mothers are at increased risk of developmental adversities. Maternal obesity is linked to an inflammatory in utero environment, which, in turn, is associated with neurodevelopmental impairments in the offspring. This is an integrated mechanism review of animal and human literature related to the hypothesis that maternal obesity causes maternal and fetal inflammation, and that this inflammation adversely affects the neurodevelopment of children. We propose integrative models in which several aspects of inflammation are considered along the causative pathway linking maternal obesity with neurodevelopmental limitations.

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.

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.

Effects of PMA (PHORBOL-12-MYRISTATE-13-ACETATE) on the Developing Rodent Brain

Perinatal infections have a negative impact on brain development. However, the underlying mechanisms leading to neurological impairment are not completely understood and reliable models of inflammation are urgently needed. Using phorbol-myristate-acetate as an activator of inflammation, we investigated the effect on the developing rodent brain. Neonatal rats and mice deficient in IL-18 or IRAK-4 were exposed to PMA. Brains were assessed for regulation of pro- and anti-inflammatory cytokines and cell death 24 hrs, 7 and 14 days after treatment. PMA induced an inflammatory response and caused widespread neurodegeneration in the brains of 3- and 7-day-old rats. In contrast, 14-day-old rats were resistant to the neurotoxic effect of PMA. Histological evaluation at the age of 14 and 21 days revealed a destruction of the cortical microstructure with decreased numerical density of neuronal cells. Mice deficient in IL-18 or IRAK-4 were protected against PMA induced brain injury. PMA treatment during a vulnerable period can alter brain development. IL-18 and IRAK-4 appear to be important for the development of PMA induced injury.

The common antitussive agent dextromethorphan protects against hyperoxia-induced cell death in established in vivo and in vitro models of neonatal brain injury

Preterm infants are prematurely subjected to relatively high oxygen concentrations, even when supplemental oxygen is not administered. There is increasing evidence to show that an excess of oxygen is toxic to the developing brain. Dextromethorphan (DM), a frequently used antitussive agent with pleiotropic mechanisms of action, has been shown to be neuroprotective in various models of central nervous system pathology. Due to its numerous beneficial properties, it might also be able to counteract detrimental effects of a neonatal oxygen insult. The aim of the current study was to evaluate its therapeutic potential in established cell culture and rodent models of hyperoxia-induced neonatal brain injury. For in vitro studies pre- and immature oligodendroglial (OLN-93) cells were subjected to hyperoxic conditions for 48 h after pre-treatment with increasing doses of DM. For in vivo studies 6-day-old Wistar rat pups received a single intraperitoneal injection of DM in two different dosages prior to being exposed to hyperoxia for 24h. Cell viability and caspase-3 activation were assessed as outcome parameters at the end of exposure. DM significantly increased cell viability in immature oligodendroglial cells subjected to hyperoxia. In pre-oligodendroglial cells cell viability was not significantly affected by DM treatment. In vivo caspase-3 activation induced by hyperoxic exposure was significantly lower after administration of DM in gray and white matter areas. In control animals kept under normoxic conditions DM did not significantly influence caspase-3-dependent apoptosis. The present results indicate that DM is a promising and safe treatment strategy for neonatal hyperoxia-induced brain injury that merits further investigation.