Postnatal Day Research Articles

Temporal expression and specific localization of tenomodulin with reference to vascular endothelial growth factor A and calcitonin gene-related peptide in developing diaphragm in mice.

Tenomodulin (TNMD) is related to chondromodulin-1, a cartilage-derived growth regulator. It is specifically expressed in hypovascular connective tissues, including tendons and ligaments. Vascular endothelial growth factor A (VEGF-A) and calcitonin gene-related peptide (CGRP) correlate with angiogenesis and neurogenesis, respectively, during development. Because of that the morphological profiles of TNMD, VEGF-A, and CGRP distributions in developing diaphragm are still unclear, we aimed to determine the expression of mRNA and proteins of these 3 markers during the development of the central tendon of the diaphragm (CTD) and the surrounding diaphragm tissue in mice. Male mice from the embryonic and postnatal periods [embryonic day 14.5 (E14.5), E17.5, postnatal day 1 (P1), and P5] were used and their mRNA and protein expressions were assessed using in situ hybridization, immunohistochemistry and quantitative real-time polymerase chain reaction. The results showed that TNMD was preferentially detected in muscle-tendon junction of the CTD at E17.5 and P1, in contrast to scattered distribution of CGRP and VEGF-A throughout the diaphragm from E14.5 to P5. These findings may provide fundamental information concerning the role of the TNMD in the CTD development.

Pharmacokinetics of 7,8-dihydroxyflavone in neonatal mice with hypoxia-ischemia related brain injury

Introduction7,8-Dihydroxyflavone (7,8-DHF) is a promising translational therapy in several brain injury models, including the neonatal hypoxia-ischemia (HI) model in mice. However, the neuroprotective effect of 7,8-DHF was only observed in female, but not male, neonatal mice with HI brain injury. It is unknown whether HI-induced physiological changes affect brain distribution of 7,8-DHF differently for male versus female mice. We aimed to evaluate the impact of sex on the pharmacokinetics of 7,8-DHF in plasma and brain neonatal mice following experimentally induced HI brain injury.MethodsLeft-sided HI brain injury was induced in postnatal day 9 (P9) mice, followed by a 5 mg/kg intraperitoneal injection of 7,8-DHF. A liquid chromatography-tandem mass spectrometry method was developed to quantitate the drug concentration in plasma samples, as well as in samples from the left and right brain hemispheres. A nonlinear mixed-effects model was used to analyze the plasma and brain concentration-time data. A semi-quantitative approach was used to evaluate the concentrations of two active O-methylated metabolites of 7,8-DHF (8H7M-flavone and 7H8M-flavone) in both plasma and brain samples.ResultsOur PK analyses show that plasma 7,8-DHF concentrations followed a two-compartment PK model, with more than 95% eliminated by 3 h after the IP injection. Sex was not significantly associated with the PK of 7,8-DHF; however, HI brain injury was associated with a 21% reduction in clearance (p < 0.01). The distribution of 7,8-DHF to the brain was rapid; however, the extent of brain distribution was low with the right and left brain-to-plasma partition coefficients being 8.6% and 9.9%, respectively. Additionally, both O-methylated metabolites of 7,8-DHF were detected in the plasma and brain.ConclusionThe plasma and brain PK of 7,8-DHF in neonatal mice were similar between males and females. The low extent of 7,8-DHF brain distribution and the potential effects of the active metabolites should be considered in future studies evaluating the therapeutic effects of 7,8-DHF.

Meta-analysis of retinal transcriptome profiling studies in animal models of myopia

ObjectiveMyopia prevalence is increasing at alarming rates, yet the underlying mechanistic causes are not understood. Several studies have employed experimental animal models of myopia and transcriptome profiling to identify genes and pathways contributing to myopia. In this study, we determined the retinal transcriptome changes in response to form deprivation in mouse retinas. We then conducted a transcriptome meta-analysis incorporating all publicly available datasets and analyzed how the results related to the genes associated with refractive errors in human genome-wide association studies (GWAS).MethodsForm deprivation was induced in three male C57BL6/J mice from postnatal day 28 (P28) to P42. Retinal gene expression was analyzed with RNA sequencing, followed by differential gene expression analysis with DESeq2 and identification of associated pathways with the Kyoto Encyclopedia of Genes and Genomes (KEGG). A systematic search identified four similar retinal transcriptomics datasets in response to experimental myopia using chicks or mice. The five studies underwent transcriptome meta-analyses to determine retinal gene expression changes and associated pathways. The results were compared with genes associated with human myopia.ResultsDifferential gene expression analysis of form-deprived mouse retinas revealed 235 significantly altered transcripts, implicating the BMP2 signaling pathway and circadian rhythms, among others. Transcriptome-wide meta-analyses of experimental myopia datasets found 427 differentially expressed genes in the mouse model and 1,110 in the chick model, with limited gene overlap between species. Pathway analysis of these two gene sets implicated TGF-beta signaling and circadian rhythm pathways in both mouse and chick retinas. Some pathways associated only with mouse retinal changes included dopamine signaling and HIF-1 signaling pathway, whereas glucagon signaling was only associated with gene changes in chick retinas. The follistatin gene changed in both mouse and chick retinas and has also been implicated in human myopia. TGF-beta signaling pathway and circadian entrainment processes were associated with myopia in mice, chicks, and humans.ConclusionThis study highlights the power of combining datasets to enhance statistical power and identify robust gene expression changes across different experimental animal models and conditions. The data supports other experimental evidence that TGF-beta signaling pathway and circadian rhythms are involved in myopic eye growth.

Postnatal development of vasoactive intestinal polypeptide-expressing GABAergic interneurons in mouse somatosensory cortex.

Despite dysfunctional vasoactive intestinal polypeptide-positive interneurons (VIP-INs) being linked to the emergence of neurodevelopmental disorders, the temporal profile of VIP-IN functional maturation and cortical network integration remains unclear. Postnatal VIP-IN development was traced with patch clamp experiments in the somatosensory cortex of Vip-IRES-cre x tdTomato mice. Age groups were chosen during barrel field formation, before and after activation of main sensory inputs, and in adult animals (postnatal days (P) P3-4, P8-10, P14-16, and P30-36). Changes in passive and active membrane properties show a maturation towards accelerated signal integrations. Excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs) showed progressive VIP-IN integration into cortical networks, likely via synaptogenesis: mEPSC frequency increased before P8-10, while mIPSC frequency increased at P14-16. Only mIPSC kinetics became accelerated, and the E/I ratio of synaptic inputs, defined as a ratio of mEPSC to mIPSC charge transfer, remained constant throughout the investigated developmental stages. Evoked (e)EPSCs and (e)IPSCs showed increased amplitudes, while only eIPSCs demonstrated faster kinetics. eEPSCs and eIPSCs revealed a paired-pulse facilitation by P14-16, indicating probably a decrease in the presynaptic release probability (pr) and a paired-pulse depression in adulthood. eIPSCs also showed the latter, suggesting a decrease in pr for both signal transmission pathways at this time point. VIP-INs mature towards faster signal integration and pursue different strategies to avoid overexcitation. Excitatory and inhibitory synaptic transmission become stronger and shorter via different pre- and postsynaptic alterations, likely promoting the execution of active whisking.

Endothelial Cpt1a Inhibits Neonatal Hyperoxia-Induced Pulmonary Vascular Remodeling by Repressing Endothelial-Mesenchymal Transition.

Pulmonary hypertension (PH) increases the mortality of preterm infants with bronchopulmonary dysplasia (BPD). There are no curative therapies for this disease. Lung endothelial carnitine palmitoyltransferase 1a (Cpt1a), the rate-limiting enzyme of the carnitine shuttle system, is reduced in a rodent model of BPD. It is unknown whether endothelial Cpt1a reduction causes pulmonary vascular (PV) remodeling. The latter can be the result of endothelial-mesenchymal transition (EndoMT). Here, endothelial cell (EC)-specific Cpt1a KO and WT mice (<12h old) are exposed to hyperoxia (70% O2) for 14 days and allow them to recover in normoxia until postnatal day 28. Hyperoxia causes PH, which is aggravated in EC-specific Cpt1a KO mice. Upregulating endothelial Cpt1a expression inhibits hyperoxia-induced PV remodeling. Hyperoxia causes lung EndoMT, detected by immunofluorescence, scRNA-sequencing, and EC lineage tracing, which is further increased in EC-specific Cpt1a KO mice. Blocking EndoMT inhibits hyperoxia-induced PV remodeling. Male mice under the same high oxygen conditions develop a higher degree of PH than females, which is associated with reduced endothelial Cpt1a expression. Conclusively, neonatal hyperoxia causes PH by decreasing endothelial Cpt1a expression and upregulating EndoMT. This provides a valuable strategy for developing targeted therapies by upregulating endothelial Cpt1a levels or inhibiting EndoMT to treat BPD-associated PH.

Cerebrospinal Fluid Composition of Infants with Ischemic Stroke.

To characterize the cerebrospinal fluid (CSF) of infants with stroke and compare those findings to the CSF of infants with bacterial meningitis and neither condition in the first 14 postnatal days. Cohort study of 30,092 infants who received a lumbar puncture in the first 14 postnatal days discharged from >300 neonatal intensive care units from 1997-2020. CSF parameters were compared between infants with stroke and bacterial meningitis using non-parametric hypothesis testing and quantile regression. Compared to infants with bacterial meningitis, infants with stroke had a significantly lower median protein concentration, higher median glucose concentration, higher median red blood cell count, and higher median monocyte count. Using quantile regression, at the 75th percentile infants with stroke had a significantly lower white blood cell count, segmented neutrophil count, and lymphocyte count than infants with bacterial meningitis. This study addresses the paucity of literature describing the cerebrospinal fluid of infants with ischemic stroke. Knowledge of the differences in CSF parameters between infants with stroke and meningitis may allow for faster recognition and intervention before CSF culture results are available.

Identification of a Subpopulation of Astrocyte Progenitor Cells in the Neonatal Subventricular Zone: Evidence that Migration is Regulated by Glutamate Signaling

In mice engineered to express enhanced green fluorescent protein (eGFP) under the control of the entire glutamate transporter 1 (GLT1) gene, eGFP is found in all ‘adult’ cortical astrocytes. However, when 8.3 kilobases of the human GLT1/EAAT2 promoter is used to control expression of tdTomato (tdT), tdT is only found in a subpopulation of these eGFP-expressing astrocytes. The eGFP mice have been used to define mechanisms of transcriptional regulation using astrocytes cultured from cortex of 1–3 day old mice. Using the same cultures, we were never able to induce tdT+ expression. We hypothesized that these cells might not have migrated into the cortex by this age. In this study, we characterized the ontogeny of tdT+ cells, performed single-cell RNA sequencing (scRNA-seq), and tracked their migration in organotypic slice cultures. At postnatal day (PND) 1, tdT+ cells were observed in the subventricular zone and striatum but not in the cortex, and they did not express eGFP. At PND7, tdT+ cells begin to appear in the cortex with their numbers increasing with age. At PND1, scRNA-seq demonstrates that the tdT+ cells are molecularly heterogeneous, with a subpopulation expressing astrocytic markers, subsequently validated with immunofluorescence. In organotypic slices, tdT+ cells migrate into the cortex, and after 7 days they express GLT1, NF1A, and eGFP. An ionotropic glutamate receptor (iGluR) antagonist reduced by 50% the distance tdT+ cells migrate from the subventricular zone into the cortex. The pan-glutamate transport inhibitor, TFB-TBOA, increased, by sixfold, the number of tdT+ cells in the cortex. In conclusion, although tdT is expressed by non-glial cells at PND1, it is also expressed by glial progenitors that migrate into the cortex postnatally. Using this fluorescent labeling, we provide novel evidence that glutamate signaling contributes to the control of glial precursor migration.

Transcriptomic Analysis of Effects of Developmental PCB Exposure in the Hypothalamus of Female Rats.

This study investigated the consequences of perinatal exposure to Aroclor 1221 (A1221), a weakly estrogenic polychlorinated biphenyl (PCB) mixture and known endocrine-disrupting chemical (EDC), in female rats. Previous work has shown behavioral and physiological effects of A1221, and the current study extended this work to comprehensive transcriptomic profiling of two hypothalamic regions involved in the control of reproduction: the arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV). Female Sprague-Dawley rats were fed a cookie treated with a small volume of A1221 (1 mg/kg) or vehicle (3% DMSO in sesame oil) during pregnancy from gestational days 8-18 and after birth from postnatal (P) days 1-21, exposing the offspring via placental and lactational transfer. In female offspring, developmental, physiological, and hormonal effects of A1221 were relatively modest. However, because prior work has implicated this exposure in neurobehavioral disruptions, we sought to determine whether developmental programming of the brain transcriptome could underlie these phenotypes. We used 3' targeted RNA sequencing in the hypothalamus (arcuate nucleus, anteroventral periventricular nucleus) of experimental females at P8, 30, and 60 and identified significant alterations in gene expression and gene ontology (GO) terms in an age- and tissue-specific manner. Most notably, terms related to synaptic signaling, neurotransmitter regulation, immune response, and cellular structure were identified. Changes in pathways associated with synaptic functions and cellular metabolism were further identified, indicating that A1221 exposure can impact neurodevelopmental and neuroendocrine processes at a molecular level, even in the absence of overt developmental changes. These findings of molecular reprogramming may explain the behavioral effects of A1221 and highlight novel molecular targets and pathways that warrant further investigation to understand the effects of EDCs on the developing brain.

Neurosteroid replacement therapy using tiagabine and zuranolone restores cerebellar neurodevelopment and reduces hyperactive behaviour following preterm birth.

Preterm birth exposes the neonate to hypoxic-ischaemic and excitotoxic insults that impair neurodevelopment and are magnified by the premature loss of placentally supplied, inhibitory neurosteroids. The cerebellum is a neuronally dense brain region, which undergoes critical periods of development during late gestation, when preterm births frequently occur. We propose that neurosteroid replacement therapy using tiagabine and zuranolone will protect the cerebellum against preterm-associated insults. Guinea pig dams received c-section surgery preterm (gestational age (GA) 64) or at term (GA70) with preterm pups administered tiagabine (2.5 mg/kg/day), zuranolone (1 mg/kg/day) or vehicle (15% β-cyclodextrin) until term equivalent age (GA70). Behavioural testing was performed at corrected postnatal day 8 (PND8) and PND41 with tissue collection occurring at PND42. Neurodevelopmental markers (MBP, OLIG2 and NeuN) were assessed within the cerebellum by immunohistochemistry, whilst GABAergic and glutamatergic pathway expression was quantified using high throughput RT-PCR. Zuranolone and, to a lesser extent, tiagabine were able to protect against hyperactive behaviour at PND8 in males, whilst in females, a less marked hyperactive phenotype was present with neither treatment impacting behaviour further. Both treatments improved MBP staining, whilst tiagabine was found to restore oligodendrocyte maturation in females only. GABAergic and glutamatergic pathway expression was found to be restored by both treatments in females. Overall, this study demonstrates the neuroprotective attributes of neurosteroid replacement therapy using tiagabine and zuranolone, thereby demonstrating their potential to mitigate long-term neurodevelopmental impairments. Furthermore, the sexually dimorphic effects observed suggest future investigations may show increased benefit by using sex-specific treatment regimes.

Human umbilical cord mesenchymal stem cell-derived exosomes combined with mouse nerve growth factor can more effectively ameliorate the motor disorder and brain pathological injury in mice with cerebral palsy.

Cerebral palsy (CP) is a neurodevelopmental disorder and motor disorder syndrome. It has been confirmed that mesenchymal stem cells (MSCs) and mouse nerve growth factor (mNGF) can repair brain tissue damage and nerve injury; however, exosomes derived from healthy cells may have a comparable therapeutic potential as the cells themselves. The purpose of this study was to explore the improvement effect of human umbilical cord mesenchymal stem cell (hUC-MSCs)-derived exosomes on a CP model and determine whether there is a synergistic effect when combined with mNGF. Exosomes were isolated from hUC-MSCs and examined using transmission electron microscopy (TEM), particle size and western blot (WB). A total of 38 BALB/c mice (male, postnatal day 6 (PND6)) were randomly divided into 5 groups: sham group, CP group, CP-exo group, CP-mNGF group, and CP-exo-mNGF group. Hypoxic induction after unilateral common carotid artery ligation combined with lipopolysaccharide (LPS) infection was used to construct the CP model. Pathological damage to neuron tissue and synaptic structures in the hippocampus was confirmed using light microscopy after hematoxylin-eosin (H&E) staining and TEM, respectively. Survival of neurons was evaluated using Nissl staining. Western blot was applied to monitor PSD-95 and synaptophysin (SYN) protein levels. This study indicated that exosomes released by hUC-MSCs ameliorated brain damage and synaptic structure destruction in CP mice induced by hypoxic ischemia and LPS infection. When combined with mNGF, there was more effective improvement. In the CP group, neuronal function was severely impaired; however, hUC-MSCs-derived exosomes and mNGF improved it. PSD-95 and SYN proteins were presynaptic and postsynaptic proteins, respectively. Interestingly, the PSD-95 and SYN protein levels were significantly lower in the CP mice, but with the addition of hUC-MSCs-exosomes or mNGF, they increased significantly, especially in the CP-exo-mNGF group. The nerve function injury in CP can be improved the most when hUC-MSCs-derived exosomes are combined with mNGF through intraperitoneal (ip.) administration.

MYO7A is required for the functional integrity of the mechanoelectrical transduction complex in hair cells of the adult cochlea

Myosin-VIIA (MYO7A) is an unconventional myosin responsible for syndromic (Usher 1B) or nonsyndromic forms of deafness in humans when mutated. In the cochlea, MYO7A is expressed in hair cells, where it is believed to act as the motor protein tensioning the mechanoelectrical transducer (MET) channels, thus setting their resting open probability (Po). However, direct evidence for this unique role for an unconventional myosin in mature hair cells is lacking. Here, we show that MYO7A has a distinct role in hair cells, being crucial for the structural integrity of hair bundles. Postnatal deletion of Myo7a leads to 87 to 96% reduction in MYO7A from hair cells by postnatal day 20 (P20), without affecting hearing function. During the following week, mice showed progressive decline in both hearing function and MET current amplitude in hair cells without affecting the resting Po and calcium sensitivity of the MET channel. Hair-bundle stiffness was normal at P20 but halved at P30, despite it having a normal staircase morphology and tip links. The reduction of MYO7A in the stereocilia (>87%) increased their vulnerability to sound-induced damage, with significantly more hearing loss and hair bundle deterioration than in control mice. RNA-sequencing identified a downregulation of several stereociliary genes in the Myo7a-deficient cochlea, indicating the presence of indirect compensatory mechanisms. This study reveals that mature hair cells seem to use a MYO7A-independent mechanism to maintain the resting Po of the MET channels. Instead, MYO7A is essential for maintaining the structural and functional integrity of the hair bundles.

Maternal aspartame exposure alters lung Th1/Th2 cytokine balance in offspring through nuclear factor-κB activation.

Epidemiological evidence suggests that maternal intake of nonnutritive sweeteners is positively associated with early childhood asthma incidence. We investigated the effects of maternal aspartame exposure during pregnancy and lactation on lung Th1/Th2 cytokine balance and intestinal microbiota in offspring and explored the mechanisms that mediate these effects. Pregnant BALB/c mice were randomly divided on gestational day 7 into two dietary intervention groups: control (drinking water only) and aspartame (drinking water+0.25g/L aspartame) groups. The dams nursed their offspring for 3weeks. On postnatal day 21, heart blood samples were collected, and immunoglobulin E levels were measured. Microorganisms from the lower gastrointestinal tract were sampled using a culture-independent approach. Lung tissues were harvested for biochemical analyses. Maternal aspartame exposure increased the body weight of the dams from gestational day 7 to postnatal day 21 and the body weight of the offspring from birth to postnatal day 21. Maternal aspartame exposure significantly increased the levels of Th2 cytokines (interleukin [IL]-4, IL-5, and IL-13) and IL-17 and immunoglobulin E but reduced that of a Th1 cytokine (interferon-γ) in the offspring's lung tissues. The altered Th1/Th2 balance was accompanied by increased lung nuclear factor-κB activation. The bacterial composition and alpha-diversity of the gut microbiota of the offspring did not differ significantly between the control and aspartame groups. Our findings suggest maternal aspartame exposure influences lung Th1/Th2 cytokine balance in offspring through nuclear factor-κB activation.

Effects of Cannabidiol Isolated or in Association With Risperidone in an Animal Model of Autism.

Autism spectrum disorder (ASD) is characterized by deficits in communication, social interaction, and repetitive and stereotyped behaviors, with no specific drug therapy available. Studies have found that cannabidiol (CBD) can improve hyperactive and cognitive symptoms in children with ASD. However, little is known about the effect of CBD in combination with other medications, such as risperidone (RISP). This study aimed to evaluate the behavioral and biochemical effects of CBD in animals using a valproic acid (VPA)-induced ASD animal model. VPA was administered in pregnant Wistar rats on Day 12.5 of gestation to induce the ASD model. From the 10th to the 16th postnatal day (PND), the neurodevelopment of the animals was assessed through eye-opening, olfactory discrimination, and negative geotaxis behavioral tests. From PNDs 9 to 54, the animals were weighed. They were treated for 21 days with CBD alone (100mg/kg, by gavage, twice a day) or in combination with RISP (0.1mg/kg, by gavage, once a day). At PND 55, the animals were evaluated in social interaction and locomotor activity experiments. Finally, after behavioral assessment, the animals were euthanized, the brain was isolated, and oxidative stress parameters were evaluated in the hippocampus and cortex posterior. Animals exposed to VPA showed neurodevelopmental delays in opening their eyes, difficulties in turning around their axis, and took longer time to find the original nest when compared to control animals. They also exhibited impaired sociability and reduced exploratory activity, which indicates model impairments. Interestingly, animals exposed to VPA treated with CBD+RISP significantly improved sociability parameters, whereas isolated CBD did not affect this parameter. In the biochemical analysis, a significant decrease in the hippocampal sulfhydryl content was noted in the CT+CBD group and an increase in the VPA+CBD group. In conclusion, these results suggest that CBD, in combination with RISP, may be an interesting pharmacological approach to reducing ASD-related symptoms. Summary: Besides the increased prevalence of ASD cases in recent years, there are no medications to improve the central symptoms of autism. Numerous studies discuss CBD as an important medication for improving ASD symptoms; however, it is not known how CBD interacts with commonly used drugs in ASD individuals, such as RISP. This study demonstrated that CBD therapy, only when combined with RISP, improved sociability in a VPA-induced ASD animal model.

Early-life bisphenol A exposure causes detrimental age-related changes in anxiety, depression, learning, and memory in juvenile and adult male rats: Involvement of NMDAR/PSD-95–PTEN/AKT signaling pathway

Bisphenol A (BPA) is an endocrine disruptor monomer that is widely used in the manufacturing of epoxy resins and polycarbonate plastics. Several lines of evidence indicate the function of the pre- or perinatally PI3K/AKT signaling pathway in the development of psychiatric disorders. The present study aimed to evaluate for the first time the effect of modifying the NMDAR/PSD-95–PTEN/AKT signaling pathway on behavioral and synaptic plasticity of early-life BPA exposure and its long-lasting influence on juvenile and adulthood stages of development. We investigated the effects of oral BPA doses of 50 and 125mg/kg/day on the prefrontal cortex (PFC) and hippocampus of male Sprague Dawley rats from postnatal day (PND) 18–60 and PND 18–95, which correspond to juvenile and adolescent stages, respectively. Subsequently, we performed a series of rat behavioral tests, including the open field, elevated plus-maze, forced swimming, and Y-maze. Notably, neurotransmitter levels such as dopamine, serotonin, and gamma-aminobutyric acid, levels of postsynaptic density protein 95 and cAMP response element-binding protein, as well as mRNA levels of N-methyl-D-aspartate receptor subunits, fluctuated between reduction and elevation in the PFC and hippocampus. Furthermore, phosphatase and tensin (PTEN) mRNA and protein levels were upregulated in both brain areas, while PI3K, protein kinase B (AKT) and mammalian target of rapamycin (mTOR) mRNA and protein levels were decreased. Finally, our findings indicate that postnatal BPA exposure promotes long-term anxiety and depressive-like behaviors, as well as cognitive impairment, via modulation of the NMDAR/PSD-95–PTEN/AKT pathway. These findings could help to elucidate the potential developmental and neurobehavioral effects of early-life BPA exposure.

Early-life sodium restriction programs autonomic dysfunction and salt sensitivity in male C57BL/6J mice.

Preterm birth increases the risk of cardiometabolic disease in adulthood. Infants born during the second trimester of pregnancy, a critical period of hypothalamic development, are at risk of sodium (Na) depletion due to renal immaturity and large urine Na losses. We previously demonstrated in male mice that Na restriction during the equivalent mouse hypothalamic development period [postnatal day (PD)21-PD42] programs long-term changes in energy balance via increased thermogenic sympathetic nervous activity. We therefore hypothesized that early-life Na restriction programs changes in cardiovascular control via altered autonomic activity. C57BL/6J male mice were supplied a low (0.04%) Na or supplemented (0.30%) Na diet from PD21 to PD42, before return to standard (0.15%) Na diet. Hemodynamic and autonomic functions were assessed by radiotelemetry and acute administration of autonomic antagonists before and after all animals were switched to a high Na diet (HSD; 1% Na) at 12 wk of age. Mice were additionally treated with the angiotensin II type 1 receptor antagonist losartan for 2 wk. On standard diet, early-life Na restriction resulted in small but significantly different hemodynamic responses to autonomic blockers without any effect on systolic blood pressure (SBP) or heart rate. HSD increased SBP in 0.04% but not 0.30% Na mice, accompanied by increased cardiac sympathetic activity. Losartan had a greater BP-lowering effect in early-life Na-restricted mice. Our findings suggest that Na restriction during a critical hypothalamic developmental period programs long-term changes in the autonomic control of cardiovascular functions and may offer insight into the increased risk of cardiovascular disease in former preterm infants.NEW & NOTEWORTHY Mechanisms by which preterm birth increases the risk of adult-onset cardiometabolic diseases are not well understood. The renin-angiotensin system (RAS) has been implicated in the programming of adult disease, although contributors to RAS dysregulation remain to be identified. Findings from this study suggest that failure to maintain postnatal sodium homeostasis during a critical developmental window may contribute to RAS dysregulation and the risk of salt sensitivity of autonomic and cardiovascular function.

Gene Expression After Exercise Is Disrupted by Early-Life Stress.

Exercise can be leveraged as an important tool to improve neural and psychological health, either on its own or to bolster the efficacy of evidence-based treatment modalities. Research in both humans and animal models shows that positive experiences, such as exercise, promote neuroprotection while, in contrast, aversive experiences, particularly those in early development, are often neurologically and psychologically disruptive. In the current study, we employed a preclinical model to investigate the therapeutic benefits of exercise on gene expression in the brains of adult rats. Long Evans rats were exposed to maltreatment stress or nurturing care during infancy, with some rats later given voluntary running wheels as an aerobic exercise intervention from Postnatal Days 70 to 90. Our results showed that irisin gene expression, which promotes neuroprotection, was differentially affected by exercise and early exposure to stress. We add to a rapidly growing area of research on the neuroprotective benefits of exercise and shed light on important molecular mechanisms that may affect the efficacy of exercise in different individuals.

Prenatal exposure to valproic acid induces sex-specific alterations in rat cortical and hippocampal neuronal structure and function in vitro.

There are substantial differences in the characteristics of males and females with an autism spectrum disorder (ASD), yet there is little knowledge surrounding the mechanistic underpinnings of these differences. The valproic acid (VPA) rodent model is based upon the human fetal valproate spectrum disorder, which is associated with increased risk of developing ASD. This model, which displays significant social, learning, and memory alterations, has therefore been widely used to further our understanding of specific biological features of ASD. However, to date, almost all of the studies employing this model have used male rodents. To fill this knowledge gap, we evaluated sex differences for neuronal activity, morphology, and glycogen synthase kinase-3 (GSK-3) signaling in primary cortical (CTX) and hippocampal (HIP) neurons prepared from rats exposed to VPA in utero. In vivo, sex-specific VPA-induced alterations in the frontal CTX transcriptome at birth were also determined. Overall, VPA induced more robust changes in neuronal function and structure in the CTX than in the HIP. Male- and female-derived primary CTX neurons from rats exposed to prenatal VPA had elevated activity and showed more disorganized firing. In the HIP, only the female VPA neurons showed elevated firing, while the male VPA neurons exhibited disorganized activity. Dendritic arborization of CTX neurons from VPA rats was less complex in both sexes, though this was more pronounced in the females. Conversely, both female and male HIP neurons from VPA rats showed elevated complexity distal to the soma. Female VPA CTX neurons also had an elevated number of dendritic spines. The relative activity of the α and β isoforms of GSK-3 were suppressed in both female and male VPA CTX neurons, with no changes in the HIP neurons. On postnatal day 0, alterations in CTX genes associated with neuropeptides (e.g., penk, pdyn) and receptors (e.g., drd1, adora2a) were seen in both sexes, though they were downregulated in females and upregulated in males. Together these findings suggest that substantial sex differences in neuronal structure and function in the VPA model may have relevance to the reported sex differences in idiopathic ASD.

Defective Hippocampal Primary Ciliary Function and Aberrant LKB1/AMPK Signaling Pathway Are Associated With the Inhibition of Autophagic Activity in Offspring Born to Mothers of Advanced Maternal Age.

Advanced maternal age (AMA) negatively influences the development and cognitive functions of offspring. However, the underlying mechanism remains to be elucidated. As hippocampal autophagy and primary cilia play a crucial role in learning and memory abilities, this study aimed to investigate the effects of AMA on hippocampal autophagy and primary cilia, and to explore their relationship with the changes of LKB1/AMPK signaling pathway in offspring rats. The whole brains and hippocampus of offspring born to 12-month-old (AMA) and 3-month-old (control) Sprague-Dawley (SD) female rats were collected on post-natal days (P) 14, 28, and 60. Transmission electron microscopy was employed to count the number of autophagosomes. The quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blotting were used to quantify gene expression, and immunofluorescence was used to measure primary cilia. The results revealed that autophagic activity was inhibited from childhood to adulthood in the AMA group. Furthermore, in the early developmental stage, primary ciliogenesis and growth in the hippocampus in the AMA group were impaired, with astrocytes being more severely affected. In addition, the AMA group exhibited an abnormal activation of the LKB1/AMPK signaling pathway. Thus, in offspring born to mothers of AMA, impaired hippocampal primary ciliary function and aberrant activation of the LKB1/AMPK signaling pathway are associated with inhibited autophagic activity.

The effect of Naringin on cognitive function, oxidative stress, cholinergic activity, CREB/BDNF signaling and hippocampal cell damage in offspring rats with utero-placental insufficiency-induced intrauterine growth restriction.

Intrauterine growth restriction (IUGR) induced by utero-placental insufficiency (UPI) results in delayed neural development and impaired brain growth. This study investigates the effects of Naringin (Nar) on memory, learning, cholinergic activity, oxidative stress markers, hippocampal CREB/BDNF signal pathway and cell damage in offspring of rats exposed to UPI. Twenty pregnant Wistar rats were randomly assigned to four groups: control, sham surgery, UPI+NS (UPI + normal saline as a vehicle), and UPI+Nar (UPI + Nar at 100mg/kg/day). UPI was induced by permanently occluding the uterine anterior vessels on embryonic day (ED) 18. Naringin or saline was administered orally from ED15 to ED21. Behavioral assessments of offspring, including working memory, avoidance learning, and anxiety-like behavior, were conducted on a postnatal day (PND) 21. Subsequently, hippocampal acetylcholinesterase (AChE) activity, catalase (CAT), superoxide dismutase (SOD), total antioxidant capacity (TAC), malondialdehyde (MDA), hippocampal transcript level of cyclic AMP response element-binding protein (CREB) and brain derived neurotrophic factor (BDNF) and apoptotic neuron density in the hippocampus were evaluated. Naringin-treated rats demonstrated significant improvements in working and avoidance memory, increases in CAT, SOD, and TAC, CREB, BDNF and reductions in AChE activity, MDA levels, apoptotic neuron density, and anxiety-like behaviors compared to the UPI+NS group (p<0.05). Naringin mitigates hippocampal cell damage, cognitive impairments, and anxiety by enhancing antioxidant defenses, modulating cholinergic activity and CREB/BDNF signaling in the brains of UPI-exposed offspring.

A high seizure burden increases brain concentrations of specialized pro-resolving mediators in the Scn1a+/- mouse model of Dravet syndrome.

Dravet syndrome is a severe, intractable epilepsy in which 80 % of patients have a de novo mutation in the gene SCN1A. We recently reported that a high seizure burden increased hippocampal concentrations of an array of pro-inflammatory prostaglandins in the Scn1a+/- mouse model of Dravet syndrome. This raised the possibility that a high seizure burden might also trigger the accumulation of specialized pro-resolving mediators that facilitate the resolution of neuroinflammation and brain repair. The present study therefore aimed to examine whether a high seizure burden increased hippocampal concentrations of various specialized pro-resolving mediators in the Scn1a+/- mouse model of Dravet syndrome. Scn1a+/- mice at postnatal day 21 (P21) were primed with a single hyperthermia-induced seizure event to induce a high seizure burden. On P24 primed Scn1a+/- mice with a high seizure burden, unprimed naïve Scn1a+/- mice and wild-type (WT) mice were euthanized and hippocampal tissue was collected for analysis of various specialized pro-resolving mediators using liquid chromatography mass spectrometry. Scn1a+/- mice with a high seizure burden showed increased hippocampal concentrations of the pro-inflammatory leukotrienes B4 and E4. Further, a high seizure burden increased hippocampal concentrations of various special pro-resolving mediators, including the maresins (maresin1), D-series resolvins (RVD1 and RVD4), and protectin (PCTR1). To further characterize these changes, we determined the mRNA expression of lipoxygenase genes, as these synthetic enzymes are common across classes of specialized pro-resolving mediators. However, hippocampal expression of Alox5, Alox12 and Alox15 were not influenced by a high seizure burden. We report for the first time that a high seizure burden increases the hippocampal concentrations of various specialized pro-resolving mediators in Scn1a+/- mice. This provides a platform for future studies to examine whether modulation of these mediators might be exploited to reduce seizures and facilitate brain repair in intractable epilepsy syndromes.