Offspring Brain Research Articles

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COVER IMAGE: Use Fig. 1 from CEP12663 Epigenetic regulations in kidney disease Smoking on offspring brain and kidney UPR in ipsilateral thalamus of brain infarct Aspirin against depressive behavior

Effect of Gestational Intake of Fisetin (3,3',4',7-Tetrahydroxyflavone) on Developmental Methyl Mercury Neurotoxicity in F1 Generation Rats.

Methyl mercury (MeHg) is a developmental neurotoxin that causes irreversible cognitive damage in offspring of gestationally exposed mothers. Currently, no preventive drugs are established against MeHg developmental neurotoxicity. The neuroprotective effect of gestational administration of a flavanoid against in utero toxicity of MeHg is not explored much. Hence, the present study validated the effect of a bioactive flavanoid, fisetin, on MeHg developmental neurotoxicity outcomes in rat offspring at postnatal weaning age. Pregnant Wistar rats were simultaneously given MeHg (1.5mg/kg b.w.) and two doses of fisetin (10 and 50mg/kg b.w. in two separate groups) orally from gestational day (GD) 5 till parturition. Accordingly, after parturition, on postnatal day (PND) 24, weaning F1 generation rats were studied for motor and cognitive behavioural changes. Biochemical and histopathological changes were also studied in the cerebral cortex, cerebellum and hippocampus on PND 25. Administration of fisetin during pregnancy prevented behavioural impairment due to transplacental MeHg exposure in weaning rats. Fisetin decreased the levels of oxidative stress markers, increased enzymatic and non-enzymatic antioxidant levels and increased the activity of membrane-bound ATPases and cholinergic function in F1 generation rats. In light microscopic studies, fisetin treatment protected the specific offspring brain regions from significant morphological aberrations. Between the two doses of fisetin studied, 10mg/kg b.w. was found to be more satisfactory and effective than 50mg/kg b.w. The present study shows that intake of fisetin during pregnancy in rats ameliorated in utero MeHg exposure-induced neurotoxicity outcomes in postnatal weaning F1 generation rats.

Exposure to a Highly Caloric Palatable Diet during the Perinatal Period Affects the Expression of the Endogenous Cannabinoid System in the Brain, Liver and Adipose Tissue of Adult Rat Offspring.

Recent studies have linked gestational exposure to highly caloric diets with a disrupted endogenous cannabinoid system (ECS). In the present study, we have extended these studies by analyzing the impact of the exposure to a palatable diet during gestation and lactation on a) the adult expression of endocannabinoid-related behaviors, b) the metabolic profile of adult offspring and c) the mRNA expression of the signaling machinery of the ECS in the hypothalamus, the liver and the adipose tissue of adult offspring of both sexes. Exposure to a palatable diet resulted in a) sex-dimorphic and perinatal diet specific feeding behaviors, including the differential response to the inhibitory effects of the cannabinoid receptor inverse agonist AM251, b) features of metabolic syndrome including increased adiposity, hyperleptinemia, hypertriglyceridemia and hypercholesterolemia and c) tissue and sex-specific changes in the expression of both CB1 and CB2 receptors and in that of the endocannabinoid-degrading enzymes FAAH and MAGL, being the adipose tissue the most affected organ analyzed. Since the effects were observed in adult animals that were weaned while consuming a normal diet, the present results indicate that the ECS is one of the targets of maternal programming of the offspring energy expenditure. These results clearly indicate that the maternal diet has long-term effects on the development of pups through multiple alterations of signaling homeostatic pathways that include the ECS. The potential relevance of these alterations for the current obesity epidemic is discussed.

Early micronutrient supplementation protects against early stress-induced cognitive impairments.

Early-life stress (ES) impairs cognition later in life. Because ES prevention is problematic, intervention is needed, yet the mechanisms that underlie ES remain largely unknown. So far, the role of early nutrition in brain programming has been largely ignored. Here, we demonstrate that essential 1-carbon metabolism-associated micronutrients (1-CMAMs; i.e., methionine and B vitamins) early in life are crucial in programming later cognition by ES. ES was induced in male C57Bl/6 mice from postnatal d (P)2-9. 1-CMAM levels were measured centrally and peripherally by using liquid chromatography-mass spectroscopy. Next, we supplemented the maternal diet with 1-CMAM only during the ES period and studied cognitive, neuroendocrine, neurogenic, transcriptional, and epigenetic changes in adult offspring. We demonstrate that ES specifically reduces methionine in offspring plasma and brain. Of note, dietary 1-CMAM enrichment during P2-9 restored methionine levels and rescued ES-induced adult cognitive impairments. Beneficial effects of this early dietary enrichment were associated with prevention of the ES-induced rise in corticosterone and adrenal gland hypertrophy did not involve changes in maternal care, hippocampal volume, neurogenesis, or global/Nr3c1-specific DNA methylation. In summary, nutrition is important in brain programming by ES. A short, early supplementation with essential micronutrients can already prevent lasting effects of ES. This concept opens new avenues for nutritional intervention.-Naninck, E. F. G., Oosterink, J. E., Yam, K.-Y., de Vries, L. P., Schierbeek, H., van Goudoever, J. B., Verkaik-Schakel, R.-N., Plantinga, J. A., Plosch, T., Lucassen, P. J., Korosi, A. Early micronutrient supplementation protects against early stress-induced cognitive impairments.

Maternal immune activation transgenerationally modulates maternal care and offspring depression-like behavior

Gestational infection is increasingly being recognized for its involvement as causative mechanism in severe developmental brain abnormalities and its contribution to the pathogenesis of psychopathologies later in life. First observations in the widely accepted maternal immune activation (MIA) model based upon the systemic administration of the viral mimetic Polyinosinic:polycytidylic acid (poly(I:C)) have recently suggested a transmission of behavioral and transcriptional traits across generations. Although maternal care behavior (MCB) is known as essential mediator of the transgenerational effects of environmental challenges on offspring brain function and behavior, the possible propagation of alterations of MCB resulting from MIA to following generations has not yet been examined. Here we show that poly(I:C) stimulation at embryonic day 12.5 (E12.5) leads to aberrant MCB and that this effect is transmitted to the female F1 offspring. The transgenerational effects on MCB are paralleled by enhanced depression-like behavior in the second generation F2 offspring with contributions of both maternal and paternal heritages. Examination of offspring hippocampal expression of genes known as targets of MCB and relevant for ensuing non-genetic transmission of altered brain function and behavior revealed transgenerationally conserved and modified expressional patterns in the F1 and F2 generation.Collectively these data firstly demonstrate the transgenerational transmission of the impact of gestational immune activation on the reproductive care behavior of the mother. Behavioral and molecular characteristics of first and second generation offspring suggest transgenerationally imprinted consequences of gestational infection on psychopathological traits related to mood disorders which remain to be examined in future cross-fostering experiments.

Maternal obesity increases inflammation and exacerbates damage following neonatal hypoxic-ischaemic brain injury in rats

ObjectiveIn humans, maternal obesity is associated with an increase in the incidence of birth related difficulties. However, the impact of maternal obesity on the severity of brain injury in offspring is not known. Recent studies have found evidence of increased glial response and inflammatory mediators in the brains as a result of obesity in humans and rodents. We hypothesised that hypoxic-ischaemic (HI) brain injury is greater in neonatal offspring from obese rat mothers compared to lean controls. MethodsFemale Sprague Dawley rats were randomly allocated to high fat (HFD, n=8) or chow (n=4) diet and mated with lean male rats. On postnatal day 7 (P7), male and female pups were randomly assigned to HI injury or control (C) groups. HI injury was induced by occlusion of the right carotid artery followed by 3h exposure to 8% oxygen, at 37°C. Control pups were removed from the mother for the same duration under ambient conditions. Righting behaviour was measured on day 1 and 7 following HI. The extent of brain injury was quantified in brain sections from P14 pups using cresyl violet staining and the difference in volume between brain hemispheres was measured. ResultsBefore mating, HFD mothers were 11% heavier than Chow mothers (p<0.05, t-test). Righting reflex was delayed in offspring from HFD-fed mothers compared to the Chow mothers. The Chow-HI pups showed a loss in ipsilateral brain tissue, while the HFD-HI group had significantly greater loss. No significant difference was detected in brain volume between the HFD-C and Chow-C pups. When analysed on a per litter basis, the size of the injury was significantly correlated with maternal weight. Similar observations were made with neuronal staining showing a greater loss of neurons in the brain of offspring from HFD-mothers following HI compared to Chow. Astrocytes appeared to more hypertrophic and a greater number of microglia were present in the injured hemisphere in offspring from mothers on HFD. HI caused an increase in the proportion of amoeboid microglia and exposure to maternal HFD exacerbated this response. In the contralateral hemisphere, offspring exposed to maternal HFD displayed a reduced proportion of ramified microglia. ConclusionsOur data clearly demonstrate that maternal obesity can exacerbate the severity of brain damage caused by HI in neonatal offspring. Given that previous studies have shown enhanced inflammatory responses in offspring of obese mothers, these factors including gliosis and microglial infiltration are likely to contribute to enhanced brain injury.

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.

Differences in brain functional connectivity at resting state in neonates born to healthy obese or normal-weight mothers.

Recent studies have shown associations between maternal obesity at pre- or early pregnancy and long-term neurodevelopment in children, suggesting in utero effects of maternal obesity on offspring brain development. In this study, we examined whether brain functional connectivity to the prefrontal lobe network is different in newborns from normal-weight or obese mothers. Thirty-four full-term healthy infants from uncomplicated pregnancies were included, with 18 born to normal-weight and 16 born to obese mothers. Two weeks after delivery, the infants underwent an magnetic resonance imaging (MRI) examination during natural sleep, which included structural imaging and resting-state functional MRI (fMRI) scans. Independent component analysis was used to identify the prefrontal lobe network, and dual regression was used to compare functional connectivity between groups. Infants born to normal-weight mothers had higher recruiting (P<0.05, corrected) of dorsal anterior cingulate cortex regions to the prefrontal network after adjusting for maternal intelligence quotient, gestational weight gain and infant postmenstrual age, gender, birth weight/length, head circumference and neonatal diet. The functional connectivity strength in dorsal anterior cingulate cortex negatively correlated (P<0.05) with maternal fat mass percentage measured at early pregnancy. This preliminary study indicates that exposure to maternal obesity in utero may be associated with changes in resting-state functional connectivity in the newborn offspring's brain.

Maternal stress has divergent effects on gene expression patterns in the brains of male and female threespine stickleback.

Maternal stress can have long-term effects on neurodevelopment that can influence offspring performance and population evolutionary trajectories. To examine the mechanistic basis for these neurodevelopmental effects of maternal stress, we used RNA-seq to assess differential gene expression across the brain transcriptome of adult male and female threespine stickleback (Gasterosteus aculeatus) from stressed and unstressed mothers. We identified sexually divergent effects of maternal stress on the brain transcriptome. In males, genes that were upregulated by maternal stress were enriched for processes involved in synaptic function and organization and steroid hormone-mediated signalling pathways, whereas in females genes that were upregulated by maternal stress were enriched for processes involved in protein translation and metabolic functions. The expression of several genes involved in the hypothalamic-pituitary-interrenal response to stress and epigenetic processes such as the regulation of DNA methylation patterns and miRNAs increased in males and not in females. These data suggest that maternal stress has markedly different effects on cellular pathways in the brains of male and female offspring of mothers that are exposed to stress, which could have important implications when assessing the long-term ecological and evolutionary impacts of stress across generations.

Relationship between maternal environment and DNA methylation patterns of estrogen receptor alpha in wild Eastern Bluebird (Sialia sialis) nestlings: a pilot study.

There is mounting evidence that, across taxa, females breeding in competitive environments tend to allocate more testosterone to their offspring prenatally and these offspring typically have more aggressive and faster‐growing phenotypes. To date, no study has determined the mechanisms mediating this maternal effect's influence on offspring phenotype. However, levels of estrogen receptor alpha (ER α) gene expression are linked to differences in early growth and aggression; thus, maternal hormones may alter gene regulation, perhaps via DNA methylation, of ER α in offspring during prenatal development. We performed a pilot study to examine natural variation in testosterone allocation to offspring through egg yolks in wild Eastern Bluebirds (Sialia sialis) in varying breeding densities and percent DNA methylation of CG dinucleotides in the ER α promoter in offspring brain regions associated with growth and behavior. We hypothesized that breeding density would be positively correlated with yolk testosterone, and prenatal exposure to maternal‐derived yolk testosterone would be associated with greater offspring growth and decreased ER α promoter methylation. Yolk testosterone concentration was positively correlated with breeding density, nestling growth rate, and percent DNA methylation of one out of five investigated CpG sites (site 3) in the diencephalon ER α promoter, but none in the telencephalon (n = 10). Percent DNA methylation of diencephalon CpG site 3 was positively correlated with growth rate. These data suggest a possible role for epigenetics in mediating the effects of the maternal environment on offspring phenotype. Experimentally examining this mechanism with a larger sample size in future studies may help elucidate a prominent way in which animals respond to their environment. Further, by determining the mechanisms that mediate maternal effects, we can begin to understand the potential for the heritability of these mechanisms and the impact that maternal effects are capable of producing at an evolutionary scale.

Peri-Implantation Hormonal Milieu: Elucidating Mechanisms of Adverse Neurodevelopmental Outcomes.

While live births resulting from assisted reproductive technology (ART) exceed 1% of total births annually, the effect of ART on fetal development is not well understood. Data have demonstrated that IVF leads to alterations in DNA methylation and gene expression in the placenta that may have long-term effects on health and disease. Studies have linked adverse neurodevelopmental outcomes to ART, although human studies are inconclusive. In order to isolate the peri-implantation environment and its effects on brain development, we utilized a mouse model with and without superovulation and examined the effect of adult behavior as well as adult cortical neuronal density. Adult offspring of superovulated dams showed increased anxiety-like behavior compared to offspring of naturally mated dams (P < .05). There was no difference in memory and learning tests between the 2 groups. The adult brains from offspring of superovulated recipients had fewer neurons per field compared to naturally mated control offspring (P < .05). In order to examine potential pathways leading to these changes, we measured messenger RNA and microRNA (miRNA) expression in fetal brains at E18.5. Microarray analysis found that miRNAs miR-122, miR-144, and miR-211, involved in regulation of neuronal migration and differentiation, were downregulated in brains of offspring exposed to a superovulated environment(P < .05). There was also altered expression of genes involved in neuronal development. These results suggest that the peri-implantation environment can affect neurodevelopment and can lead to behavioral changes in adulthood. Human studies with long-term follow-up of children from ART are necessary to further investigate the influence of ART on the offspring.

A sexually dichotomous, autistic-like phenotype is induced by Group B Streptococcus maternofetal immune activation.

Group B Streptococcus (GBS) is a commensal bacterium present in the lower genital tract of 15-30% of healthy pregnant women. GBS is the leading cause of chorioamnionitis and cerebral injuries in newborns, occurring most often in the absence of maternofetal pathogen translocation. Despite GBS being the most frequent bacterium colonizing pregnant women, no preclinical studies have investigated the impact of end-gestational maternal GBS exposure on the offspring's brain development and its behavioral correlates. Our hypothesis is that GBS-induced gestational infection/inflammation has a deleterious neurodevelopmental impact on uninfected offspring. Our goal was to study the impact of maternal GBS infection on the placental and neurodevelopmental features in the offspring using a new preclinical rat model. GBS-exposed placentas exhibited chorioamnionitis characterized by the presence of Gram-positive cocci and polymorphonuclear cells, with the latter being significantly more prominent in the labyrinth of male offspring. GBS-exposed male offspring had reduced thickness of periventricular white matter. In addition, they exhibited autistic-like behaviors, such as abnormal social interaction and communication, impaired processing of sensory information and hyperactivity. Overall, these data show for the first time that gestational exposure to GBS plays an important role in the generation of neurodevelopmental abnormalities reminiscent of human autism spectrum disorders (ASD). These results provide new evidence in favor of the role of a common and modifiable infectious/inflammatory environmental factor in human ASD pathophysiology. Autism Res 2017, 10: 233-245. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Reducing dietary intake of linoleic acid of mouse dams during lactation increases offspring brain n-3 LCPUFA content

Omega (n-)3 and n-6 long chain polyunsaturated fatty acids (LCPUFA) accumulation in the infant brain after birth is strongly driven by dietary supply of n-3 and n-6 LCPUFAs and their C18 precursors through breast milk or infant formula. n-3 LCPUFA accretion is associated with positive effects on neurodevelopmental outcome whereas high n-6 LCPUFA accumulation is considered disadvantageous. Maternal diet is crucial for breast milk fatty acid composition. Unfortunately, global increases in linoleic acid (C18:2n-6; LA) intake have dramatically increased n-6 LCPUFA and reduced n-3 LCPUFA availability for breastfed infants. We investigated the effects of reducing maternal dietary LA, or increasing n-3 LCPUFA, during lactation on milk and offspring brain fatty acids in mice. Offspring brain n-3 LCPUFA was higher following both interventions, although effects were mediated by different mechanisms. Because of competitive interactions between n-3 and n-6 fatty acids, lowering maternal LA intake may support neurodevelopment in breastfed infants.

Beneficial effect of feeding a ketogenic diet to mothers on brain development in their progeny with a murine model of pyruvate dehydrogenase complex deficiency

Pyruvate dehydrogenase complex (PDC) deficiency is a major inborn error of oxidative metabolism of pyruvate in the mitochondria causing congenital lactic acidosis and primarily structural and functional abnormalities of the central nervous system. To provide an alternate source of acetyl-CoA derived from ketone bodies to the developing brain, a formula high in fat content is widely employed as a treatment. In the present study we investigated efficacy of a high-fat diet given to mothers during pregnancy and lactation on lessening of the impact of PDC deficiency on brain development in PDC-deficient female progeny. MethodsA murine model of systemic PDC deficiency by interrupting the X-linked Pdha1 gene was employed in this study. ResultsMaternal consumption of a high-fat diet during pregnancy and lactation had no effect on number of live-birth, body growth, tissue PDC activity levels, as well as the in vitro rates of glucose oxidation and fatty acid biosynthesis by the developing brain of PDC-deficient female offspring during the postnatal age 35days, as compared to the PDC-deficient progeny born to dams on a chow diet. Interestingly, brain weight was normalized in PDC-deficient progeny of high fat-fed mothers with improvement in impairment in brain structure deficit whereas brain weight was significantly decreased and was associated with greater cerebral structural defects in progeny of chow-fed mothers as compared to control progeny of mothers fed either a chow or high fat diet. ConclusionThe findings provide for the first time experimental support for beneficial effects of a ketogenic diet during the prenatal and early postnatal periods on the brain development of PDC-deficient mammalian progeny.

Maternal consumption of a diet lacking omega‐3 fatty acids during development alters pup behavior and brain metabolism later in life

Rodent models have shown a relationship between omega‐3 fatty acid (n‐3FA) consumption and offspring behaviors related to anxiety, depression, and cognition. In these studies, offspring n‐3FA deficiency or supplementation continued after weaning, obscuring phenomena due solely to the developmental effects of maternal consumption of n‐3FAs during pregnancy and lactation. Our objective was to develop a rat model that allowed us to isolate the effects of gestational and perinatal n‐3FA deficiency and supplementation on offspring behavior and brain metabolic capacity. Female rats were fed diets formulated with 7% sunflower (−n‐3FA) or menhaden fish oil (+n‐3FA) for two cycles of gestation and lactation. Rat pups from the second reproductive cycle were weaned onto the animal facility diet, containing recommended n‐3FA levels, for five weeks prior to behavioral assessment and brain removal. Pups were tested in the open field (OF), forced swim (FS) and the holeboard (HB) tests to examine behaviors related to novelty reactivity and seeking, depression, and learning and memory, respectively. Brain metabolic capacity was assessed by quantitative cytochrome oxidase (CO) histochemistry. Maternal n‐3FA consumption did not affect behavior in the FS and HB tests. A diet x day interaction was observed in the OF test [F(1,16) = 4.625, P = 0.047]. Pups born to dams lacking n‐3FAs exhibited increased total ambulatory time (73.9 +/− 6.7 seconds) in the novel OF environment on day 1 when compared to pups whose dams consumed diets with n‐3FA (55.2 +/− 5.9 seconds). But the amount of ambulatory time in the familiar OF environment on day 2 was the same. Increased time spent moving in a novel (but not in a familiar) environment may indicate increased novelty reactivity. Pups in the –n‐3FA group spent more time in the center of the OF on both days than pups in the +n‐3FA group [F(1,16) = 5.829, P = 0.028], suggesting an increase in novelty‐seeking or risk‐taking behavior, as rats normally avoid the center of the OF. Maternal n‐3FA deficiency significantly decreased CO activity in the offspring's posterior cingulate cortex (P= 0.03), a cortical component of the limbic system involved in emotional behavior. There were also trends (P = 0.05) for increased CO activity in the nucleus accumbens shell and decreased CO activity in the cortical nucleus of the amygdala. These brain regions are often associated with emotional memories, reward‐seeking, defensive behavior and fear, respectively. We hypothesize that the increased ambulatory time exhibited by pups born to n‐3FA deficient mothers may be due to the decreased metabolism of the posterior cingulate cortex and cortical amygdala, which could lead to risk‐taking responses to the new environment. Increased metabolism in the accumbens shell might have also contributed to greater reward‐seeking in the new environment. In conclusion, changes in the n‐3FA content of the maternal diet during gestation and lactation alone, without alterations in offspring diet, can affect offspring emotional behavior and brain metabolism.Support or Funding InformationSupport for this project came from the Texas State University Research Enhancement and Developmental Leave Programs for ML.

The effect of Iron Deficient Diets (with or without LC‐PUFA) on the Offspring Brain Lipid and Eicosanoid Metabolism during Pre‐Postnatal Development

ObjectivesWe previously found that an iron deficient diet (ID) devoid in long chain polyunsaturated fatty acids (LC‐PUFA, n‐6:n‐3=59:1) fed to pregnant and lactating guinea pigs resulted in a large spectrum of auditory alterations in the peripheral neurophysiology in the offspring. Unexpectedly, we found that adding physiological amount of LC‐PUFA (n‐6:n‐3=11:1) to this ID diet induced minor impairments. The aim of the present study was to evaluate the impact of the (ID) diets (with or without LC‐PUFA) on Δ6‐desaturase expression, COX II protein and prostaglandin levels in the brain of these pups.MethodsIn experiment 1, female guinea pigs were fed an iron sufficient (IS) or iron deficient (ID) diet devoid in LC‐PUFA during the gestation and lactation periods. In experiment 2, female guinea pigs were fed the IS or ID diet in the presence of physiological quantities of LC‐PUFA. After weaning, from postnatal day 9 (PNd9) onward, the IS and IS+LC‐PUFA diets were given to pups in experiment 1 and 2, respectively. Brains and other tissues were collected on PNd24.Summary of resultsIn both experiments, the brain COX II protein levels were unaffected in the ID and ID+LC‐PUFA siblings. In experiment 2, however, PGE2 brain concentrations were reduced in ID+LC‐PUFA compared to IS+LC‐PUFA pups. Similarly, the offspring born to dams fed the ID+LC‐PUFA diet also exhibited a trend for a reduced brain Δ6‐desaturase expression.ConclusionThese experiments are showing that the addition of LC‐PUFA to a diet know to induce a mild iron deficiency have an impact on specific markers of brain lipid‐eisosanoid metabolism. However, the physiological outcomes of these central nervous system changes are unknown.Support or Funding InformationFunded by the Canadian Institutes of Health Research

Prenatal Exposure to Arsenic Impairs Behavioral Flexibility and Cortical Structure in Mice.

Exposure to arsenic from well water in developing countries is suspected to cause developmental neurotoxicity. Although, it has been demonstrated that exposure to sodium arsenite (NaAsO2) suppresses neurite outgrowth of cortical neurons in vitro, it is largely unknown how developmental exposure to NaAsO2 impairs higher brain function and affects cortical histology. Here, we investigated the effect of prenatal NaAsO2 exposure on the behavior of mice in adulthood, and evaluated histological changes in the prelimbic cortex (PrL), which is a part of the medial prefrontal cortex that is critically involved in cognition. Drinking water with or without NaAsO2 (85 ppm) was provided to pregnant C3H mice from gestational days 8 to 18, and offspring of both sexes were subjected to cognitive behavioral analyses at 60 weeks of age. The brains of female offspring were subsequently harvested and used for morphometrical analyses. We found that both male and female mice prenatally exposed to NaAsO2 displayed an impaired adaptation to repetitive reversal tasks. In morphometrical analyses of Nissl- or Golgi-stained tissue sections, we found that NaAsO2 exposure was associated with a significant increase in the number of pyramidal neurons in layers V and VI of the PrL, but not other layers of the PrL. More strikingly, prenatal NaAsO2 exposure was associated with a significant decrease in neurite length but not dendrite spine density in all layers of the PrL. Taken together, our results indicate that prenatal exposure to NaAsO2 leads to behavioral inflexibility in adulthood and cortical disarrangement in the PrL might contribute to this behavioral impairment.

Prenatal fat exposure and hypothalamic PPAR β/δ: Possible relationship to increased neurogenesis of orexigenic peptide neurons

Gestational exposure to a fat-rich diet, while elevating maternal circulating fatty acids, increases in the offspring’s hypothalamus and amygdala the proliferation and density of neurons that express neuropeptides known to stimulate consummatory behavior. To understand the relationship between these phenomena, this study examined in the brain of postnatal offspring (day 15) the effect of prenatal fat exposure on the transcription factor, peroxisome proliferator-activated receptor (PPAR) β/δ, which is sensitive to fatty acids, and the relationship of PPAR β/δ to the orexigenic neuropeptides, orexin, melanin-concentrating hormone, and enkephalin. Prenatal exposure to a fat-rich diet compared to low-fat chow increased the density of cells immunoreactive for PPAR β/δ in the hypothalamic paraventricular nucleus (PVN), perifornical lateral hypothalamus (PFLH), and central nucleus of the amygdala (CeA), but not the hypothalamic arcuate nucleus or basolateral amygdaloid nucleus. It also increased co-labeling of PPAR β/δ with the cell proliferation marker, BrdU, or neuronal marker, NeuN, and the triple labeling of PPAR β/δ with BrdU plus NeuN, indicating an increase in proliferation and density of new PPAR β/δ neurons. Prenatal fat exposure stimulated the double-labeling of PPAR β/δ with orexin or melanin-concentrating hormone in the PFLH and enkephalin in the PVN and CeA and also triple-labeling of PPAR β/δ with BrdU and these neuropeptides, indicating that dietary fat increases the genesis of PPAR β/δ neurons that produce these peptides. These findings demonstrate a close anatomical relationship between PPAR β/δ and the increased proliferation and density of peptide-expressing neurons in the hypothalamus and amygdala of fat-exposed offspring.

Differential expression of astrocytic connexins in a mouse model of prenatal alcohol exposure

Maternal alcohol consumption during gestation can cause serious injury to the fetus, and may result in a range of physiological and behavioral impairments, including increased seizure susceptibility, that are collectively termed fetal alcohol spectrum disorder (FASD). The cellular mechanisms underlying increased seizure susceptibility in FASD are not well understood, but could involve altered excitatory coupling of neuronal populations mediated by gap junction proteins. We utilized a mouse model of the prenatal alcohol exposure (PAE) to study the expression pattern of connexin (Cx) major components of gap junctions, and pannexin proteins, which form membrane channels, in the brain of 2–3weeks old PAE and control postnatal offspring. PAE during the first trimester-equivalent period of pregnancy in mice resulted in significant up-regulation of Cx30 mRNA and Cx30 total protein in the hippocampus of PAE animals compared to age-matched controls. Surface level expression of both dimeric and monomeric Cx30 were also found to be significantly up-regulated in both hippocampus and cerebral cortex of PAE animals compared to age-matched controls. On the membrane surface, the fast migrating form of Cx43 was found to be up-regulated in the hippocampus of PAE mice. However, we did not see any up-regulation of the phosphorylated forms of Cx43 on the membrane surface. These results indicate that the expression and processing of astrocytic connexins (Cx30, Cx43) are up-regulated in the brain of PAE offspring, and these changes could play a role in the cerebral hyperexcitability observed in these animals.

Impact of prenatal polycyclic aromatic hydrocarbon exposure on behavior, cortical gene expression, and DNA methylation of the Bdnf gene

Prenatal exposure to polycyclic aromatic hydrocarbons (PAH) has been associated with sustained effects on the brain and behavior in offspring. However, the mechanisms have yet to be determined. We hypothesized that prenatal exposure to ambient PAH in mice would be associated with impaired neurocognition, increased anxiety, altered cortical expression of Bdnf and Grin2b, and greater DNA methylation of Bdnf. Our results indicated that during open-field testing, prenatal PAH–exposed offspring spent more time immobile and less time exploring. Females produced more fecal boli. Offspring prenatally exposed to PAH displayed modest reductions in overall exploration of objects. Further, prenatal PAH exposure was associated with lower cortical expression of Grin2b and Bdnf in males and greater Bdnf IV promoter methylation. Epigenetic differences within the Bdnf IV promoter correlated with Bdnf gene expression but not with the observed behavioral outcomes, suggesting that additional targets may account for these PAH-associated effects.