The Absence of TLR4 Prevents Fetal Brain Injury in the Setting of Intrauterine Inflammation.

BACKGROUND: Exposure to intrauterine inflammation during pregnancy is linked to brain injury and neurobehavioral disorders in affected children. Innate immunity, specifically Toll-like receptor (TLR) signaling pathways are present throughout the reproductive tract as well as in the placenta, fetal membranes, and fetus. The TLR pathways are mechanistically involved in host responses to foreign pathogens and may lead to brain injury associated with prenatal inflammation. OBJECTIVE: We aimed to determine whether the activation of the TLR4 signaling pathway, in the mother and fetus, is critical to fetal brain injury in the setting of intrauterine inflammation. METHODS: A mini-laparotomy was performed on time pregnant C57B6 mice and 2 knockout mouse strains lacking the function of the Tlr4 and Myd88 genes on embryonic day 15. Intrauterine injections of Escherichia coli lipopolysaccharide or saline were administered as described previously. Dams were killed 6 hours postsurgery, and placental, amniotic fluid, and fetal brain tissue were collected. To assess brain injury, quantitative polymerase chain reaction (qPCR) analysis was performed on multiple components of the NOTCH signaling pathway, including Hes genes. Interleukin (IL) IL6, IL1ß, and CCL5 expression was assessed using qPCR and enzyme-linked immunosorbent assay. RESULTS: Using an established mouse model of intrauterine inflammation, we demonstrate that the abrogation of TLR4 signaling eliminates the cytokine response in mother and fetus and prevents brain injury associated with increased expression of transcriptional effectors of the NOTCH signaling pathway, Hes1 and Hes5. CONCLUSIONS: These data show that the activation of the TLR4 signaling pathway is necessary for the development of fetal brain injury in response to intrauterine inflammation.

Exposure to intrauterine inflammation alters metabolomic profiles in the amniotic fluid, fetal and neonatal brain in the mouse.

INTRODUCTION: Exposure to prenatal inflammation is associated with diverse adverse neurobehavioral outcomes in exposed offspring. The mechanism by which inflammation negatively impacts the developing brain is poorly understood. Metabolomic profiling provides an opportunity to identify specific metabolites, and novel pathways, which may reveal mechanisms by which exposure to intrauterine inflammation promotes fetal and neonatal brain injury. Therefore, we investigated whether exposure to intrauterine inflammation altered the metabolome of the amniotic fluid, fetal and neonatal brain. Additionally, we explored whether changes in the metabolomic profile from exposure to prenatal inflammation occurs in a sex-specific manner in the neonatal brain. METHODS: CD-1, timed pregnant mice received an intrauterine injection of lipopolysaccharide (50 µg/dam) or saline on embryonic day 15. Six and 48 hours later mice were sacrificed and amniotic fluid, and fetal brains were collected (n = 8/group). Postnatal brains were collected on day of life 1 (n = 6/group/sex). Global biochemical profiles were determined using ultra performance liquid chromatography/tandem mass spectrometry (Metabolon Inc.). Statistical analyses were performed by comparing samples from lipopolysaccharide and saline treated animals at each time point. For the P1 brains, analyses were stratified by sex. RESULTS/CONCLUSIONS: Exposure to intrauterine inflammation induced unique, temporally regulated changes in the metabolic profiles of amniotic fluid, fetal brain and postnatal brain. Six hours after exposure to intrauterine inflammation, the amniotic fluid and the fetal brain metabolomes were dramatically altered with significant enhancements of amino acid and purine metabolites. The amniotic fluid had enhanced levels of several members of the (hypo) xanthine pathway and this compound was validated as a potential biomarker. By 48 hours, the number of altered biochemicals in both the fetal brain and the amniotic fluid had declined, yet unique profiles existed. Neonatal pups exposed to intrauterine inflammation have significant alterations in their lipid metabolites, in particular, fatty acids. These sex-specific metabolic changes within the newborn brain offer an explanation regarding the sexual dimorphism of certain psychiatric and neurobehavioral disorders associated with exposure to prenatal inflammation.

Day-night cycles and the sleep-promoting factor, Sleepless, affect stem cell activity in the Drosophila testis.

Adult stem cells maintain tissue integrity and function by renewing cellular content of the organism through regulated mitotic divisions. Previous studies showed that stem cell activity is affected by local, systemic, and environmental cues. Here, we explore a role of environmental day-night cycles in modulating cell cycle progression in populations of adult stem cells. Using a classic stem cell system, the Drosophila spermatogonial stem cell niche, we reveal daily rhythms in division frequencies of germ-line and somatic stem cells that act cooperatively to produce male gametes. We also examine whether behavioral sleep-wake cycles, which are driven by the environmental day-night cycles, regulate stem cell function. We find that flies lacking the sleep-promoting factor Sleepless, which maintains normal sleep in Drosophila, have increased germ-line stem cell (GSC) division rates, and this effect is mediated, in part, through a GABAergic signaling pathway. We suggest that alterations in sleep can influence the daily dynamics of GSC divisions.