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Involvement of the brain renin-angiotensin system in the effects of maternal separation

ABSTRACT: The postnatal development of the mouse is characterized by a stress hyporesponsive period (SHRP), where basal corticosterone levels are low and responsiveness to mild stressors is reduced. Maternal separation is able to disrupt the SHRP and is widely used to model early trauma. In this study we aimed at identifying of brain systems involved in acute and possible long-term effects of maternal separation. We conducted a microarray-based gene expression analysis in the hypothalamic paraventricular nucleus after maternal separation, which revealed 52 differently regulated genes compared to undisturbed controls, among them are 37 up-regulated and 15 down-regulated genes. One of the prominently unregulated genes, angiotensinogen, was validated using a in-situ hybridization. Angiotensinogen is the precursor of angiotensin II the main effector of the brain renin-angiotensin system (RAS), which is known to be involved in stress system modulation in adult animals. Using the selective angiotensin type I receptor (AT(1)) antagonist candesartan we found strong effects on CRH and GR mRNA expression in the brain and ACTH release following maternal separation. AT(1) receptor blockade appears to enhance central effects of maternal separation in the neonate, suggesting a suppressing function of brain RAS during the SHRP. Taken together, our results illustrate the molecular adaptations that occur in the paraventricular nucleus following maternal separation and identify signaling cascades, that control stress system activity in the neonate. Keywords: phenotype

ORGANISM(S): Mus musculus

PROVIDER: GSE14687 | GEO | 2009/07/22

SECONDARY ACCESSION(S): PRJNA111675

REPOSITORIES: GEO

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Project description:Hypertension and persistent activation of the renin-angiotensin system (RAS) are predisposing factors for development of acute kidney injury (AKI). Although bone marrow-derived stromal cells (BMSCs) have shown therapeutic promise in treatment of AKI, the impact of pathological RAS on BMSC functionality has remained unresolved. RAS and its local components in the bone marrow are involved in several key steps of cell maturation processes. This may also render BMSC population vulnerable to alterations even in the early phases of RAS pathology. We isolated TG-BMSCs from young, end organ disease-free rats with increased RAS activation (human angiotensinogen/renin double transgenic rats; dTGR) that eventually develop hypertension and die of end-organ damage and kidney failure at 8-weeks-of-age. Control cells were isolated from wild-type Sprague-Dawley rats (SD-BMSCs). Cell phenotype, mitochondrial reactive oxygen species (ROS) production and respiration were assessed, and gene expression profiling was carried out using microarrays. Cells’ therapeutic efficacy was evaluated in a rat model of acute ischemia-reperfusion-induced AKI. Serum urea and creatinine were measured at 24h and 48h. Acute tubular damage was scored and immunohistochemistry was used for evaluation for markers of inflammation (MCP-1, ED-1), and kidney injury (KIM-1, NGAL). TG-BMSCs showed distinct mitochondrial morphology, decreased cell respiration, and increased production of ROS. Gene expression profiling revealed a pronounced pro-inflammatory phenotype. In contrast to the therapeutic effect of SD-BMSCs, administration of TG-BMSCs in the AKI model resulted in exacerbation of kidney injury and high mortality. Our results demonstrate that early persistent RAS activation can dramatically compromise therapeutic potential of BMSCs by shift into a pro-inflammatory phenotype with mitochondrial dysfunction. A comparison of transcriptome of a bone marrow-derived stromal cells from a double-transgene rats compared to those from control rats

Project description:Fetal alcohol spectrum disorder (FASD) is a common developmental behavioral disorder caused by maternal drinking during pregnancy. Children born with FASD often face additional stress, particularly maternal separation that adds yet additional deficits. The mechanism associated with this phenomenon is not known. Using a mouse model, prenatal ethanol exposure and maternal separation stress have resulted in behavioral deficits and the combination of treatments results in more than additive effects. In addition, behavioral alterations are associated with changes in hippocampal gene expression that persist into adulthood. What initiates and maintains these changes remains to be established and forms the focus of this research. Specifically, MeDIP-Seq was used to assess how changes in promoter DNA methylation are affected by the combination of prenatal ethanol exposure and maternal separation stress with the potential to affect gene expression. The novel results show different sets of genes implicated by promoter DNA methylation affected by both treatments independently, and a relatively unique set of genes affected by the combination of treatments. Prenatal ethanol exposure leads to altered promoter DNA methylation at genes important for brain function and transcriptional regulation. Maternal separation stress leads to changes at genes important for histone methylation and immune response, and the combination of two treatments results in DNA methylation changes at genes important for neuronal migration and immune response. Our dual results on gene expression and DNA methylation from the same samples have allowed comparison of the two observations. There is minimal reciprocal overlap between changes in promoter DNA methylation and gene expression, although overlapping genes tend to be critical for brain development and function. These results suggest that epigenetic mechanisms beyond promoter DNA methylation must be involved in lasting gene expression alterations leading to behavioral deficits implicated in FASD.

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Involvement of the brain renin-angiotensin system in the effects of maternal separation

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