Browsing by Subject "Anemia"

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    Characterization of glycosylphoshatidylinositol-anchored ceruloplasmin in multiple redent organs following dietary copper deficiency.
    (2010-10) Mostad, Elise June
    Copper is a necessary metal cofactor in many enzymes that catalyze key reactions in both prokaryotes and eukaryotes. Ceruloplasmin (Cp) is a copper-dependent enzyme that acts as a ferroxidase, oxidizing FeII to FeIII for systemic iron mobilization. Cp is expressed as both a secreted plasma (sCp) enzyme and a membrane-bound glycosylphosphatidylinositol- anchored (GPI-Cp) splice variant enzyme. sCp is the most abundant copper-binding protein in mammalian plasma. The ferroxidase activity of Cp is essential for iron mobilization, as Cp null humans and mice exhibit selective tissue-specific iron overload. Dietary copper deficient (CuD) rodents have near total loss of Cp activity, severe loss of Cp protein, and anemia. The impacts of dietary copper deficiency on GPICp has not been previously evaluated. Studies were conducted in Holtzman and Sprague- Dawley rats, albino mice, and Cp -/- mice, to investigate the copper-iron interaction and further characterize GPI-Cp. Purified membrane extracts of these rodent tissues detected immunoreactive Cp protein, especially enriched in spleen and kidney, but not in membranes from Cp -/- mice. Immunoreactive Cp protein was released with phosphotidylinositol-specific phospholipase C treatment and released protein exhibited ferroxidase activity. These data suggest that the membrane-bound Cp immunoreactivity detected is GPI-anchored. Following perinatal and postnatal copper restriction, GPI-Cp was markedly lower in spleen and modestly lower in liver of CuD rats and mice, compared to copper-adequate (CuA) rodents. Livers of CuD mice contained elevated liver non-heme iron (NHI), while spleen NHI was lower in CuD than CuA rats, and not different in CuD mice, implying that lower GPI-Cp was not correlated with augmented NHI levels in CuD rodent spleens. Spleen and liver membranes of CuD rats expressed augmented levels of ferroportin, the iron efflux transporter, which may compensate for the loss of GPI-Cp in iron efflux. Copper deficient rats and mice both develop severe anemia but only in rats is plasma iron lower than normal, consistent with impaired Cp function. As multicopper oxidases like Cp are thought to be the major metabolic link between copper and iron, additional research is needed to determine the impact, if any, of lower GPI-Cp on iron flux and the development of anemia when copper is limiting.
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    The Effect of Developmental Iron Deficiency on Gene Expression, Tet Proteins, and Dna Hydroxymethylation In the Rodent Brain
    (2020-06) Barks, Amanda
    Fetal-neonatal iron deficiency (ID) has a lasting negative impact on neurodevelopment, resulting in significant cognitive, socio-emotional, and learning and memory deficits in adulthood, as well as increased risk for neuropsychiatric disease. Given that ID is the most common micronutrient deficiency worldwide, and that pregnant women and young children are disproportionately affected, it presents a significant public health concern. Preclinical models have demonstrated that the developing central nervous system (CNS) is particularly affected by ID, and that the deleterious neurodevelopmental effects and neuropsychiatric risks that follow are associated with dysregulation of CNS gene expression. Dysregulated genes map to signaling pathways and networks critical for neurodevelopment and neuronal function, suggesting that these critical functions are compromised by ID. If developmental ID is corrected by iron repletion within a critical period, correction of neurodevelopmental deficits is possible. However, if iron repletion occurs outside of the critical period, the phenotypic and gene expression changes persist into adulthood despite correction of the deficiency. While changes in gene expression can be understood as the proximate cause of the ID neurocognitive phenotype, it is still unclear what the ultimate cause is. As such, there is a gap in our understanding of how developmental ID establishes and maintains gene expression changes in the CNS. A potential mechanism by which iron could enact these changes is through Ten-Eleven Translocation (TET) enzymes, a family of iron-dependent hydroxylases that generate the epigenetic modification 5-hydroxymethylcytosine (5hmC), or DNA hydroxymethylation. Epigenetic modifications such as DNA hydroxymethylation have the ability to stably influence gene expression throughout the lifespan, and are known to be labile to environmental influences. Of particular relevance, 5hmC is more abundant in the brain than any other tissue, and it increases in enrichment as neurodevelopment progresses, particularly in genes critical for neuronal development and function. The central hypothesis of my thesis research is that dysregulation of TET enzymatic activity and 5hmC by fetal-neonatal ID drives gene expression changes in brain that contribute to the long-term neurocognitive phenotype of developmental ID. To test this hypothesis, the following aims were proposed: 1) Determine the effect of fetal-neonatal ID on TET activity and 5hmC in two regions of the developing rat brain, the hippocampus and the cerebellum, and 2) Determine whether treatment of developmental ID with dietary iron repletion can reverse the changes to this epigenetic system. Completion of these aims contributes to the long-term goal of understanding the cellular and molecular underpinnings of CNS dysfunction and increased neuropsychiatric disease risk following developmental ID. Because the standard therapy of iron repletion incompletely rescues the neurodevelopmental phenotype of ID, there is a need for better therapeutic options. By better understanding the underlying mechanisms of ID-related hippocampal dysfunction, it may be possible to identify new therapeutic targets for more effective treatment of iron deficiency.
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    The effects of iron deficiency on the developing brain vasculature
    (2016-10) Nguyen, Thu An
    Iron deficiency is amongst the most severe and important micronutrient deficiencies, affecting millions of people globally, especially pregnant women and young children. Particularly, iron deficiency anemia (IDA) adversely affects the cognitive performance, behavior and growth of infants, preschool and school-aged children. Recently it was demonstrated that iron deficiency (FeD) during gestational and early postnatal life, induces angiogenesis/vasculogenesis in the developing neonatal rat brain. Previously, the impacts of FeD on the developing brain were reported in postnatal rats. Although FeD and thyroid hormone disruption share similar brain development deficits, combined FeD and impaired thyroidal status did not alter the developing brain vasculature in neonatal rats. Hence, the altered vasculature is an important independent effect of FeD on the developing brain. In this study, I further demonstrated that the angiogenesis effect of FeD is evident since birth and continues into the postnatal stage. Moreover, previous research showed restoration of other aspects of FeD’s impacts on the neonatal rat brain with Fe repletion or supplementation. Therefore, I hypothesized that the angiogenesis effects in developing Fe deficient rat brains are reversible with Fe repletion. qPCR data showed an increase in brain mRNA level of endothelial cell marker genes and angiogenesis associated genes in the developing iron deficient rat brain compared to control at birth, postnatal days 7 and 14. FeD also increases vessel branch points suggesting the FeD induced angiogenesis occurs since birth in the neonatal rat brains. After iron repletion on postnatal day 7, mRNA level of the same genes and vessel branch points had no significant increase compared to control at postnatal day 14 and returned to approximately the same level as control at postnatal day 30. These results suggest that FeD induced angiogenesis could be reversible as evident by vessel regression upon iron repletion. Brain angiogenesis is critically regulated by hypoxia-inducible factor 1 (HIF1) which is activated during hypoxia. I hypothesized that neonatal FeD results in tissue hypoxia and activates hypoxia-inducible factor 1 alpha (HIF1α) leading to induction of expression of several genes associated with angiogenesis. Western blot densitometry indicated no significant difference in HIF1α expression in Fe deficient brains compared to control at postnatal day 7 and 14. Finally, since it is unknown whether the induced vasculature is beneficial or not to the Fe deficient developing brain, we also assessed mRNA level of an endothelial integrity marker, plasmalemmal vesicle- associated protein, PLVAP or PV-1 that was expressed in a fenestrated blood brain barrier. The mRNA level of PV-1 gene was not altered in both FeD and Fe repletion groups, however, PV-1 specific roles as a BBB integrity marker in the process of vessel sprouting remains to be determined. Overall, this study on the independent effects of FeD on the developing brain vasculature demonstrated reversibility of the induced blood vessels outgrowth with Fe repletion at postnatal day 7, however, it is unclear if hypoxic signaling through the HIF1 pathway via HIF1α activation contributes to brain angiogenesis due to FeD.