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Sterols and oxysterols in brain and the immune system. / Anna Meljon
Swansea University Author: Anna Meljon
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This project investigates sterol and oxysterol content of murine brain and macrophages. Oxysterols are oxidised forms of cholesterol implicated in a wide array of biological functions. The compounds were analysed with LC-MS LTQ-Orbitrap high resolution system, which provides a highly sensitive and a...
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This project investigates sterol and oxysterol content of murine brain and macrophages. Oxysterols are oxidised forms of cholesterol implicated in a wide array of biological functions. The compounds were analysed with LC-MS LTQ-Orbitrap high resolution system, which provides a highly sensitive and accurate tool for analysis of metabolites. We profiled a sterol content of newborn murine brain and identified a broad spectrum of oxysterols. Some of these compounds are implicated in neurogenesis, a number of other oxysterols derived from desmosterol were identified in brain tissue for the first time. We analysed murine model of human disease arising from reduced ability to produce cholesterol (SLOS). The sterol profile showed an altered level of cholesterol precursors and generally lowered concentration of oxysterols. Next, we moved to analysis of brain lipidome from animals with disrupted mechanisms of cholesterol metabolism. Cholesterol hydroxylase Cyp46al provides the mechanism of cholesterol removal from the brain. The study of the knock out mice did not reveal the existence of any compensatory mechanisms. The results showed mainly the reduction in cholesterol synthesis. We profiled a sterol content of Cyp27al-/- mouse brain. Cyp27al participates in bile acid synthesis. The steroid profile revealed changed pattern of mono- and polihydroxylated sterols suggesting an upregulation of an alternative pathway of bile acid synthesis. We also analysed the consequence of deficiency of another enzyme involved in bile acids synthesis Cyp7bl. In brain of Cyp7bl-/- mouse we found elevated levels of known Cyp7bl substrates, and increased concentration of other, putative substrates for this enzyme. The last experimental chapter concentrates on analysis of murine macrophages treated with interferon beta and gamma. The treatment induced an increased production of 25-hydroxycholesterol. This links sterol metabolism with mechanisms of immune defence.
Faculty of Medicine, Health and Life Sciences