Ethanol and cholesterol homeostasis in the brain

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DESCRIPTION (provided by applicant): This proposal for an "exploratory/developmental research grant" (R21) will address a novel aspect of ethanol's developmental neurotoxicity i.e. its effect on cholesterol homeostasis in astrocytes. While too much cholesterol may be deleterious as in case of atherosclerosis and Alzheimer's disease, too little can engender birth defects. Different degrees of mental retardation are often observed in documented inborn errors of cholesterol synthesis such as Smith-Lemli-Opitz syndrome, as well as in the maternal phenylketonuria, were the accumulating metabolite, phenylacetate, is an inhibitor of cholesterol synthesis. Lack of cholesterol during brain development as a consequence of these genetic defects leads, among others, to severe brain damage including microcephaly and mental retardation, both of which are hallmarks of fetal alcohol syndrome. The effect of ethanol on cholesterol homeostasis in the developing brain has not been investigated. Astrocytes produce most of the brain cholesterol which is used for proliferation or is released, via astrocyte-secreted high density lipoprotein-like particles containing apolipoprotein E, outside the cell where it is taken up and utilized by neurons for dendrite outgrowth and to form synapses. Specific aims of the proposal are to investigate the effects of ethanol on the following aspects of cholesterol homeostasis in rat E16, E21, and P6 astrocytes: 1. The effect of ethanol on the "de novo" synthesis and esterification of cholesterol. 2. The effect of ethanol on cholesterol trafficking. 3. The effect of ethanol on apolipoprotein E levels and release and on lipoprotein release and composition. Altogether these studies will provide indication of whether ethanol affects cholesterol homeostasis in astrocytes. If one or more of these end-points are affected by ethanol, further studies will be directed to better understand the mechanism(s) affected by ethanol and to explore the functional consequences of this effect on the developing brain.