Vitamin E, an essential constituent of the nervous system: Uptake by brain endothelial cells, transfer across the blood-brain barrier and potential impact on brain-specific gene expression

Free radicals are highly reactive species and can cause oxidative damage to any cellular compartment. In either acute or chronic inflammatory conditions an excessive production of free radicals (e.g.O2 and products generated therefrom) or insufficient detoxification can injure cells and ultimately kill them. This scenario has been put forward as a possible pathological mechanism being responsible for neuronal death in different neurological conditions, although it is not clear whether the production of free radicals is cause or effect of neurodegeneration. However, the fact that Vitamin E (alpha-Tocopherol; alpha-TocH) deficiency causes neurological symptoms-which are indistinguishable from Friedreich`s ataxia provides clear-cut evidence that a sufficient supply of the brain with this potent lipid-soluble chain-breaking antioxidant is absolutely essential for normal neurological function. Despite the necessity of a constant and adequate supply of brain with alpha-TocH, the underlying uptake mechanisms across the blood-brain barrier (BBB) and properties of alpha-TocH beyond the classical antioxidant function in the brain are poorly understood. Therefore the specific aims of the present application are: - To investigate the quantitative contribution of LDL and HDL to overall alpha-TocH uptake across an in vitro porcine BBB model - To elucidate whether the BBB is capable to discriminate between different synthetic alpha-TocH stereoisomers - To clarify the role of different lipoprotein receptors and/or non-specific lipoprotein-binding proteins during transcytosis of lipoprotein-associated alpha-TocH at the BBB - To test the effects of alpha-TocH during assembly of the microglia NADPH-oxidase, an enzyme responsible for cerebral superoxide (O2 )production - To identify genes whose expression in brain is differentially regulated by alpha-TocH We believe that the outcome of the proposed experiments will provide new and useful information on alpha-TocH- uptake, transport and functions in the brain. The differential display approach could provide new and important insights in alpha-TocH-regulated gene expression, a role for alpha-TocH which lies far beyond its classical function as an antioxidant.