Production and application of novel model animals with an oxidative stress

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Vitamin E (a-tocopherol) is a fat-soluble antioxidant that is transported by plasma lipoproteins in the body. a-tocopherol taken up by the liver with lipoprotein is thought to be re-secreted into the plasma in very low density lipoprotein (VLDL), alpha-tocopherol transfer protein (alphaTTP), which was recently identified as a product of the causative gene for familial isolated vitamin E deficiency, is a cytosolic liver protein and plays an important role in the efficient recycling of plasma vitamin E.Using cell culture system, we found that the secretion of alpha-tocopherol is more efficient in cells expressing alphaTTP than in matched cells lacking alphaTTP.Brefeldin A, which inhibits VLDL secretion by disrupting the Golgi apparatus, has no effect on alpha-tocopherol secretion, indicating that alphaTTP-mediated alpha-tocopherol secretion is not coupled to VLDL secretion. Among other agents tested, only 25-hydroxycholesterol, a modulator of cholesterol metabolism, inhibits alpha-tocoph … More erol secretion. These results suggest that alphaTTP functions to stimulate secretion of cellular alpha-tocopherol into the extracellular medium and that the reaction utilizes a novel non-Golgi mediated pathway which may be linked to cellular cholesterol metabolism or transport. We examined the structural characteristics of vitamin E analogs required for recognition by alphaTTP.Interestingly, there is a linear relationship between the relative affinity and the known biological activity obtained from the rat resorption-gestation assay. Thus the affinity of vitamin E analogs for alphaTTP is one of the critical determinants of their biological activity. alphaTTP is exclusively expressed in the liver, but the message for alphaTTP was detectable at low levels in some rat tissues including brain, spleen, lung and kidney. In the brain, the alphaTTP transcript is detected predominantly in the cerebellar cortex, as revealed by in situ hybridization histochemistry. In the celebellar cortex, the hybridization signals are detected mostly in the Bergmann glial cells. We have recently succeeded in establishing the knock out mice for alphaTTP.The plasma vitamin E level of the mice is almost undetectable and that of heterozygote is about half that of wild type mice. These data clearly demonstrate that alphaTTP is a major determinant of plasma vitamin E level. Less