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Tocopheryl phosphate, a novel natural form of vitamin E: in vitro and in vivo studies
Author(s) -
Azzi Angelo
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.lb79-d
Subject(s) - vitamin e , tocopherol , chemistry , phosphate , alkaline phosphatase , tocopheryl acetate , phosphorylation , biochemistry , phosphatase , phosphatidylinositol , in vitro , in vivo , enzyme , biology , antioxidant , microbiology and biotechnology
Tocopheryl phosphate (TP) has been found to be present in a number of tissues as well as foodstuffs. When added to smooth muscle cells in vitro, TP exhibits higher growth inhibition potency relatively to alpha tocopherol (T). The same stronger inhibition is observed in CD36 expression. TP inhibits PMA induced superoxide production in macrophages at lower concentrations than AT. If AT is incubated with digitonin permeabilized smooth muscle cells or macrophages, addition of [32P]ATP results in the synthesis of [32P]‐tocopherol. Tocopheryl phosphate has been shown to be hydrolyzed by alkaline phosphatase at a rate of 1/1000 relative to p‐nitro‐phenyl‐phosphate. In a rabbit model of atherosclerosis (2% cholesterol in the diet) TP (0.3–1.33 mg/kg diet) diminishes the amount of the atherosclerotic plaque of more than 60%, while tocopheryl acetate was only about 20% protective. In plasma of animals supplemented with tocopheryl acetate, tocopherol concentration was highly. In animals supplemented with tocopheryl phosphate plasma concentration of tocopherol was low while that of tocopheryl phosphate was high. The hypothesis will be discussed that tocopherol acts at the cellular level after phosphorylation to tocopheryl‐phosphate. Such a reaction implies the existence of a kinase and of a phosphatase to dephosphorylate it. A possible interference of T phosphorylation with the phosphorylation of inositol derivatives and a possible molecular mechanism of TP similar to that of phosphatidylinositol phosphates will be also considered.