Vitamin E Neuroprotection: Novel Molecular Mechanisms

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DESCRIPTION (provided by applicant): Vitamin E has potent neuroprotective properties. Historically, this information has been derived entirely from the study of 1-tocopherol. In nature, the vitamin E family consists of eight members categorized as tocopherols (TCP) and tocotrienols (TCT). The American diet is deficient in TCT. TCT is abundant in Asian diet. Studies during the first cycle of this project presented first evidence establishing that 1-TCT, a poorly known form of natural vitamin E, possesses potent neuroprotective properties. At trace concentration (nM) 1- TCT, but not 1-TCP, conferred neuroprotection in vitro as well as in vivo. It is clear that members of the vitamin E family are not redundant with respect to their biological functions. Current debate surrounding the safety and efficacy of 1-TCP warrants a more even look at all functional forms of natural vitamin E. Results of the first cycle led to the hypothesis that 12-lipoxygenase (12-Lox) is central to glutamate- induced neurodegeneration and that 1-TCT regulates inducible 12-Lox in neural cells rescuing the cells from death. Furthermore, we hypothesize that under GSH-deficient conditions (as is seen during numerous neurodegenerative conditions), arachidonic acid (AA) is metabolized by 12-Lox to 12-HPETE which compromises mitochondrial function and causes neural damage. Aim 1 focuses on cellular mechanisms while Aims 2&3 employs genetic models of 12-Lox (12-Lox-/-, Aim 2) as well as vitamin E (TTP-/-, Aim 3; TTP= tocopherol transfer protein) deficiency to test the in vivo relevance of our hypotheses. Aim 1: Establish the significance of 12-Lox in cellular neurodegeneration and the mechanisms sensitive to 1-TCT. Aim 2: Determine the regulation of 12-lipoxygenase pathway in neurodegeneration in vivo. Aim 3: Define the neuroprotective significance of vitamin E in the brain in vivo. The long-term objective is to develop an understanding of the mechanisms underlying 1-TCT- dependent neuroprotection and in that light to test the efficacy of 1-TCT in protecting against neurodegenerative disorders in preclinical and clinical settings. The fact that 1-TCT is not a synthetic drug but a safe natural nutrient consumed by millions of people on a daily basis in Asia makes it a candidate that could be rapidly taken to pre-clinical and clinical studies.NARRATIVE The project seeks to establish 1-tocotrienol, a natural vitamin E poorly present in American diet, as a dietary ingredient effective against stroke-related damage to the neural tissue.