tocotrienol--alpha and Stroke

α-Tocotrienol (TCT) represents the most potent neuroprotective form of natural vitamin E that is Generally Recognized As Safe certified by the U.S. Food and Drug Administration. This work addresses a novel molecular mechanism by which α-TCT may be protective against stroke in vivo. Elevation of intracellular oxidized glutathione (GSSG) triggers neural cell death. Multidrug resistance-associated protein 1 (MRP1), a key mediator of intracellular oxidized glutathione efflux from neural cells, may therefore possess neuroprotective functions.. Stroke-dependent brain tissue damage was studied in MRP1-deficient mice and α-TCT-supplemented mice.. Elevated MRP1 expression was observed in glutamate-challenged primary cortical neuronal cells and in stroke-affected brain tissue. MRP1-deficient mice displayed larger stroke-induced lesions, recognizing a protective role of MRP1. In vitro, protection against glutamate-induced neurotoxicity by α-TCT was attenuated under conditions of MRP1 knockdown; this suggests the role of MRP1 in α-TCT-dependent neuroprotection. In vivo studies demonstrated that oral supplementation of α-TCT protected against murine stroke. MRP1 expression was elevated in the stroke-affected cortical tissue of α-TCT-supplemented mice. Efforts to elucidate the underlying mechanism identified MRP1 as a target of microRNA (miR)-199a-5p. In α-TCT-supplemented mice, miR-199a-5p was downregulated in stroke-affected brain tissue.. This work recognizes MRP1 as a protective factor against stroke. Furthermore, findings of this study add a new dimension to the current understanding of the molecular bases of α-TCT neuroprotection in 2 ways: by identifying MRP1 as a α-TCT-sensitive target and by unveiling the general prospect that oral α-TCT may regulate miR expression in stroke-affected brain tissue.

Topics: Animals; Antioxidants; Brain Ischemia; Cell Death; Cerebral Cortex; Male; Mice; Multidrug Resistance-Associated Proteins; Neurons; Neuroprotective Agents; Stroke; Tocotrienols; Vitamin E

The current work is based on our previous finding that in neuronal cells, nmol/L concentrations of alpha-tocotrienol (TCT), but not alpha-tocopherol (TCP), blocked glutamate-induced death by suppressing early activation of c-Src kinase and 12-lipoxygenase.. The single neuron microinjection technique was used to compare the neuroprotective effects of TCT with that of the more widely known TCP. Stroke-dependent brain tissue damage was studied in 12-Lox-deficient mice and spontaneously hypertensive rats orally supplemented with TCT.. Subattomole quantity of TCT, but not TCP, protected neurons from glutamate challenge. Pharmacological as well as genetic approaches revealed that 12-Lox is rapidly tyrosine phosphorylated in the glutamate-challenged neuron and that this phosphorylation is catalyzed by c-Src. 12-Lox-deficient mice were more resistant to stroke-induced brain injury than their wild-type controls. Oral supplementation of TCT to spontaneously hypertensive rats led to increased TCT levels in the brain. TCT-supplemented rats showed more protection against stroke-induced injury compared with matched controls. Such protection was associated with lower c-Src activation and 12-Lox phosphorylation at the stroke site.. The natural vitamin E, TCT, acts on key molecular checkpoints to protect against glutamate- and stroke-induced neurodegeneration.

Topics: Animals; Antioxidants; Arachidonate 12-Lipoxygenase; Brain; Cell Death; Cell Line; Cell Survival; Cells, Cultured; Cerebral Cortex; CSK Tyrosine-Protein Kinase; Fluoresceins; Glutamic Acid; Hippocampus; Immunohistochemistry; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neurons; Neuroprotective Agents; Organic Chemicals; Phosphorylation; Protein-Tyrosine Kinases; Proto-Oncogene Proteins pp60(c-src); Random Allocation; Rats; Rats, Inbred SHR; src-Family Kinases; Stroke; Time Factors; Tocotrienols; Transfection; Tyrosine; Vitamin E