The onlive version of this article has a Supplementary Appendix. BackgroundExposure to g-radiation causes rapid hematopoietic cell apoptosis and bone marrow suppression. However, there are no approved radiation countermeasures for the acute radiation syndrome. In this study, we demonstrated that natural d-tocotrienol, one of the isomers of vitamin E, significantly enhanced survival in total body lethally irradiated mice. We explored the effects and mechanisms of d-tocotrienol on hematopoietic progenitor cell survival after g -irradiation in both in vivo and in vitro experiments. Design and Methods CD2F1 mice and human hematopoietic progenitor CD34+ cells were treated with d-tocotrienol or vehicle control 24 h before or 6 h after g-irradiation. Effects of d-tocotrienol on hematopoietic progenitor cell survival and regeneration were evaluated by clonogenicity studies, flow cytometry, and bone marrow histochemical staining. d-tocotrienol and g-irradiation-induced signal regulatory activities were assessed by immunofluorescence staining, immunoblotting and short-interfering RNA assay. + cells from radiation-induced damage. d-tocotrienol activated extracellular signal-related kinase 1/2 phosphorylation and significantly inhibited formation of DNA-damage marker g-H2AX foci. In addition, d-tocotrienol up-regulated mammalian target of rapamycin and phosphorylation of its downstream effector 4EBP-1. These alterations were associated with activation of mRNA translation regulator eIF4E and ribosomal protein S6, which is responsible for cell survival and growth. Inhibition of extracellular signalrelated kinase 1/2 expression by short interfering RNA abrogated d-tocotrienol-induced mammalian target of rapamycin phosphorylation and clonogenicity, and increased g-H2AX foci formation in irradiated CD34 + cells. ConclusionsOur data indicate that d-tocotrienol protects mouse bone marrow and human CD34 + cells from radiation-induced damage through extracellular signal-related kinase activation-associated mammalian target of rapamycin survival pathways.Key words: g-tocotrienol, radioprotection, Erk, mTOR. Haematologica 2010;95(12):1996. doi:10.3324/haematol.2010 This is an open-access paper. © F e r r a t a S t o r t i F o u n d a t i o n
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