Hematopoietic Recovery and Amelioration of Radiation-Induced Lethality by the Vitamin E isoform δ-Tocotrienol

delta-Tocotrienol (DT3), a vitamin E isoform, is associated with strong antioxidant and immunomodulatory properties. We confirmed the potent antioxidant activity in membrane systems and showed that DT3 is an effective radiation protector and mitigator. DT3 (4 mu M, P < 0.001) inhibited lipid peroxidation in mouse liver microsomes and nitric oxide (NO) formation (20 mu M DT3, P < 0.01) in RAW264.7 cells, a murine alveolar macrophage line. In CD2F1 mice exposed to lethal total-body radiation from a (60)Co gamma-radiation source, a single subcutaneous (s.c.) injection of DT3 before or after irradiation produced a significant increase in 30-day survival. DT3 was effective from 18.75 to 300 mg/kg (-24 h, P < 0.001). A single dose of 150 or 300 mg/kg DT3 given 24 h before irradiation (radioprotection) resulted in dose reduction factors (DRFs) of 1.19 and 1.27, respectively (P < 0.001). Further, DT3 reduced radiation lethality when administered 2, 6 or 12 h after irradiation, and 150 mg/kg DT3 administered 2 h after exposure conferred a DRF of 1.1 (mitigation). The optimum schedule of 300 mg/kg DT3 24 h prior to 7 Gy significantly reduced pancytopenia compared to irradiated controls (P < 0.05). The large therapeutic potential of and multi-lineage hematopoietic recovery for DT3 warrants further studies. (C) 2011 by Radiation Rowarch Society