Gamma-Tocotrienol Modulates Total-Body Irradiation-Induced Hematopoietic Injury in a Nonhuman Primate Model

Radiation exposure causes acute damage to hematopoietic and immune cells. To date, there are no radioprotectors available to mitigate hematopoietic injury after radiation exposure. Gamma-tocotrienol (GT3) has demonstrated promising radioprotective efficacy in the mouse and nonhuman primate (NHP) models. We determined GT3-mediated hematopoietic recovery in total-body irradiated (TBI) NHPs. Sixteen rhesus macaques divided into two groups received either vehicle or GT3, 24 h prior to TBI. Four animals in each treatment group were exposed to either 4 or 5.8 Gy TBI. Flow cytometry was used to immunophenotype the bone marrow (BM) lymphoid cell populations, while clonogenic ability of hematopoietic stem cells (HSCs) was assessed by colony forming unit (CFU) assays on day 8 prior to irradiation and days 2, 7, 14, and 30 post-irradiation. Both radiation doses showed significant changes in the frequencies of B and T-cell subsets, including the self-renewable capacity of HSCs. Importantly, GT3 accelerated the recovery in CD34(+) cells, increased HSC function as shown by improved recovery of CFU-granulocyte macrophages (CFU-GM) and burst-forming units erythroid (B-FUE), and aided the recovery of circulating neutrophils and platelets. These data elucidate the role of GT3 in hematopoietic recovery, which should be explored as a potential medical countermeasure to mitigate radiation-induced injury to the hematopoietic system.