5-Androstenediol Promotes Survival of Gamma-Irradiated Human Hematopoietic Progenitors Through Induction of NF-kappa B Activation and G-CSF Expression

5-Androstenediol stimulates hematopoiesis and enhances survival in animals exposed to ionizing radiation IR, suggesting this steroid may act on hematopoietic progenitor cells. We used gamma-irradiated primary human CD34 hematopoietic progenitor cells to show 5-AED protects hematopoietic cells from IR damage, as shown by enhanced cell survival clonogenicity, proliferation, and differentiation. Unlike in tumor cells, IR did not induce NF-kappa BNFkB activation in primary progenitors. However, IR stimulated IkBsub Beta release from NFkBIkB complexes and caused NFkB1 p50 degradation. 5-AED stabilized NFkB1 in irradiated cells, as well as inducing NFkB gene expression and NFkB activation DNA binding. 5-AED stimulated interleukin-6 IL-6 and granulocyte colony-stimulating factor GCSF secretion. The survival-enhancing effects of 5-AED on clonogenic cells were abrogated by siRNA inhibition of NFkB gene expression, and also by neutralization of G-CSF with antibody. The effects of 5-AED on survival and G-CSF secretion were blocked by the NFkB inhibitor MG132. 5-AED had no effect on accumulation of the pro-apoptotic factor p53 after IR, as determined by Western blot. The results indicate that NFkB1 degradation after IR may be responsible for the radiation sensitivity of CD34 cells, as compared to tumor cells. 5-AED exerts survival-enhancing effects on irradiated human hematopoietic progenitor cells via induction, stabilization, and activation of NFkB, which results in increased secretion of hematopoietic growth factor G-CSF.