Received for publication February 28, 2007.
Revised May 1, 2007.
Accepted for publication May 1, 2007.

5-Androstenediol promotes survival of gamma-irradiated human hematopoietic progenitors through induction of NF-kappa B activation and G-CSF expression

Abstract

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 -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-B (NFkB) activation in primary progenitors. However, IR stimulated IkB release from NFkB/IkB 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 (G-CSF) 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.

Key words: NFkappaB, Regulation of gene expression, Apoptosis, Radical intermediates, Stem cells