NF-κB family proteins participate in multiple steps of hematopoiesis through elimination of reactive oxygen species

Abstract

To examine the roles for NF-κB family proteins in hematopoiesis, we first expressed dominant negative Rel/NF-κB (IκBSR) in a factor-dependent cell line, Ba/F3. Although IκBSR neither affected thrombopoietin-dependent nor gp130-mediated growth, it suppressed interleukin-3- and erythropoietin-dependent growth at low concentrations. In addition, IκSSR enhanced factor-deprived apoptosis through the accumulation of reactive oxygen species (ROS). When expressed in normal hematopoietic stem/progenitor cells, IκBSR induced apoptosis even in the presence of appropriate cytokines by accumulating ROS. We also expressed IκBSR in an inducible fashion at various stages of hematopoiesis using the OP9 system, in which hematopoietic cells are induced to develop from embryonic stem cells. When IκBSR was expressed at the stage of Flk-1+ cells (putative hemangioblasts), IκBSR inhibited the development of primitive hematopoietic progenitor cells by inducing apoptosis through the ROS accumulation. Furthermore, when IκBSR was expressed after the development of hematopoietic progenitor cells, it inhibited their terminal differentiation toward erythrocytes, megakaryocytes, and granulocytes by inducing apoptosis through the ROS accumulation. These results indicate that NF-κB is required for preventing apoptosis at multiple steps of hematopoiesis by eliminating ROS.