The redox-sensitive transcription factor Nrf2 regulates murine hematopoietic stem cell survival independently of ROS levels

Several studies have found that high levels of reactive oxidative species (ROS) are associated with stem cell dysfunction. In the present study, we investigated the role of nuclear factor erythroid-2-related factor 2 (Nrf2), a master regulator of the antioxidant response, and found that it is required for hematopoietic stem progenitor cell (HSPC) survival and myeloid development. Although the loss of Nrf2 leads to increased ROS in most tissues, basal ROS levels in Nrf2-deficient (Nrf2^-/-) BM were not elevated compared with wild-type. Nrf2^-/- HSPCs, however, had increased rates of spontaneous apoptosis and showed decreased survival when exposed to oxidative stress. Nrf2^-/- BM demonstrated defective stem cell function, as evidenced by reduced chimerism after transplantation that was not rescued by treatment with the antioxidant N-acetyl cysteine. Gene-expression profiling revealed that the levels of prosurvival cytokines were reduced in Nrf2 ^-/- HSPCs. Treatment with the cytokine G-CSF improved HSPC survival after exposure to oxidative stress and rescued the transplantation defect in Nrf2^-/- cells despite increases in ROS induced by cytokine signaling. These findings demonstrate a critical role for Nrf2 in hematopoiesis and stem cell survival that is independent of ROS levels.