Abstract
[Objective] X-irradiation generates cellular reactive oxygen species (ROS). Transcriptional factor NF-E2-related factor 2 (Nrf2) regulates the expression of multiple antioxidant enzymes, including NAD(P)H-quinone oxidoreductase 1 (NQO1) and heme oxygenase 1 (HO-1). This study investigated whether the induction of HO-1 and NQO1 via Nrf2 is associated with individual differences in the radiosensitivity of human hematopoietic progenitor cells (hHPCs).
[Material and Methods] Human peripheral blood mononuclear cells (hPBMCs) were separated from the buffy-coat by centrifugation on a cushion of Lymphosepar I. X-irradiated hPBMCs (0, 0.2, 0.5, 2 Gy) were cultured in a methylcellulose medium with a combination of cytokines (G-CSF, GM-CSF, IL-3, SCF and EPO). After 14 days of culture, the colonies containing ≥ 50 cells were counted as hHPCs. CD14+ cells (monocytes) were isolated from hPBMCs using an I-Mag separation kit. Total RNA was extracted from the X-irradiated CD14+ cells cultured with cytokines. The expression of HO-1 and NQO1 were assayed by quantitative RT-PCR.
[Results and Discussion] A significant correlation was observed between the HO-1 and NQO1 expressions in hPBMCs monocytes. A positive correlation was observed between the levels of HO-1 and the surviving fraction of hPBMCs exposed to 0.5 Gy. However, no correlation was observed in either the HO-1 expression in hHPCs exposed to 0.2 Gy and 2 Gy or in the levels of NQO1. These data suggest that the expression of Nrf2 depends on individual differences in the responses of hHPCs exposed to 0.5 Gy.
