RADIOPROTECTIVE EFFECTS OF (-)-EPIGALLOCATECHIN-3- GALLATE ON HUMAN ERYTHROCYTE/GRANULOCYTE LINEAGES

摘要

Epigallocatechin-3-gallate (EGCg) is widely recognised as a powerful antioxidant and free radical scavenger. This study examined the radioprotective effects of EGCg on human granulopoiesis and erythropoiesis. Highly purified human CD34~+ haematopoietic stem/progenitor cells were prepared from human placental/umbilical cord blood. The cells were exposed to X rays at a dose rate of ～1 Gy min~(-1) and then cultured in a medium supplemented with either granulocyte colony-stimulating factor (G-CSF) or erythropoietin (EPO). EGCg (100 nM) was added to the culture immediately before or after X-irradiation. The concentration of 100-nM EGCg was determined in the authors' previous study. The number of granulocyte and erythro-cyte colonies generated by X-irradiated CD34~+ cells decreased in a dose-dependent manner. Although EGCg addition yielded an ～ 2-fold increase in the proliferation of each haematopoietic progenitor, no significant protective effect was observed in the surviving fraction of granulocyte progenitors (G-CSF alone: D_0= 1.06 Gy, n= 1.14). However, EGCg addition before or after irradiation conferred a significantly higher protective effect on erythrocyte colony formation compared with the control (EPO alone: D_0=0.66 Gy, n = 1.56; EGCg (before): D_0 = 0.43 Gy, n=5.48). EGCg addition before irradiation significantly improved the survival of erythroid progenitors subjected to radiation of <1 Gy. These results suggest that EGCg is more protective of erythropoiesis than granulopoiesis from radiation damage.