Effect of long-term arsenate treatment on erythropoietin production in HepG2 cells

抄録

Long-term exposure to arsenic may lead to either acute or chronic toxicity, mainly through drinking-water and food. Anemia is one of the major symptoms of chronic arsenic toxicity. Erythropoietin (EPO) is an essential hormone for hematopoiesis and its suppression causes anemia. Previously we reported that 24-hour treatment with arsenate promotes EPO production in HepG2 cells, which are EPO-producing cells. On the other hand, the long-term effects of arsenate on EPO production are unknown. Therefore, in this study we analyzed EPO production in HepG2 cells exposed to a long-term and low concentrations of arsenate. HepG2 cells to which 10μM arsenate was added and passaged for 3 weeks were designated as adapted HepG2 cells. Cells were harvested 24-hours after the addition of the substance promoting EPO production and the level of EPO mRNA was measured using Real-Time RT-PCR. The amount of reactive oxygen species (ROS) was evaluated by the fluorescence microscopy using the ROS indicator. The level of EPO mRNA in adapted cells was significantly lower than that in non-adapted HepG2 cells. Tempol, a ROS scavenger, suppressed the increase in levels of ROS and EPO mRNA by 100 μM arsenate in HepG2 cells. These results suggested that EPO production was suppressed by not increasing ROS production by arsenate addition in adapted cells and it was considered that adaptation to arsenic promoted ROS degradation. Adapted cells are expected to attenuate physiological responses with ROS signaling.