The effect of hemin-induced oxidative stress on erythropoietin production in HepG2 cells

摘要

Erythropoietin (EPO) and iron are both indispensable hematopoietic factors and are often studied in humans and rodents. Iron activates prolyl hydroxylases (PHDs) and promotes the degradation of the α-subunit of hypoxia inducible factor (HIF), which regulates EPO production. Iron also causes oxidative stress. Oxidative stress leads to alterations in the levels of multiple factors that regulate HIF and EPO production. It is thought that iron influences EPO production by altering two pathways, namely PHDs activity and oxidative stress. We studied the differential effect of varying concentrations of hemin, an ironcontaining porphyrin, on EPO production in HepG2 cells. Hemin at 100 mM reduced EPO mRNA expression. The hemininduced reduction of EPO mRNA levels was attenuated at concentrations greater than 200 μMand EPO production increased in the presence of 500 μM hemin. In comparison, protoporphyrin IX, iron-free hemin did not influence EPO mRNA expression. Additionally, malondialdehyde (MDA) concentrations and superoxide dismutase (SOD) activity significantly increased with 300 μM hemin. Importantly, the antioxidant tempol inhibited the hemin-induced (500 μM) increase in EPO mRNA levels. In conclusion, these results suggest that restraint of EPO production by hemin was offset by the promotion of EPO production by hemin-induced oxidative stress at hemin concentrations greater than 300 μM.