Canbolat O, Fandrey J, Jelkmann W
Institute of Physiology, Medical University of Luebeck, Germany.
Respir Physiol. 1998 Nov;114(2):175-83. doi: 10.1016/s0034-5687(98)00080-2.
Erythropoietin (Epo) synthesis is suppressed in normoxia and stimulated in hypoxia. To test the hypothesis that the cellular H2O2 level is important in the control of Epo synthesis, we have studied effects of modulators of H2O2 generation and degradation on Epo production in human hepatic cell cultures (hepatoma lines HepG2 and Hep3B). In addition, we measured the activities of antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase) in cultures following hypoxia exposure or H2O2 treatment. The results show that the formation of immunoreactive Epo was stimulated in normoxic cultures by treatment with exogenous catalase thus mimicking the effect of hypoxia (24 h incubation periods). Epo production was also stimulated when scavengers of reactive O2 species (tetramethylthiourea, dihydrorhodamine) were added to the cells. On the other hand, stimulators of H2O2 generation (xanthine oxidase, glucose oxidase, NADH, NADPH) lowered Epo production in hypoxic cultures. Hypoxia exposure decreased superoxide dismutase activity and H2O2 treatment reduced catalase activity thus influencing the endogenous antioxidant defense system. These findings support the concept that reactive O2 species, primarily H2O2, act as messengers in the O2-dependent control of the hepatic production of Epo. Changes in the cellular activities of antioxidant enzymes appear to play only a minor role in this process.
在正常氧条件下，促红细胞生成素（Epo）的合成受到抑制，而在低氧条件下则受到刺激。为了验证细胞内过氧化氢（H₂O₂）水平在Epo合成控制中起重要作用这一假说，我们研究了H₂O₂生成和降解调节剂对人肝细胞培养物（肝癌细胞系HepG2和Hep3B）中Epo产生的影响。此外，我们测量了低氧暴露或H₂O₂处理后培养物中抗氧化酶（过氧化氢酶、超氧化物歧化酶、谷胱甘肽过氧化物酶）的活性。结果表明，在用外源性过氧化氢酶处理的正常氧培养物中，免疫反应性Epo的形成受到刺激，从而模拟了低氧的作用（24小时孵育期）。当向细胞中添加活性氧清除剂（四甲基硫脲、二氢罗丹明）时，Epo的产生也受到刺激。另一方面，H₂O₂生成刺激剂（黄嘌呤氧化酶、葡萄糖氧化酶、NADH、NADPH）降低了低氧培养物中Epo的产生。低氧暴露降低了超氧化物歧化酶的活性，H₂O₂处理降低了过氧化氢酶的活性，从而影响了内源性抗氧化防御系统。这些发现支持了这样一种观点，即活性氧，主要是H₂O₂，在肝脏Epo产生的氧依赖性控制中充当信使。抗氧化酶的细胞活性变化在这一过程中似乎只起次要作用。
