Fandrey J, Frede S, Ehleben W, Porwol T, Acker H, Jelkmann W
Physiologisches Institut, Universität Bonn, Germany.
Kidney Int. 1997 Feb;51(2):492-6. doi: 10.1038/ki.1997.68.
We have recently proposed a H2O2-generating b-type cytochrome as part of the cellular oxygen sensor that controls O2-dependent erythropoietin (Epo) production in the human hepatocellular carcinoma cell line HepG2. H2O2 could act as an intracellular signaling molecule because its production in HepG2 cells is strictly dependent on the pericellular PO2. High cellular levels of H2O2 inhibit hypoxia-induced Epo production while low levels-as under hypoxic conditions-allow full expression of the Epo gene. Since cobalt chloride (CoCl2) and the iron chelator desferrioxamine (DSF) both mimic the hypoxic induction of Epo production we studied the influence of CoCl2 and DSF on the formation and on the action of reactive O2-species with respect to Epo production. Both chemicals reduced the H2O2-dependent 123-dihydrorhodamine fluorescence in HepG2 cells. The inhibition of Epo production by exogenous H2O2 was completely antagonized by DSF. This might indicate that H2O2 exerts its inhibition through a Fenton type reaction. On the other hand, NADPH and pyrogallol which stimulate the production of O2- inhibited Epo production. CoCl2 antagonized their effects. From our results we propose different sites of interaction with the putative signaling chain for DSF and CoCl2. While DSF appears to reduce the action of the H2O2 molecule, CoCl2 might act further upstream through the induction of H2O2-scavenger systems or by interfering with its production.
我们最近提出，一种产生过氧化氢的b型细胞色素是细胞氧传感器的一部分，该传感器控制人肝癌细胞系HepG2中氧依赖性促红细胞生成素（Epo）的产生。过氧化氢可作为细胞内信号分子，因为其在HepG2细胞中的产生严格依赖于细胞周围的氧分压。细胞内高浓度的过氧化氢会抑制缺氧诱导的Epo产生，而低浓度——如在缺氧条件下——则允许Epo基因充分表达。由于氯化钴（CoCl2）和铁螯合剂去铁胺（DSF）都能模拟缺氧对Epo产生的诱导作用，我们研究了CoCl2和DSF对活性氧形成及其在Epo产生方面作用的影响。这两种化学物质都降低了HepG2细胞中依赖过氧化氢的123 - 二氢罗丹明荧光。外源性过氧化氢对Epo产生的抑制作用被DSF完全拮抗。这可能表明过氧化氢通过芬顿型反应发挥其抑制作用。另一方面，刺激超氧阴离子产生的烟酰胺腺嘌呤二核苷酸磷酸（NADPH）和邻苯三酚抑制了Epo产生。CoCl2拮抗了它们的作用。根据我们的结果，我们提出了DSF和CoCl2与假定信号链相互作用的不同位点。虽然DSF似乎降低了过氧化氢分子的作用，但CoCl2可能通过诱导过氧化氢清除系统或干扰其产生而在更上游发挥作用。
