Role of hydrogen peroxide generated endogenously in myeloid cells

髓样细胞具有多种抵御外部损伤的功能，如细菌感染。这些细胞会产生过氧化氢（H2O2）和次氯酸（HOCl），这是一种更有效的杀微生物剂。因此，过氧化氢在宿主抵御多种微生物方面起着关键作用。然而，H2O2水平的升高可能导致HOCl的过量产生，而HOCl反过来又对细胞有毒。hl60o是来源于急性早幼粒细胞白血病（M3）患者的细胞系，我们使用hl60o抗H2O2的变异克隆，研究了H2O2在这些细胞中的作用。对比两种细胞的生长曲线，HP100的生长速度明显快于HL60。过氧化氢酶（CAT）刺激HL60细胞生长。进一步的研究发现，与亲本细胞相比，崇高的HP100对γ-辐射和肿瘤坏死因子α (TNFα)具有相对的抗性。H2O2的产生在辐照和TNFα的作用下增加，而在HP100细胞中没有。我们还测定了两种细胞系中凋亡相关蛋白的水平。Bax在两种细胞系中均有组成性表达。另一方面，Bcl-2在HP100细胞中表达，而在HL60细胞中不表达。然而，暴露于H2O2、γ射线或tnf - α均未观察到蛋白质水平的变化。这些结果表明H2O2可能通过独立于Bax/Bcl-2途径在HL60细胞中发生凋亡。为了进一步研究这些细胞的凋亡机制，我们比较了h2o2相关基因的表达。HP100细胞的CAT和c-myc mrna水平明显高于HL60细胞。锰超氧化物歧化酶（MnSOD）、谷胱甘肽过氧化物酶（GSH-Px）和CuZnSOD mrna水平在两种细胞系之间无差异。γ射线、TNFα或H2O2均能增加HL60细胞中MnSOD和TNFα转录本的水平，但对HP100细胞没有影响。我们的研究结果表明，内源性产生的H2O2在HL60细胞的生长中发挥了一定的作用。我们还得出结论，辐照和TNFa诱导细胞凋亡，至少部分是通过H2O2的产生；MnSOD或TNFα水平升高而CAT或GSH-Px水平不升高也可能导致H2O2的积累，从而导致细胞凋亡。少

Myeloid cells have various functions against external insults such as bacterial infection. In response to the insults, these cells generate hydrogen peroxide (H2O2) and hypochlorous acid (HOCl), a more potent microbicidal agent. Thus, hydrogen peroxide plays a key role in host defense against a variety of microorganisms. However, elevated levels of H2O2 may lead to overproduction of HOCl, which is, in turn, toxic to the cells. The HL6O is a cell line derived a patient with acute promyelocytic leukemia (M3), and using a variant clone of HL6O that is resistant to H2O2, we studied the role of H2O2 in these cells. When the growth curves of both cell tines were compared, the HP100 grew significantly faster than the HL60. Treatment of the HL60 cells with catalase (CAT) stimulated their cell growth. Further studies found that a sublime HP100 was relatively resistant to γ- irradiation and tumor necrosis factor α (TNFα) as compared to the parent cells. The increased production of H2O2 was seen … More in response to irradiation and TNFα in HL60 cells but not in HP100 cells. We also determined the levels of apoptosis-related proteins in both cell lines. The Bax was constitutively expressed in both cell lines. On the other hand, Bcl-2 was expressed in the HP100 cells but not in the HL60. However, no changes in the levels-of proteins were observed upon exposure to-either H2O2, γ-ray, or TNFα. These results suggest that apoptosis by H2O2 may occur through an independent of Bax/Bcl-2 pathway in the HL60 cells. To investigate further mechanisms for apoptosis in these cells, we compared the expression of H2O2-related genes. HP100 cells had much higher levels of CAT and c-myc mRNAs than HL60 cells. No difference in the levels of manganese superoxide dismutase (MnSOD), glutathione peroxidase (GSH-Px), and CuZnSOD mRNAs were observed between the two cell lines. Treatment with either γ-ray, TNFα, or H2O2 increased the levels of MnSOD and TNFα transcripts dose-dependently in the HL60 cells but did not affect those in the HP100 cells. Our findings suggest that endogenously produced H2O2 plays some role in the growth of the HL60 cells. We also conclude that irradiation and TNFa induce apoptosis through, at least in part, the generation of H2O2 ; increased levels in MnSOD or TNFα but not in CAT or GSH-Px may also lead to the accumulation of H2O2, which results in apoptosis. Less