Sakashita A, Epstein C J, Carlson E, Koeffler H P
Division of Hematology/Oncology, Cedars-Sinai Medical Center, UCLA School of Medicine 90048.
J Cell Physiol. 1994 Aug;160(2):233-8. doi: 10.1002/jcp.1041600204.
The mechanism of growth inhibition mediated by tumor necrosis factor (TNF) is unclear. Since recent data strongly suggested that generation of superoxide is a key step in cytotoxicity of TNF, we reasoned that cells expressing high levels of enzymes that degrade superoxide radicals would be resistant to TNF. Therefore, we examined the TNF-sensitivity of bone marrow progenitor cells of transgenic mice that expressed the gene for human copper zinc-superoxide dismutase (CuZn-SOD). The CuZn-SOD is a key enzyme in the metabolism of superoxide radicals. Heterozygous and homozygous transgenic mice had 3- and 5-fold increased levels of CuZn-SOD activity, respectively. Bone marrow cells of transgenic and nontransgenic mice were plated in soft gel culture with TNF (0.01-100 ng/ml). TNF inhibited myeloid colony formation supported by either granulocyte-macrophage colony-stimulating factor (GM-CSF) or G-CSF from nontransgenic mice in a dose-dependent manner. In contrast, the myeloid clonal growth of homozygote transgenic mice was not inhibited by TNF at concentrations up to 100 ng/ml. As expected, the effects of TNF on erythroid clonogenic cells, which do not produce superoxide, and the action of transforming growth factor-beta on myeloid progenitor cells, were similar in both transgenic and nontransgenic mice. These results suggest that the mechanism of TNF-mediated growth inhibition of hematopoietic cells occurs through production of superoxide.
肿瘤坏死因子（TNF）介导的生长抑制机制尚不清楚。由于最近的数据强烈表明超氧化物的产生是TNF细胞毒性的关键步骤，我们推测，表达高水平降解超氧化物自由基酶的细胞对TNF具有抗性。因此，我们检测了表达人铜锌超氧化物歧化酶（CuZn-SOD）基因的转基因小鼠骨髓祖细胞对TNF的敏感性。CuZn-SOD是超氧化物自由基代谢中的关键酶。杂合子和纯合子转基因小鼠的CuZn-SOD活性水平分别提高了3倍和5倍。将转基因和非转基因小鼠的骨髓细胞接种在含有TNF（0.01 - 100 ng/ml）的软凝胶培养基中。TNF以剂量依赖性方式抑制非转基因小鼠中由粒细胞-巨噬细胞集落刺激因子（GM-CSF）或G-CSF支持的髓系集落形成。相比之下，浓度高达100 ng/ml的TNF对纯合子转基因小鼠的髓系克隆生长没有抑制作用。正如预期的那样，TNF对不产生超氧化物的红系克隆形成细胞的作用，以及转化生长因子-β对髓系祖细胞的作用，在转基因和非转基因小鼠中是相似的。这些结果表明，TNF介导的造血细胞生长抑制机制是通过超氧化物的产生来实现的。
