Hematopoietic progenitor cells of transgenic mice with increased copper/zinc-superoxide dismutase activity are resistant to tumor necrosis factor.
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.
Division of Hematology/Oncology, Cedars-Sinai Medical Center, UCLA School of Medicine 90048.
A
A
Sakashita
C J
CJ
Epstein
E
E
Carlson
H P
HP
Koeffler
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004351:Drug Resistance; D005347:Fibroblasts / Q000166:cytology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000502:physiology; D006412:Hematopoietic Stem Cells / Q000201:enzymology*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013482:Superoxide Dismutase