Rg. Liu et al., Oxygen free radicals mediate the induction of manganese superoxide dismutase gene expression by TNF-alpha, FREE RAD B, 28(8), 2000, pp. 1197-1205
In this study, the hypothesis that oxygen free radicals act as intracellula
r messengers is examined. Treatment of human oral carcinoma SCC-25 cells wi
th 200 ng/ml human TNF-alpha for 6 h greatly increased manganese superoxide
dismutase (MnSOD) gene expression as detected by western blotting, RT-PCR,
and nuclear run-on experiments. In the presence of the oxygen free radical
spin trapping reagent, 5,5-dimethyl pyrroline-N-oxide (DMPO), the inductio
n of MnSOD gene expression by TNF-alpha was significantly reduced. Electron
paramagnetic resonance experiments showed that the production of oxygen fr
ee radicals was enhanced in TNF-alpha treated cells. Taken together, these
observations suggest that the induction of MnSOD expression by TNF-alpha is
at least partially mediated by intracellular formation of oxygen free radi
cals, and that superoxide is most likely the initiating species involved in
the mediation of MnSOD gene expression by TNF-alpha. (C) 2000 Elsevier Sci
ence Inc.