Spin trap protection from tumor necrosis factor cytotoxicity.

Tumor necrosis factor (TNF) facilitates superoxide production, and spin traps may detoxify superoxide by acting as superoxide dismutase mimics. We investigated the ability of a stable nitroxide spin trap, TEMPOL, to protect TNF-sensitive cells from exogenously added TNF. WEHI or L929 cells were incubated with TNF (500 units/ml) for 18 hr either simultaneously with 0 to 8 mM TEMPOL or with the TEMPOL added at varying intervals after TNF exposure. A dose-dependent increase in survival was noted in the TEMPOL-treated cells, with 92 +/- 2% survival of WEHIs treated with 4 mM TEMPOL compared to 26 +/- 1% survival for non-TEMPOL-exposed cells (P2 less than 0.01). Significant increases in survival could be accomplished with as late as 15-hr delayed addition of the compound. The mechanism of protection does not seem to involve newly synthesized protein, and Northern blot analysis revealed that TEMPOL does not induce the genes for MnSOD or Cu-ZnSOD. The ability of TEMPOL to protect against TNF injury, even when exposure is delayed, may prove useful in conditions thought to be associated with free radical-lymphokine interactions such as ischemia-reperfusion, oxygen toxicity, or sepsis.