Induction of oxidative DNA damage in U937 cells by TNF or anti-Fas stimulation

TNF and Fas signaling pathways are reported to induce mitochondrial damage associated with production of oxygen radicals. We examined whether such rad ical production elicited detectable nuclear DNA damage in U937 cells follow ing treatment with TNF or with anti-Fas antibodies, Using GC-mass spectrosc opy for analysing base oxidation, several oxidized species increased signif icantly following TNF treatment, whereas anti-Fas resulted in less detectab le oxidative damage using this assay. Cytogenetic analysis showed that, in the presence of aphidicolin, which blocks several types of DNA repair, TNF induced extensive chromosomal damage. Aphidicolin also synergized with TNF and anti-Fas in inducing cell death which was prevented by reducing atmosph eric oxygen or addition of n-acetyl cysteine, a scavenger of oxygen radical s. Thus, several lines of evidence point to the TNF and Fas pathways induci ng extensive oxidative DNA damage and repair, and suggest potential roles f or these pathways in mutagenesis and aging. (C) 2000 Academic Press.