Modification of DNA Bases in Chromatin of Intact Target Human Cells by Activated Human Polymorphonuclear Leukocytes1

We investigated whether phorbol-12-acetale-13-myristate (PMA)-activated human polymorphonuclear leukocytes (PMNs) induce base modifi cations in target cell DNA in vivo. Human PMNs produced 9.4 ±0.8 (SD) ninol of l M >71(>''cells during 50 min of exposure to 2 ug/ml I'M A and 13.7 ±2.8 iiini)l/l(l'' cells during exposure to I'M V plus 5 uni N;iN,. Neither nonstimulated PMNs, nor PMA alone, nor NaN , alone induced base mod ifications in chromatin-associated DNA of human Ad293 cells above con trol levels, when assayed by gas chromatography/mass spectrometry with selected-ion monitoring. However, a 60-min exposure to 1.7 ±0.4 x 10'' PMNs/ml in the presence of 2 ug/ml PMA induced a 2-3-fold increase in the level of all modified bases detected by gas chromatography/mass spec trometry with selected-ion monitoring. The guanine-derived products 8-hydroxyguanine and 2,6-diamino-4-hydroxy-5-formamidopyrimidine, and the adenine-derived product 4,6-diamino-5-formamidopyrimidine were induced to the highest levels among those bases detected. These data demonstrate that exposure to activated PMNs causes DNA base modifi cations in target cells in vivo typical of those induced by hydroxyl radical attack. The induction of potentially promutagenic modified bases may contribute to the mutagenicity of activated PMNs.