The effect of macrophage development on the release of reactive oxygen intermediates and lipid oxidation products, and their ability to induce oxidative DNA damage in mammalian cells.

Abstract

Inflammation and the release of potentially damaging substances, such as reactive oxygen intermediates (ROI) and lipid oxidation products from inflammatory cells, have been linked to the potentiation of carcinogenesis. Murine macrophages when stimulated with phorbol esters induce 5,6 ring saturated thymine residues (T'), a lesion of known oxidative origin, in co-cultivated mammalian cells. Induction of this damage was inhibited by catalase and induced in target cells by reagent H2O2 alone. In the present studies, we used defined populations of macrophages with high, low and intermediate capacities for the release of H2O2 or metabolites of arachidonic acid (AA) to assess the relative contribution of these classes of compounds to the induction of saturated thymines. Macrophages activated with Bacillus Calmette-Guerin (BCG), which have the highest capacity for the release of H2O2 and the lowest for the release of metabolites of AA, induced the lowest levels of saturated thymines. Resident macrophages from the unmanipulated peritoneum, which have the lowest capacity for the production of H2O2 and the highest capacity for release of AA metabolites, induced more saturated thymines than did the BCG macrophages. Inflammatory macrophages elicited by casein, which have an intermediate capacity for release of H2O2 and AA metabolites, induced the highest level of saturated thymines. Zymosan, which induced more release of AA metabolites than release of H2O2, was a better stimulant for the induction of T' than TPA, which is a better stimulant for secretion of H2O2. Nordihydroguaiaretic acid (NDGA), an inhibitor of the lipoxygenase and cyclooxygenase pathways for metabolism of AA, inhibited the induction of T' by resident macrophages. Indomethacin, an inhibitor of the cyclo-oxygenase path, enhanced induction of T'. Taken together, the data suggest that while H2O2 has the capacity to induce T' in 3T3 cells, it may not be the only mediator of DNA damage and that lipoxygenase generated metabolites of AA may (alone or in concert with ROI) play an important role in the induction of oxidative DNA damage by macrophages.